Tomcat occasionally crashes if you do frequent hot-deploys or if you are running it on a machine with low memory. Every time tomcat crashes someone has to manually restart it, so I wrote a script which automatically detects that tomcat has crashed and restarts it. Here’s the pseudo logic: every few minutes { check tomcat status; if (status is "not running") { start tomcat; } } every few minutes { check tomcat status; if (status is "not running") { start tomcat; } } Here’s a shell script to implement the above logic. It assumes that you are running on a unix/linux system and have /etc/init.d/tomcat* script setup to manage tomcat. Adjust the path to “/etc/init.d/tomcat” in the script below to reflect the correct path on your computer. Sometimes it is called /etc/init.d/tomcat5 or /etc/init.d/tomcat6 depending on your tomcat version. Also make sure that the message “Tomcat Servlet Container is not running.” matches with the message that you get when you run the script when tomcat is stopped. #! /bin/sh SERVICE=/etc/init.d/tomcat STOPPED_MESSAGE="Tomcat Servlet Container is not running." if [ "`$SERVICE status`" == "$STOPPED_MESSAGE"]; then { $SERVICE start } fi #! /bin/sh SERVICE=/etc/init.d/tomcat STOPPED_MESSAGE="Tomcat Servlet Container is not running." if [ "`$SERVICE status`" == "$STOPPED_MESSAGE"]; then { $SERVICE start } fi To run the script every 10 minutes: 1. Save the above script to “/root/bin/recover-tomcat.sh”. 2. Add execute permission: chmod +x /root/bin/recover-tomcat.sh chmod +x /root/bin/recover-tomcat.sh 3. Add this to root’s crontab, type the following as root: crontab -e crontab -e 4. Add the following lines to the crontab: # monitor tomcat every 10 minutes */10 * * * * /root/bin/recover-tomcat.sh # monitor tomcat every 10 minutes */10 * * * * /root/bin/recover-tomcat.sh What if I don’t have /etc/init.d/tomcat* script on my computer? Tomcat creates a pid file, typically in the TOMCAT_HOME/bin directory. This file contains the process id of the tomcat process running on the machine. The pseudo logic in that case would be: if (the PID file does not exist) { // conclude that tomcat is not running start tomcat } else { read the process id from the PID file if (no process that id is running) { // conclude that tomcat has crashed start tomcat } } if (the PID file does not exist) { // conclude that tomcat is not running start tomcat } else { read the process id from the PID file if (no process that id is running) { // conclude that tomcat has crashed start tomcat } } You can implement the above logic as follows. The following is experimental and is merely a suggested way, test it on your computer before using it. # adjust this to reflect tomcat home on your computer TOMCAT_HOME=/opt/tomcat5 if [ -f $TOMCAT_HOME/bin/tomcat.pid ] then echo "PID file exists" pid="`cat $TOMCAT_HOME/bin/tomcat.pid`" if [ "X`ps -p $pid | awk '{print $1}' | tail -1`" = "X"] then echo "Tomcat is running" else echo "Tomcat had crashed" $TOMCAT_HOME/bin/startup.sh fi else echo "PID file does not exist. Restarting..." $TOMCAT_HOME/bin/startup.sh fi # adjust this to reflect tomcat home on your computer TOMCAT_HOME=/opt/tomcat5 if [ -f $TOMCAT_HOME/bin/tomcat.pid ] then echo "PID file exists" pid="`cat $TOMCAT_HOME/bin/tomcat.pid`" if [ "X`ps -p $pid | awk '{print $1}' | tail -1`" = "X"] then echo "Tomcat is running" else echo "Tomcat had crashed" $TOMCAT_HOME/bin/startup.sh fi else echo "PID file does not exist. Restarting..." $TOMCAT_HOME/bin/startup.sh fi Why would tomcat crash? The most common reason is low memory. For example, if you have allocated 1024MB of max memory to tomcat and enough memory is not available on that machine. Other reasons may involve repeated hot-deploys causing memory leaks, rare JVM bugs causing the JVM to crash. From http://www.vineetmanohar.com/2010/06/howto-auto-recover-tomcat-crashes

So you've finished that shiny new website and you want make sure that you and your buddies are in control. Besides the obvious things such as SSL and logging all access, there are a fewest practices for authentication/access that developers recommend. Here are some of the recommendations: Require separate login pages for users and admin using the same DB table. This will prevent XSRF and session-stealing, plus the attacker won't be able to access to admin areas) [Thief Master] Use complex passwords for admin accounts. For example, "uvula{:&:>iuJ", not "12345". Of course, you have to remember it. :) [Developer Art] Introduce an artificial pause between each admin password attempt to prevent brute force attacks. [Lo'oris] Blocking users IP after a number of failed admin login attempts or requiring a CAPTCHA after a failed login (but not the first one, because that's really annoying) will also stop brute force attacks. [Thief Master] If the admin section is in a separate subdirectory, you should consider also adding webserver native authentication to that area (e.g. via .htaccess in Apache). Then an attacker would need both the subdirectory password and the user password. [Thief Master] Consider Second level authentication such as client certificates (e.g. x509 certs), smart cards, cardspace, etc. [JoeGeeky] Restrict access to the admin area. Only allow clients from trusted IPs/Domains. [JoeGeeky] Lock down IPrincipal & Principal-based authorization and make rights immutable and non-enumerable. Also make sure that all authorization assessments are based on the Principal. [JoeGeeky] Set up an email notification system that alerts admins when any rights are upgraded. This will help you catch an attacker that elevates his/her rights. [JoeGeeky] Consider fine-grained rights for admins. Typical Role-Based Security (RBS) approaches are not as safe because some roles will end up with more rights that they need. You should distribute rights based on the exact actions that a admin performs. This could cause a lot of overhead with more diverse admin-types, but it is safer because rights are issued more sparingly. [JoeGeeky] Restrict the creation of further admins and carefully control what admins can do to other admins. It's best to have a locked-down 'super-admin' client. [JoeGeeky] Consider Client Side SSL Certificates or RSA type keyfobs (electronic tokens) for added security. [Daniel Papasian] If you're using using cookies for authentication, use separate cookies for admin and normal pages. One way is to put the admin section on a different domain. [Daniel Papasian] One possibility, if it's practical, is to put the admin site on a private subnet instead of the internet. [John Hartsock] Re-issue auth/session tickets when moving between admin and normal usage contexts of the website. [Richard JP Le Guen] Require equally strong mechanisms (using the above techniques) for basic users so that admins aren't the only ones with highly-secure accounts. [Lo'oris] These tips were gathered in a question by UpTheCreek from StackOverflow.

Neotys, a leader in easy-to-use, cost effective load testing tools for web applications today announced NeoLoad 3.1, the first test solution on the market to incorporate support for new push technologies such as Adobe RTMP or Ajax Push and now supports Java serialization. A new Java serialization module has been added to record and replay applications using the Java object serialization over HTTP. This module is fully compatible with the spring remote framework. New features Push Technologies module RTMP module Java Serialization module Advanced variabilization Alerts thresholds Customized reports > View all the new features. Free Trial Download the NeoLoad v3.1 demo (30-day free trial). More information http://www.neotys.com

Learn the Builder Design Pattern with easy Java source code examples as James Sugrue continues his design patterns tutorial series, Design Patterns Uncovered

Where does the border lie between validation and the processing itself? The question is if those should be even two separate procedures at all. Let's start with something simple like what the default values are. The most of the other Schema languages allow you to specify the default value. But when should the default value be used? What if some external resources are needed for the default value itself, like a database or a different value in the same document? Does the default value really have to be static? Yes that sounds familiar, it is processing already. XML Processing And what about the processing, didn't you ever need to be sure that the input is valid? And there is another common case, when you need to take actions during the processing based on the fact that some part of the document is valid or not. Sometimes you can't determine the variation of invalidness but you need to take some action based upon that. XDefinition merging processing and validation XDefinition is a schema language developed from the beginning with close respect to the natural readability by keeping the form of the XML data source. Designed to be understandable not only for programmers but also to analysts, system architects and all the other parties concerned with the project. This kind of approach leaves no space to misinterpret data description during it's exchange, starting from the architects to database specialists. XDefinition merges the validation and processing of the XML document as much as you need and what is more important if you need. In the example below we show the usage of an external method, based on the information obtained during the validation is called method. An External method could be any static method in the class supplied to the XDefinition processor through it's API. If you find this kind of approach interesting read the article about readability of the schema languages here on the Javalobby called XSD Schema is not the only way or try the Tutorial with examples. Resources: XDefinition guidepost

Learn the State Design Pattern with easy Java source code examples as James Sugrue continues his design patterns tutorial series, Design Patterns Uncovered

A few weeks ago, a co-worker sent me interesting email after talking with the Zoompf CEO at JSConf. One interesting tip mentioned was how we querystring the version on our scripts and css. Apparently this doesn't always cache the way we expected it would (some proxies will never cache an asset if it has a querystring). The recommendation is to rev the filename itself. This article explains how we implemented a "cache busting" system in our application with Maven and the UrlRewriteFilter. We originally used querystring in our implementation, but switched to filenames after reading Souders' recommendation. That part was figured out by my esteemed colleague Noah Paci. Our Requirements Make the URL include a version number for each static asset URL (JS, CSS and SWF) that serves to expire a client's cache of the asset. Insert the version number into the application so the version number can be included in the URL. Use a random version number when in development mode (based on running without a packaged war) so that developers will not need to clear their browser cache when making changes to static resources. The random version number should match the production version number formats which is currently: x.y-SNAPSHOT-revisionNumber When running in production, the version number/cachebust is computed once (when a Filter is initialized). In development, a new cachebust is computed on each request. In our app, we're using Maven, Spring and JSP, but the latter two don't really matter for the purposes of this discussion. Implementation Steps 1. First we added the buildnumber-maven-plugin to our project's pom.xml so the build number is calculated from SVN. org.codehaus.mojo buildnumber-maven-plugin 1.0-beta-4 validate create false false javasvn 2. Next we used the maven-war-plugin to add these values to our WAR's MANIFEST.MF file. maven-war-plugin 2.0.2 true ${project.version} ${buildNumber} ${timestamp} 3. Then we configured a Filter to read the values from this file on startup. If this file doesn't exist, a default version number of "1.0-SNAPSHOT-{random}" is used. Otherwise, the version is calculated as ${project.version}-${buildNumber}. private String buildNumber = null; ... @Override public void initFilterBean() throws ServletException { try { InputStream is = servletContext.getResourceAsStream("/META-INF/MANIFEST.MF"); if (is == null) { log.warn("META-INF/MANIFEST.MF not found."); } else { Manifest mf = new Manifest(); mf.read(is); Attributes atts = mf.getMainAttributes(); buildNumber = atts.getValue("Implementation-Version") + "-" + atts.getValue("Implementation-Build"); log.info("Application version set to: " + buildNumber); } } catch (IOException e) { log.error("I/O Exception reading manifest: " + e.getMessage()); } } ... // If there was a build number defined in the war, then use it for // the cache buster. Otherwise, assume we are in development mode // and use a random cache buster so developers don't have to clear // their browswer cache. requestVars.put("cachebust", buildNumber != null ? buildNumber : "1.0-SNAPSHOT-" + new Random().nextInt(100000)); 4. We then used the "cachebust" variable and appended it to static asset URLs as indicated below. The injection of /v/[CACHEBUSTINGSTRING]/(assets|compressed) eventually has to map back to the actual asset (that does not include the two first elements of the URI). The application must remove these two elements to map back to the actual asset. To do this, we use the UrlRewriteFilter. The UrlRewriteFilter is used (instead of Apache's mod_rewrite) so when developers run locally (using mvn jetty:run) they don't have to configure Apache. 5. In our application, "/compressed/" is mapped to wro4j's WroFilter. In order to get UrlRewriteFilter and WroFilter to work with this setup, the WroFilter has to accept FORWARD and REQUEST dispatchers. rewriteFilter /* WebResourceOptimizer /compressed/* FORWARD REQUEST Once this was configured, we added the following rules to our urlrewrite.xml to allow rewriting of any assets or compressed resource request back to its "correct" URL. ^/v/[0-9A-Za-z_.\-]+/assets/(.*)$ /assets/$1 ^/v/[0-9A-Za-z_.\-]+/compressed/(.*)$ /compressed/$1 /compressed/** /compressed/$1 Of course, you can also do this in Apache. This is what it might look like in your vhost.d file: RewriteEngine on RewriteLogLevel 0! RewriteLog /srv/log/apache22/app_rewrite_log RewriteRule ^/v/[.A-Za-z0-9_-]+/assets/(.*) /assets/$1 [PT] RewriteRule ^/v/[.A-Za-z0-9_-]+/compressed/(.*) /compressed/$1 [PT] Whether it's a good idea to implement this in Apache or using the UrlRewriteFilter is up for debate. If we're able to do this with the UrlRewriteFilter, the benefit of doing this at all in Apache is questionable, especially since it creates a duplicate of code. From http://raibledesigns.com/rd/entry/versioning_static_assets_with_urlrewritefilter

What exactly is an exception? Exceptions are irregular or unusual events that happen in a method the program is calling which usually occurs at runtime. The method throws the Exception back to the caller to show that it is having a problem. If the programmer runs into this case, then they will need to extend an Exception from the Exception class that is already in the Java class library. In Eclipse, on the class declaration panel, the coder and request “constructors from superclass” and it will give the programmer constructors in a child Exception class that will accept error messages or the address of another Exception as a constructor parameter. When creating an Exception class, the programmer has to designate a kind of exception that must be caught or optionally caught. If you declare the Exception class to extend Exception as shown below, the compiler will insist that the method that is being thrown should also be in a caught in catch block. public class CodeName extends Exception { ……. } The compiler gives the programmer two choices when they call a method that throws an Exception that must be caught: 1. Add a try/catch in the code that is being call to catch the Exception 2. Pass the Exception back on to the caller If the programmer chooses option two then they can do this by adding a "throws" clause to end of the method declaration line. The compiler will generate the code to pass the Exception back to the caller at run-time. In the code below, the AnApplcation program is calling a Java Bean object's openFile() method, passing it the file name. The compiler will say to the openFile() method at compile time: "How do you want to handle the Exception?" The AJavaBean should realize there is nothing they can do in the openFile() method to fix the problem so the programmer should throw the Exception back to AnApplication. Eclipse can see the myProgram() in AnApplication is calling the openFile() method and when openFile() adds "throws FileNotFoundException" to its method declaration line, the compiler gives myProgram() method an error message asking the application method how it would like to handle the Exception. public class AnApplication { public void myProgram() { bean.openFile(filename); …… } } public class AJavaBean { public void openFile(String filename) throws FileNotFoundException { file.open(filename); //open() may throw FileNotFoundException …. } } If the programmer choose the first method then they can see below that all the code to process, open, and read are put into a try block. Once a method is called that might throw and Exception, the call has to be from within a try block because there is a chance of failure. If an Exception has been thrown by a method that is called in the try block shown below, the execution jumps out of the try block and into one of the catch blocks. The code that is left below that point in the try block is skipped as you can tell from the structure below. Execution will continue out the bottom of the catch block which branches to the bottom of the catch group if the catch block doesn’t stop the method processing by doing a return. Try/Catch example in Java: public void myProgram() { try { bean.openFile(fileName); // throws FileNotFoundException help.readFileContents(); // throws ReadException do.processFileData(); // throws ProcessException } catch(FileNotFoundException ex) { System.out.println(ex); // calls toString() on ex } catch(ReadException ex) { System.out.println(ex); // calls toString() on ex } catch(ProcessException ex) { System.out.println(ex); // calls toString() on ex } } } What happen if it was really vital that we close the file we open at the top of the try block? If you close it at the bottom of the try block, an exception is thrown and the execution will never get to the bottom of the try block. To guarantee the file gets closed, you would have to repeat the close() action in every one of the catch blocks which becomes repetitive coding. So you could remove all the close() and include a finally block at the bottom like shown below. After the try block has been entered, the finally code will be executed. The finally code will also be executed also if a catch block is entered, even if the catch does a return. public void myProgram() { try { bean.openFile(fileName); // throws FileNotFoundException help.readFileContents(); // throws ReadException do.processFileData(); // throws ProcessException } catch(FileNotFoundException ex) { System.out.println(ex); // calls toString() on ex } catch(ReadException ex) { System.out.println(ea); // calls toString() on ex } catch(ProcessException ex) { System.out.println(ex); // calls toString() on ex } finally { bean.close(filename); } } All the catch blocks print the Exception object’s toString() on the console as an error message. If you are not going to differentiate processing for different kinds of Exceptions, then you could use a “catch-all” block. Since all exception objects are type Exception then they will be directed into this catch block as shown below. Any unanticipated types of exception will be caught also. public void myProgram() { try { bean.openFile(fileName); // throws FileNotFoundException helper.readFileContents(); // throws ReadException do.processFileData(); // throws ProcessException } catch(Exception ex) { System.out.println(ex); // calls toString() on ex } finally { bean.close(filename); } }

Today, a lot of websites have their content provided in feeds that users can subscribe to. Feeds basically are a simplified version of the site content, providing text and media –only representation of the data published on the website. One of the most popular feed formats is RSS and it stands for Really Simple Syndication. It is XML-based and is used by the majority of websites that contain dynamically updated content, like blogs or news resources. Being XML based and having a well-defined structure, it is correct to think that it can be read as a regular XML document and this is absolutely true. However, there is System.Servicemodel.Syndication that can make the feed reading process a bit easier. So let’s look at a specific example. There is the DZone Link Feed, located here: http://feeds.dzone.com/dzone/frontpage?format=xml It’s an easy way to keep up with the upcoming interesting content, so I’d like to integrate this into my application. If I take a look at the source for the feed, I can see content similar to this: http://feeds.dzone.com/~r/dzone/frontpage/~3/wrVQN_7G8Hk/google_web_toolkit_blog_google_maps_api_for_gwt_1.html We are pleased to announce the Google Maps API for the Google Web Toolkit 1.1.0 release. The Google Maps API library provides a way to access the Google Maps API from a GWT project without having to write additional JavaScript code. frameworks java javascript web services Thu, 03 Jun 2010 18:54:42 GMT http://www.dzone.com/links/423703.html @thierry_lefort 2010-06-03T18:54:42Z We are pleased to announce the Google Maps API for the Google Web Toolkit 1.1.0 release. The Google Maps API library provides a way to access the Google Maps API from a GWT project without having to write additional JavaScript code.]]> 423703 2010-06-02T10:12:27Z 2010-06-03T18:54:42Z 6 0 90 0 http://www.dzone.com/links/images/thumbs/120x90/423703.jpg Thierry.Lefort http://www.dzone.com/links/images/avatars/252611.gif http://www.dzone.com/links/rss/google_web_toolkit_blog_google_maps_api_for_gwt_1.html As you can see here, an item is basically a feed entry that contains information about one content entity. Note that there are some site-specific tags that I am not covering here, but that are still readable via XmlDocument. An important note that has to be made here is that .NET (not using any third-party components) only supports RSS 2.0 feeds (I am not including Atom here). To get started, add a reference to System.ServiceModel and System.ServiceModel.Syndication. Now, in the class header, add the statement below: using System.ServiceModel.Syndication; Now you’re all set. Let’s try and read the feed above. To do this, I will need an instance of SyndicationFeed and XmlReader. Here is how the code looks like: SyndicationFeed feed = SyndicationFeed.Load(XmlReader.Create("http://feeds.dzone.com/dzone/frontpage")); This will read the actual feed. And since I mentioned that the feed is composed out of multiple items, all of them are stored in the Items collection. You can go through it via this: foreach (SyndicationItem item in feed.Items) { Debug.Print(item.Title.Text); } The code above will get the titles of each item included in the feed. A question that might arise is why do I have to call the Text property when Title should already be of type string. This is a wrong assumption, since Title in fact is of type TextSyndicationContent, therefore this means that it can contain HTML, XHTML or plain text. Therefore, converting it directly ToString() will not give correct results. For each of the items I can get the summary – a short representation of the published content: foreach (SyndicationItem item in feed.Items) { Debug.Print(item.Summary.Text); } Please remember that item.Summary is not the same as item.Content. As you see in the feed sample I provided, the content is surrounded by CDATA, meaning that it can provide HTML data to the receiving end. If I am going to call item.Content I will get an “Object reference not set to an instance of an object.” due to the fact that it is content:encoded instead of content. To read the content in this case, I am going to use this: foreach (SyndicationItem item in feed.Items) { foreach (SyndicationElementExtension ext in item.ElementExtensions) { if (ext.GetObject().Name.LocalName == "encoded") Debug.Print(ext.GetObject().Value); } } This will prevent the above mentioned exception and will read the string representation of the item content.

Learn the Iterator Design Pattern with easy Java source code examples as James Sugrue continues his design patterns tutorial series, Design Patterns Uncovered

I was converting the example code of my Windows Azure session to Visual Studio 2010 solution called MVC Time Planner when I discovered some date and time offset issues in my JavaScript code. In this posting I will show you some useful tricks you can use to convert JavaScript dates and times to timestamps. Date.getTime() returns UTC When you call getTime method on Date object you get the number of milliseconds from Unix epoch. Although your current Date object keeps time with some offset getTime gives seconds in UTC. Keep this in mind when creating timestamps if you are not living on zero-meridian. var currentDate = selectedDate; // current date with offset var currentTime = currentDate.getTime(); // offset is ignored This is pretty awkward, unexpected and unintuitive behavior but you have to keep in mind that all date and time calculations must use same time system to give appropriate results. Date.getTimezoneOffset() getTimezoneOffset method returns you the amount of minutes you have to add to your current timestamp to convert it to UTC time. If your time zone is UTC+3 then getTimezoneOffset returns you –180 because: UTC + 3 hours + (-180) minutes = UTC If your time zone is UTC-3 then UTC - 3 hours + 180 minutes = UTC Pretty simple math but confusing at first place. Getting timestamp with time zone In my application I have to give timestamp for selected dates and times to server. I need to find correct amount of seconds from Unix epoch so users can save times based on their region and not by UTC. Here is how calculate timestamps. var currentDate = selectedDate; var currentTime = currentDate.getTime(); var localOffset = (-1) * selectedDate.getTimezoneOffset() * 60000; var stamp = Math.round(new Date(currentTime + localOffset).getTime() / 1000); On server side I use the following method to convert timestamp to date. This method is borrowed from CodeClimber blog posting Convert a Unix timestamp to a .NET DateTime. private static DateTime ConvertFromUnixTimestamp(double timestamp) { var origin = new DateTime(1970, 1, 1, 0, 0, 0, 0); return origin.AddSeconds(timestamp); } Conclusion Playing with dates and times is always interesting thing to do because there are many different time zones in the world and supporting them all is not easy thing to do. Inside the system we must be able to keep all dates in appropriate system and usually it is UTC. This posting showed you some tricks about how to play with local times in JavaScript.

Learn the Bridge Design Pattern with easy Java source code examples as James Sugrue continues his design patterns tutorial series, Design Patterns Uncovered

In 2003 the Swedish Defence Research Agency (FOI) started to consolidate work within the simulation domain to use the same simulation framework where applicable. To meet this end, that is, a distributed simulation architecture, the high level architecture (HLA) was selected to ease collaboration between research projects. It soon became clear that a scenario editor and scenario engine were needed to manage distributed simulations. Existing products filling this need, at the time, were either too expensive or not flexible enough for the purpose; a scenario tool needed to be developed. Requirements One requirement for the scenario tool was to use as few licensed software packages as possible and to be able to run on UNIX, Linux, and Windows. For many reasons, Java was the obvious choice to develop this scenario tool. Another requirement for the scenario tool was to have the whole scenario of a simulation in one central location. That includes setup of participating applications in a distributed simulation and which applications should participate. One of the software engineers in the project, Mikael Brännström, had done previous work on a demo using the NetBeans Platform and the decision was made to use the NetBeans Platform as the base for the scenario tool. Scenario Model The central component for a simulation is, of course, the scenario. The type of content in a scenario is described in a scenario model. Both scenario and scenario model can be represented in XML. Below is a representation (click to enlarge it) of a scenario and the simulation-related classes: The Scenario contains the main components of the simulation, entities, paths and coverage diagrams. These objects are persistent and are editable in NetScene. An Entity describes a physical or an abstract part in the simulation, for example a vehicle or a part of a software system. An Entity has a set of attributes, for example position or color. It also contains parameters that describe the relation to the parent, or container, of the entity, for example the relative position and orientation of a camera entity to the human that are carrying the camera. An Entity can have an EntityModel that performs some behavior of the entity. An EntityModel is executed by the SimulationEngine during the simulation and it has full access to the rest of the scenario. An EntityModel can model behavior of the entity, such as motion or sending Messages. A Message is an object used to handle communications between entity models and/or plug-ins, for example a sensor track or A Path contains a number of waypoints. A Path can be used by for example a motion model. Different interpolations can be selected for a path. A CoverageDiagram is used by for example sensor coverage. The scenario model is the scenario palette that hierarchically describes the components which can be used to create a scenario. The scenario model describes: data types: simple or complex entity classes: class hierarchy, attributes, relations between entities and default values message classes: parameters coverage diagram classes: parameters Scenario Creation The top left window contains a representation of the current scenario. It contains all entities, paths and coverage diagrams of the scenario. It also contains those scenarios that are included from the current scenario. The top right window contains scenarios and game configurations. These nodes are identified from the project files with MIME-resolvers. From this window scenarios can be merged or included to the current scenario. A merged scenario simply adds content to the current scenario. An included scenario acts as a reference to the included scenario, enabling several scenarios to be edited in the same context. The bottom left window contains a representation of the current scenario model. Entities and entity models can be dragged and dropped from this window to the middle window to create new entities or to add entity models to existing entities. The bottom right window contains a customizable properties window that can be configured by the user. It also differs from the normal property view in the way that it contains tools for the user to quickly manipulate complex types of the selected node. The middle window contains a map of the current scenario. Several maps can be open at the same time. Maps can be geo-referenced images, WMS maps and 3D maps. These windows also supply several tools for editing the scenario spatially. In part 2, you will read about concept development & experimentation with NetScene, as well as NetScene's plugins, and the applicability of these developments to multi-sensor systems. Now continue to part 2...

In the article, Groovy, Grails and Vaadin, Petter Holmström outlined an example of using Vaadin with Grails, to build a simple data bound UI for a single database table. This was a great article that showed how one can quickly build a web-based solution that behaves very much like a typical client-server application. However, there are many instances where we need to be able to build an entry screen which allows the user to update both the master record and its detail records at the same time, such as in an Invoice entry screen. In this article I looked at extending the example in the above article, leveraging the simplicity of the Vaadin framework and the GORM capabilities, to build a master-detail example. After years of doing development using Oracle Forms, I liked the way it provides generic functions on each form (or data block) to allow users to add new records, delete them, query them and navigate from one record to the next. Furthermore, in Oracle Forms, you could provide a data grid to allow the user to edit the related detail table (such as the invoice lines in an Invoice document) and keeps these records in sync with the Invoice header (master) record. This is a first attempt at reproducing some of these capabilities using Vaadin and Grails. The master-detail data model The example here is an extension of the Petter Holmström model of the Trip Planner. In the original example, there is a table holding information on trips taken by the user. We will extend that example by having a one-to-many relation with a table of the places that are visited in each trip. This is the code for the Trip domain class. Notice that we are using Grails 1.3.1 which, by default, puts the domain class into the tripplanner package. package tripplanner class Trip { static constraints = { name(nullable: true) city(nullable: true) startDate(nullable: true) endDate(nullable: true) purpose(nullable: true) notes(nullable: true) } String name String city Date startDate Date endDate String purpose String notes static hasMany = [ places : Place ] static mapping = { places lazy:false, cascade:"all,delete-orphan" } } We have made the fields nullable for ease of inserting the record into the table. We also created the one-to-many relation with the Place domain class, and put in the mapping to cascade the deletion and updates to the sub-table class. We also need to change the relation from lazy to eager to ensure that the all detail records are loaded at the same time as the master (header) record. As for the Place domain class, we have 2 fields; name of the place we visited and a description field. In addition, we also put in a transient field, "_deleted", hich we will use to mark a detail record for deletion. package tripplanner class Place { static constraints = { name(nullable: true) description(nullable: true) } String name String description boolean _deleted static transients = [ '_deleted' ] static belongsTo = [trip:Trip] } The master-detail form Now, we need to change the VaadinApp class. Instead of listing the master record in a table to be selected for editing, I have opted to follow the Oracle Forms style for letting the user query for master records using Query By Example (QBE). The standard GORM and Hibernate infrastructure allows the use of a "example" object as a query pattern to extract a subset of records. This unfortunately is not exactly how Oracle Forms QBE works as Oracle Forms allows the user to put in "A%" patterns to query for values that starts with "A" and ">999" to query for values that is bigger than 999. The QBE in GORM only allows exact matches. We will accept this limitation for this example. So now we need a set of buttons to allow the user to: New - Add a new record data entry Save - Saves the current record to the database, including the changes done to the detail table Del - Deletes the current master record and the associated detail records EnterQ - Enters into Query mode which allows the user to provide a pattern for a QBE search ExecQ - Executes the Query and shows the first matching record from the query ExitQ - Exits out of Query mode and goes back to New record mode Prev - Go to previous record if there any queried records Next - Go to next record if there are any queried records These buttons are located at the top of the master record form. Error messages which arise from the save / update button are listed at the top of the master record form fields (in the "description field" of the Vaadin Form). There is also a status indicator label located at the footer of the master record form ("footer section" of the Vaadin Form). The status label will show the current mode of the master record entry screen and also the current record number if this is part of a query set. Below the master record form is the editable, selectable detail records table which is located in its own panel. Users are allowed to edit the detail record table only if the master record is in Edit mode. This means that users need to save the newly created master (header) record before that they can add any detail records. The detail record table has a column for all the editable, visible records excluding the "_deleted" field which is for internal use only. To manipulate the detail records, we provide 2 buttons to add a new detail record (the "+" button) or delete the selected detail record (the "-" button). All additions, deletions or even updates are only saved to the database after the user clicks on the "Save" button in the master (header) record form. As the user moves from one master record to the next using the "Prev" and "Next" buttons in the master table form, the detail table will be synchronized accordingly. package tripplanner import com.vaadin.ui.* import com.vaadin.data.* import com.vaadin.data.util.* class VaadinApp extends com.vaadin.Application { def query def rec_pos def container = new BeanItemContainer(Place.class) def master_fields = ["name", "purpose", "startDate", "endDate", "city", "notes"] def saveButton def newButton def delButton def entQButton def exeQButton def extQButton def prevButton def nextButton def statusLabel def pnlDetail void new_mode(editor) { def tripInstance = new Trip() editor.itemDataSource = new BeanItem(tripInstance) editor.visibleItemProperties = master_fields editor.description = "" container.removeAllItems() saveButton.setEnabled(true) delButton.setEnabled(false) entQButton.setEnabled(true) extQButton.setEnabled(false) statusLabel.setValue "New Mode" pnlDetail.setEnabled(false) } void init() { //def window = new Window("Trip Maintenance", new SplitPanel(SplitPanel.ORIENTATION_HORIZONTAL)) def window = new Window("Trip Maintenance") setMainWindow window // Form Panel def panel = new Panel("Trip Maintenance") panel.setSizeFull() panel.setLayout(new VerticalLayout()); // Trip editor def tripEditor = new Form() tripEditor.setSizeFull() tripEditor.layout.setMargin true tripEditor.immediate = true tripEditor.visible = true // status bar - shows the mode of the form statusLabel = new Label("New Mode") // define master form buttons saveButton = new Button("Save") newButton = new Button("New") delButton = new Button("Del") entQButton = new Button("EnterQ") exeQButton = new Button("ExecQ") extQButton = new Button("ExitQ") prevButton = new Button("Prev") nextButton = new Button("Next") // set initial state of buttons delButton.setEnabled(false) extQButton.setEnabled(false) // default is New Mode def v_tripInstance = new Trip() tripEditor.itemDataSource = new BeanItem(v_tripInstance) tripEditor.visibleItemProperties = master_fields //new_mode(tripEditor) // panel for detail form pnlDetail = new Panel() pnlDetail.setEnabled(false) // table to hold the detail form rows def table = new Table() table.containerDataSource = container table.selectable = true table.editable = true table.setSizeFull() table.visibleColumns = ["name", "description"] table.immediate = true // toolbar for the detail form manipulation def toolbar = new HorizontalLayout() // buttons for detail form // button to add new row to detail form def addRowButton = new Button("+", new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { def placeInstance = new Place() def tripInstance = tripEditor.itemDataSource.bean tripInstance.addToPlaces(placeInstance) container.addBean placeInstance } }) toolbar.addComponent addRowButton // button to delete current row from detail form def delRowButton = new Button("-", new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { if (table.value) { def placeInstance = table.value placeInstance._deleted = true container.removeItem(placeInstance) table.value = null } } }) toolbar.addComponent delRowButton // detail panel has the table rows and the toolbar pnlDetail.addComponent toolbar pnlDetail.addComponent table // master form buttons // save record button saveButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { Trip.withTransaction { status -> table.commit() def tripInstance = tripEditor.itemDataSource.bean def _toBeDeleted = tripInstance.places.findAll {it._deleted} if (_toBeDeleted) { tripInstance.places.removeAll(_toBeDeleted) } if (!tripInstance.save(flush:true)) { tripEditor.description = "Error:" tripInstance.errors.allErrors.each { error -> tripEditor.description = tripEditor.description + "" + "Field [${error.getField()}] with value [${error.getRejectedValue()}] is invalid" } tripEditor.description = tripEditor.description + "" window.showNotification "Could not save changes" } else { tripEditor.description = "" window.showNotification "Changes saved" delButton.setEnabled(true) statusLabel.setValue("Edit Mode"); pnlDetail.setEnabled(true) populate_container(container,tripInstance.places) } } } }) // new record button newButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { new_mode(tripEditor) } }) // delete record button delButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { if (tripEditor.itemDataSource.bean) { Trip.withTransaction { status -> def tripInstance = tripEditor.itemDataSource.bean tripInstance.delete(flush:true) } } new_mode(tripEditor) } }) // enter query mode entQButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { def tripInstance = new Trip() def newBean = new BeanItem(tripInstance) tripEditor.itemDataSource = newBean tripEditor.visibleItemProperties = master_fields tripEditor.description = "" saveButton.setEnabled(false) delButton.setEnabled(false) entQButton.setEnabled(false) extQButton.setEnabled(true) statusLabel.setValue("Query Mode"); pnlDetail.setEnabled(false) } }) // execute query exeQButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { tripEditor.commit() def example = (Trip) tripEditor.itemDataSource.bean query = Trip.findAll(example) rec_pos = 0 tripEditor.description = "" entQButton.setEnabled(true) extQButton.setEnabled(false) if (query.size > 0) { def next_rec = query[rec_pos] tripEditor.itemDataSource = new BeanItem(next_rec) tripEditor.visibleItemProperties = master_fields saveButton.setEnabled(true) delButton.setEnabled(true) statusLabel.setValue("Edit Mode. Record " + (rec_pos+1) + "/" + query.size); pnlDetail.setEnabled(true) populate_container(container,next_rec.places) } else { window.showNotification "No record found" new_mode(tripEditor) } } }) // exit query mode. Back to New mode extQButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { new_mode(tripEditor) } }) // edit mode, previous record prevButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { if (!query) { window.showNotification "No query result" return } if (rec_pos > 0) { rec_pos-- def next_rec = query[rec_pos] tripEditor.itemDataSource = new BeanItem(next_rec) tripEditor.visibleItemProperties = master_fields saveButton.setEnabled(true) statusLabel.setValue("Edit Mode. Record " + (rec_pos+1) + "/" + query.size) pnlDetail.setEnabled(true) populate_container(container,next_rec.places) } } }) // edit mode, next record nextButton.addListener(new Button.ClickListener() { void buttonClick(Button.ClickEvent event) { if (!query) { window.showNotification "No query result" return } if (rec_pos < query.size - 1) { rec_pos++ def next_rec = query[rec_pos] tripEditor.itemDataSource = new BeanItem(next_rec) tripEditor.visibleItemProperties = master_fields saveButton.setEnabled(true) statusLabel.setValue("Edit Mode. Record " + (rec_pos+1) + "/" + query.size) pnlDetail.setEnabled(true) populate_container(container,next_rec.places) } } }) // put the status bar on the footer of the master form tripEditor.footer = new HorizontalLayout() tripEditor.footer.addComponent statusLabel // put all master form buttons into a horizontal panel def btnPanel = new HorizontalLayout() btnPanel.addComponent saveButton btnPanel.addComponent newButton btnPanel.addComponent delButton btnPanel.addComponent entQButton btnPanel.addComponent exeQButton btnPanel.addComponent extQButton btnPanel.addComponent prevButton btnPanel.addComponent nextButton // construct master-detail form panel panel.addComponent btnPanel panel.addComponent tripEditor panel.addComponent pnlDetail // set panel to main window mainWindow.addComponent panel } // routine to populate the container with the detail records void populate_container(container, details) { container.removeAllItems() details.each { if (!it._deleted) container.addBean it } } } A walkthrough of the above VaadinApp code is as follows. The query object stores the list of "Trip" instances that is returned from a QBE query. The rec_pos is an index into the above list for the currently displayed record. The master_fields stores the list of master record fields that is visible on the form We put some of the buttons, status label and detail panel object as the object variables so that they can be access by helper routines The new_mode routine is to put the form into the New mode, which occurs multiple times in the whole code The init routine is where the whole window and form is defined The form is laid out with the master record buttons at the top, followed by the master record form, and then the detail table sub-panel below that In the detail sub-panel, there are 2 buttons, "+" and "-" which adds a detail to the Table and the master record instance and removes a detail record, respectively. These are not put into a GORM Transaction as we only want to save (flush) the record when the "Save" button is saved. The really tricky part of the whole form is in the master record buttons. For the "Save" button, we first force the detail table to update the source records in the master collection. Then we delete all the detail records which are marked for deletion, where the "_deleted" field is set to true. Finally the master record is saved by calling the "save" method in the tripInstance bean object. Any error messages are put into the "description field" of the master record form. If everything is fine, then the form is put into "Edit" mode for further editing including adding detail records into the Table below. The new button just puts a new Trip instance into the master record form (and disables the detail table panel) The delete button just deletes the master record. There is no need to "commit" the transaction as it is done automatically, and this differs from Oracle Forms The enter-query button just clears the fields to collect the parameters to search. If all the fields are null, then the QBE will match all records in the database Executing the query will run the "findAll(object)" method of the GORM domain instance. The return result is a List of matching instances. This is not quite scalable as the List needs to be stored in memory for the duration of the session or until the next query is run. This will need to be improved further. If there are any returned records, then the master form will display the first record and put it in "Edit" mode Exiting the Query mode will return the form to the New mode The previous and next buttons will update the master record form and the container of the detail table panel, thus keeping both screens in synchrony. The picture on the left shows the data entry screen with the detail records for the current master record. Future Direction To improve on this, we will need to componentize the whole form so that developers do not need to copy and paste the above template code and modify it for each form. Furthermore the "container" object above should be changeable to allow for other types of containers to be used but they should not be data-bound and leave the data-binding to the GORM objects and layer. Another suggestion is to create a Container component which is manipulated by the master table form buttons (add, save, delete, enter query, execute query, previous record, next record) and it then controls the master table entry Form. Finally, as mentioned in the Petter Holmström article, we are not really using any feature of Grails other than the GORM, and so, this entire example can be build using just Groovy, GORM and Vaadin.

One of the design principles of any enterprise application which I found difficult to make up my mind about is Anemic domain models + Service Objects Vs. Fully featured domain objects. Most of my business application layer consists of many Service Objects (DAOs, Session Beans, BOs, Delegates, Facades etc) AND many POJO domain objects. Here the domain objects are nothing but data holders. There is no business logic in it. Arguably, this is an application of "separation of concerns", where business and/or data access logic is separated from data holders (in other words, Transfer Objects or Value Objects). In my opinion, this also improves the testability of the code. Whereas, there is a counter argument from another side (mostly the proponents of Domain- Driven Development (DDD)) that separating domain objects from its operations is nothing but going back to procedural style of programming. I don't know if I necessarily agree with that argument. Frameworks like Hibernate (even JPA) allows us to embed custom SQL's inside the domain model. In my mind that is a 'mixing' of concerns. Also, imagine a method called sell() inside a 'Book' object. Does a book know how to sell it? Should it know? Also, Book has an existence without a sell() functionality. In cases like this, I prefer the business logic to be separated in to respective Service Classes which results in methods like BookServiceImpl.sell(book) and BookServiceImpl.calculatePrice(book) rather than Book.sell() and Book.calculatePrice(). This is not to totally dismiss the other argument. If we are developing software for a rapidly changing business domain, from a maintainability perspective, DDD approach may sound attractive. For example, when the way company sell books change , the place it requires the code change is most likely the Book.sell() method; where as, if we are to change the service method, it might affect various other sub-systems in which the service methods are re-used. But when Book object requires another domain object (e.g: 'CreditCard' object) to do its selling, things become complicated. Yes, we can inject CreditCard object into Book object, but effectively we are introducing a level of coupling and reducing testability.

It's amazing how the JBoss Team put together an easy way to do JMS Clustering, out of the box!!. I'll start with an easy example, creating a Queue named "MyClusteredQueue". In this example I'm using JBoss AS 5.1. and two computers connected on the same network, with these IP's: - Computer A: 192.168.0.143 - Computer B: 192.168.0.210 So, here are the steps: 1) Install the JBoss on both computers. We are going to use the "all" configuration for both computers. 2) We create our Queue on both servers. Go to $JBOSS_HOME/server/all/deploy/messaging/ and edit the destinations-service.xml file. Add the MyClusteredQueue before the last server tag. It looks like this: jboss.messaging:service=ServerPeer jboss.messaging:service=PostOffice true This is how you add a Queue to the JBoss, and the people how are familiar with this, the only new thing is to add the attribute "Clustered". This step must be set on both computers. At the end of the article you can find the files. 3) Write the MDB to consume the messages, and deploy it on the two computers. (I'm using an EJB 3 - MDB style). import java.net.InetAddress; import javax.ejb.ActivationConfigProperty; import javax.ejb.MessageDriven; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.ObjectMessage; import org.apache.log4j.Logger; /** * @author felipeg * */ @MessageDriven(activationConfig = { @ActivationConfigProperty(propertyName="destinationType", propertyValue="javax.jms.Queue"), @ActivationConfigProperty(propertyName="destination", propertyValue="queue/MyClusteredQueue") }) public class JMSClusterClientHandler implements MessageListener { Logger log = Logger.getLogger(JMSClusterClientHandler.class); @Override public void onMessage(Message message) { try{ if (message instanceof ObjectMessage) { InetAddress addr = InetAddress.getLocalHost(); log.info("########## Processing Host: " + addr.getHostName() + " ##########" ); ObjectMessage objMessage = (ObjectMessage) message; Object obj = objMessage.getObject(); log.info("Object received:" + obj.toString()); } } catch (Exception e) { e.printStackTrace(); } } } 4) Start the jboss with the following options: Computer A: $ cd $JBOSS_HOME/bin $ ./run.sh -c all -b 192.168.0.143 -Djboss.messaging.ServerPeerID=1 Computer B: $ cd $JBOSS_HOME/bin $ ./run.sh -c all -b 192.168.0.210 -Djboss.messaging.ServerPeerID=2 It is necesary to give an ID to each server and this is accomplished with this directive: -Djboss.messaging.ServerPeerID When you start the jboss on computer A, you should see the logs (server.log) telling you that there is one node ready and listening, and once you start the jboss on computer B, on the log will appear the two nodes, the two IP's ready to consume messages. 5) Now it's time to send a Message to the Queue. To accomplish this it's necessary to change the connection factory to "ClusteredConnectionFactory" (JMSDispatcher.java - See the code below). Also on the jndi.properties (if you are using the default InitialContext) file it's necessary to add the two computers ip's separated by comma to the java.naming.provider.url property. (In my case a create a Properties variable and I set all the necessary properties, JMSDispatcher.java - see the code below). java.naming.provider.url=192.168.0.143:1099,192.168.0.210:1099 The client that I wrote is a web application, that consist in one index.jsp page, which contains a form that prompts you for the name of the queue, the type of messaging (Queue or Topic), the server ip and port, how many times it will send the message and the actual message to be sent; also the web application has a Servlet (JMSClusteredClient.java - see code below) that receives the postback and helper class (JMSDispatcher.java - see code below) that sends the message to the jboss servers. You can to deploy it in any computer. In my case I deployed it on the Computer A. And you can access it through this URL: http://192.168.0.143:8080/JMSWeb/ (just modify the IP where the client war was deployed). If you notice (on the index.jsp - code below) I've already put some default values that reflects the name of the Queue, and the IP's of my two computers. Now, If you increment the number of times that the message will be sent (maybe a 10) and fill out the message box, and click "Send" you should see on the two servers some of the messages being consumed by the MDB. Here are the Files to create the client: index.jsp JMS Clustered - Test Client Server: QueueTopic Times:Message: Servlet: JMSClusteredClient.java public class JMSClusteredClient extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response) */ protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); String topicqueue = request.getParameter("topicqueue"); String message = request.getParameter("message"); String server = request.getParameter("server"); String messageType = request.getParameter("messageType"); String times = request.getParameter("times"); int intTimes = Integer.parseInt(times); JMSDispatcher dispatcher = new JMSDispatcher(); dispatcher.setTopicQueueName(topicqueue); dispatcher.setServer(server); dispatcher.setMessageType(messageType); try { for(int count =1; count <= intTimes;count++){ dispatcher.sendMessage( count + " of " + times + " " + message); } out.println("Message [" + message + "] sent successfully to [" + topic + "] to the [" + server + "] server " + times + " times."); } catch (JMSException e) { e.printStackTrace(); out.println("Error:" + e.getMessage()); } catch (NamingException e) { out.println("Error:" + e.getMessage()); e.printStackTrace(); } finally{ out.close(); } } } A utility to send the messages: JMSDispatcher.java public class JMSDispatcher { /** * */ private static final long serialVersionUID = 7105145023422143880L; private static Logger log = Logger.getLogger(JMSDispatcher.class); private final String CONNECTION_FACTORY_CLUSTERED = "ClusteredConnectionFactory"; private final String CONNECTION_FACTORY = "ConnectionFactory"; private final String TOPIC = "TOPIC"; private final String QUEUE = "QUEUE"; private String topicQueueName; private String server; private String messageType; public void setTopicQueueName(String value){ this.topicQueueName = value; } public void setServer(String value){ this.server = value; } public void setMessageType(String value){ this.messageType = value; } public void sendMessage(Object objectMessage) throws JMSException, NamingException{ log.debug("##### Setting up a Queue/Topic Message: #####"); if (TOPIC.equals(messageType)){ sendTopicMessage(objectMessage); } else if (QUEUE.equals(messageType)){ sendQueueMessage(objectMessage); } log.debug("##### Publishing Message: Done #####"); } private void sendQueueMessage(Object objectMessage) throws JMSException, NamingException{ try{ InitialContext initialContext = getInitialContext(); QueueConnectionFactory qcf = (QueueConnectionFactory) initialContext.lookup(CONNECTION_FACTORY_CLUSTERED); QueueConnection queueConn = qcf.createQueueConnection(); Queue queue = (Queue) initialContext.lookup(topicQueueName); QueueSession queueSession = queueConn.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); queueConn.start(); QueueSender send = queueSession.createSender(queue); ObjectMessage om = queueSession.createObjectMessage((Serializable)objectMessage); setMessageProperties(om); log.debug("##### Publishing Message to a Queue: " + queueName + "#####"); send.send(om); send.close(); queueConn.stop(); queueSession.close(); queueConn.close(); }catch(MessageFormatException ex){ log.error("##### The MESSAGE is not Serializable ####"); throw ex; }catch(MessageNotWriteableException ex){ log.error("##### The MESSAGE is not Readable ####"); throw ex; }catch(JMSException ex){ log.error("##### JMS provider fails to set the object due to some internal error. ####"); throw ex; } } private void sendTopicMessage(Object objectMessage) throws JMSException, NamingException{ try{ InitialContext initialContext = getInitialContext(); TopicConnectionFactory tcf = (TopicConnectionFactory)initialContext.lookup(CONNECTION_FACTORY_CLUSTERED); TopicConnection topicConn = tcf.createTopicConnection(); Topic topic = (Topic) initialContext.lookup(topicQueueName); TopicSession topicSession = topicConn.createTopicSession(false,TopicSession.AUTO_ACKNOWLEDGE); topicConn.start(); TopicPublisher send = topicSession.createPublisher(topic); ObjectMessage om = topicSession.createObjectMessage(); om.setObject((Serializable)objectMessage); setMessageProperties(om); log.debug("##### Publishing Message to a Topic: " + topicName + "#####"); send.publish(om); send.close(); topicConn.stop(); topicSession.close(); topicConn.close(); }catch(MessageFormatException ex){ log.error("##### The MESSAGE is not Serializable ####"); throw ex; }catch(MessageNotWriteableException ex){ log.error("##### The MESSAGE is not Readable ####"); throw ex; }catch(JMSException ex){ log.error("##### JMS provider fails to set the object due to some internal error. ####"); throw ex; } } private InitialContext getInitialContext() throws NamingException{ Properties jboss = new Properties(); jboss.put("java.naming.factory.initial", "org.jnp.interfaces.NamingContextFactory"); jboss.put("java.naming.factory.url.pkgs", "org.jboss.naming:org.jnp.interfaces"); jboss.put("java.naming.provider.url", server); return new InitialContext(jboss); } } And the web.xml JMSWeb index.jsp JMSClusteredClient JMSClusteredClient com.blogspot.felipeg48.jms.web.JMSClusteredClient JMSClusteredClient /JMSClusteredClient Happy Clustering!!

HTML5 is really hot all over the web right now so I figured I would drop some HTML5 knowledge on y'all. I have worked with Flash and Flex consistently for the last few years so I can easily drop and manipulate graphics in it, but I haven't done much with HTML5. This lead me to try and challenge myself to recreate something I built in Flash in HTML5. That is what we are going to look at and learn to build in this tutorial. A few things should be mentioned. First IE simply doesn't implement the tag which means it won't work in IE, Google has released Explorer Canvas which fixes this to some extent. I, however, didn't worry about adding that to this tutorial because this post is about creating the content. Also, there are some small things that don't work in other browsers. Finally, Mobile Safari (iPhone, iPod Touch, and iPad) doesn't implement text rendering correctly. To get things rolling we'll first put some simple html down. This includes the tag which is what we're using for this tutorial. The only other element we are going to use is an input button to spin our wheel. I also added a little bit of inline style to place the button. The next thing we are going to do is begin drawing some stuff on to our canvas. This is going to be done in JavaScript in a function I named drawRouletteWheel. The basics of drawing on the in 2D at least involve grabbing a drawing context and then drawing onto it. Sounds complicated doesn't it. Let's look at a little bit of code. var colors = ["#B8D430", "#3AB745", "#029990", "#3501CB", "#2E2C75", "#673A7E", "#CC0071", "#F80120", "#F35B20", "#FB9A00", "#FFCC00", "#FEF200"]; var startAngle = 0; var arc = Math.PI / 6; var ctx; function drawRouletteWheel() { var canvas = document.getElementById("canvas"); if (canvas.getContext) { var outsideRadius = 200; var insideRadius = 125; ctx = canvas.getContext("2d"); ctx.clearRect(0,0,500,500); ctx.strokeStyle = "black"; ctx.lineWidth = 2; for(var i = 0; i < 12; i++) { var angle = startAngle + i * arc; ctx.fillStyle = colors[i]; ctx.beginPath(); ctx.arc(250, 250, outsideRadius, angle, angle + arc, false); ctx.arc(250, 250, insideRadius, angle + arc, angle, true); ctx.stroke(); ctx.fill(); } } } Okay, looking at the start of the function we grab a reference to our canvas object by id - nothing new here. Then we check to make sure the browser supports grabbing a drawing context, this is important to make sure we don't throw errors in browsers that don't support the features. Then we set a couple of variables for the inner and outer radius of our wheel. Now, we get into the meat. The first thing we do is grab a 2D drawing context by calling getContext. From here we clear the canvas, so we have a blank slate to draw onto. Then we set the stroke color and width which in this case is "black" and 2. The next part takes a little bit of explaining, we are going to loop through 12 sections (the number of sides we are going to draw). For each section we determine the angle of where each section is going to start. The startAngle is a global variable in which we are going to use to animate the wheel, for now, it is set to 0. The following line sets the fill color by pulling a value from the global colors array. Drawing begins after that with starting a path drawing two arcs, using the arc(x, y, radius, startAngle, endAngle, anticlockwise) function. We then tell the context to stroke the path and fill the path, these will use the previously set parameters. Now, we are going to add the restaurant text to our drawing code. Also, to finish off the drawing function we'll add the nice little arrow at the top. The text drawing is done using the fillText(text, x, y [, maxWidth ]) function. Let's take a look at the updated code. var restaraunts = ["Wendy's", "McDonalds", "Chick-fil-a", "Five Guys", "Gold Star", "La Mexicana", "Chipotle", "Tazza Mia", "Panera", "Just Crepes", "Arby's", "Indian"]; function drawRouletteWheel() { var canvas = document.getElementById("canvas"); if (canvas.getContext) { var outsideRadius = 200; var textRadius = 160; var insideRadius = 125; ctx = canvas.getContext("2d"); ctx.clearRect(0,0,500,500); ctx.strokeStyle = "black"; ctx.lineWidth = 2; ctx.font = 'bold 12px Helvetica, Arial'; for(var i = 0; i < 12; i++) { var angle = startAngle + i * arc; ctx.fillStyle = colors[i]; ctx.beginPath(); ctx.arc(250, 250, outsideRadius, angle, angle + arc, false); ctx.arc(250, 250, insideRadius, angle + arc, angle, true); ctx.stroke(); ctx.fill(); ctx.save(); ctx.shadowOffsetX = -1; ctx.shadowOffsetY = -1; ctx.shadowBlur = 0; ctx.shadowColor = "rgb(220,220,220)"; ctx.fillStyle = "black"; ctx.translate(250 + Math.cos(angle + arc / 2) * textRadius, 250 + Math.sin(angle + arc / 2) * textRadius); ctx.rotate(angle + arc / 2 + Math.PI / 2); var text = restaraunts[i]; ctx.fillText(text, -ctx.measureText(text).width / 2, 0); ctx.restore(); } //Arrow ctx.fillStyle = "black"; ctx.beginPath(); ctx.moveTo(250 - 4, 250 - (outsideRadius + 5)); ctx.lineTo(250 + 4, 250 - (outsideRadius + 5)); ctx.lineTo(250 + 4, 250 - (outsideRadius - 5)); ctx.lineTo(250 + 9, 250 - (outsideRadius - 5)); ctx.lineTo(250 + 0, 250 - (outsideRadius - 13)); ctx.lineTo(250 - 9, 250 - (outsideRadius - 5)); ctx.lineTo(250 - 4, 250 - (outsideRadius - 5)); ctx.lineTo(250 - 4, 250 - (outsideRadius + 5)); ctx.fill(); } } Looking at the new text drawing we start by saving the current context state - this is going to allow us to rotate and translate the text without affecting everything else. We then set some shadow stuff, which will put a drop shadow on the text. Translating and rotating the text is tackled next, we first translate the text to the correct placement on the wheel and then rotate it. Drawing the text follows this but with the added effect of centering the text by measuring it and dividing that by 2 to offset it. You'll notice we grab the restaurant name from a global array. Lastly we restore to our initial state we saved to, this makes sure the transformations do not affect later drawing. The arrow is even easier to explain, we just move to one corner and draw lines to create the shape and fill it with black. Below I have the complete code for this demo. I'll explain the spinning and animating code right after. var colors = ["#B8D430", "#3AB745", "#029990", "#3501CB", "#2E2C75", "#673A7E", "#CC0071", "#F80120", "#F35B20", "#FB9A00", "#FFCC00", "#FEF200"]; var restaraunts = ["Wendy's", "McDonalds", "Chick-fil-a", "Five Guys", "Gold Star", "La Mexicana", "Chipotle", "Tazza Mia", "Panera", "Just Crepes", "Arby's", "Indian"]; var startAngle = 0; var arc = Math.PI / 6; var spinTimeout = null; var spinArcStart = 10; var spinTime = 0; var spinTimeTotal = 0; var ctx; function drawRouletteWheel() { var canvas = document.getElementById("canvas"); if (canvas.getContext) { var outsideRadius = 200; var textRadius = 160; var insideRadius = 125; ctx = canvas.getContext("2d"); ctx.clearRect(0,0,500,500); ctx.strokeStyle = "black"; ctx.lineWidth = 2; ctx.font = 'bold 12px Helvetica, Arial'; for(var i = 0; i < 12; i++) { var angle = startAngle + i * arc; ctx.fillStyle = colors[i]; ctx.beginPath(); ctx.arc(250, 250, outsideRadius, angle, angle + arc, false); ctx.arc(250, 250, insideRadius, angle + arc, angle, true); ctx.stroke(); ctx.fill(); ctx.save(); ctx.shadowOffsetX = -1; ctx.shadowOffsetY = -1; ctx.shadowBlur = 0; ctx.shadowColor = "rgb(220,220,220)"; ctx.fillStyle = "black"; ctx.translate(250 + Math.cos(angle + arc / 2) * textRadius, 250 + Math.sin(angle + arc / 2) * textRadius); ctx.rotate(angle + arc / 2 + Math.PI / 2); var text = restaraunts[i]; ctx.fillText(text, -ctx.measureText(text).width / 2, 0); ctx.restore(); } //Arrow ctx.fillStyle = "black"; ctx.beginPath(); ctx.moveTo(250 - 4, 250 - (outsideRadius + 5)); ctx.lineTo(250 + 4, 250 - (outsideRadius + 5)); ctx.lineTo(250 + 4, 250 - (outsideRadius - 5)); ctx.lineTo(250 + 9, 250 - (outsideRadius - 5)); ctx.lineTo(250 + 0, 250 - (outsideRadius - 13)); ctx.lineTo(250 - 9, 250 - (outsideRadius - 5)); ctx.lineTo(250 - 4, 250 - (outsideRadius - 5)); ctx.lineTo(250 - 4, 250 - (outsideRadius + 5)); ctx.fill(); } } function spin() { spinAngleStart = Math.random() * 10 + 10; spinTime = 0; spinTimeTotal = Math.random() * 3 + 4 * 1000; rotateWheel(); } function rotateWheel() { spinTime += 30; if(spinTime >= spinTimeTotal) { stopRotateWheel(); return; } var spinAngle = spinAngleStart - easeOut(spinTime, 0, spinAngleStart, spinTimeTotal); startAngle += (spinAngle * Math.PI / 180); drawRouletteWheel(); spinTimeout = setTimeout('rotateWheel()', 30); } function stopRotateWheel() { clearTimeout(spinTimeout); var degrees = startAngle * 180 / Math.PI + 90; var arcd = arc * 180 / Math.PI; var index = Math.floor((360 - degrees % 360) / arcd); ctx.save(); ctx.font = 'bold 30px Helvetica, Arial'; var text = restaraunts[index] ctx.fillText(text, 250 - ctx.measureText(text).width / 2, 250 + 10); ctx.restore(); } function easeOut(t, b, c, d) { var ts = (t/=d)*t; var tc = ts*t; return b+c*(tc + -3*ts + 3*t); } drawRouletteWheel(); It's a lot to take in but we'll take it slow. At the bottom of the code you'll see we call drawRouletteWheel, this is too draw the initial wheel when the page loads. We have to update the input button we put on the screen to now call our spin function, which handles spinning the wheel, of course. The updated input follows. Taking a look at the spin function we set a couple global variables that decide how fast we are going to spin and how long we are going to spin. These have a little bit of randomness in them to make things more interesting. Lastly, we call rotateWheel. The rotateWheel function updates the amount of time we have been spinning, checks to see if we should stop, updates spinning speed, draws the wheel, and then calls itself in 30 milliseconds. After checking the time we change the spinning angle, startAngle, this is done using an easing function to slow down the spinning. Then we call our drawing function and use setTimeout and keeps a reference to call our rotate again. The last function we need look at is stopping the wheel, stopRotateWheel. This starts with clearing the timeout which will stop the code from rotating the wheel. Then we use some math to figure out what restaurant is at the top. Finally, we draw the large name of the of the selected restaurant in the middle of the wheel. Well, that's pretty much a wrap on this post. I really like how HTML5 and the canvas tag are coming along. Although it's not quite ready for primetime production work yet. I look forward to the next couple years of web development. If you have any questions on the tutorial or just want to bash on my coding skills feel free to drop a comment.

Lazy initialization is a common procedure in programming, especially in an environment like PHP applications where during a specific HTTP request it's practically sure that there are resources which won't be used at all, and that, if eager loaded, would be simply discarded without being referenced again. The Lazy Loading pattern for stateful objects is a transparent solution for loading entity objects on demand, when they are referenced troughout client code. Its typical usage is in the internals of an ORM or in another kind of Data Mapper. Lazy Loading is not a mapper-specific pattern, but in the environment of enterprise patterns this is the best example of its application. Intent In general, the object graph managed by a Data Mapper can be large at will, and loading the entire graph to satisfy a request which usually involves only a small subset of it is a waste. This is the case when using many-to-many bidirectional relationships, as it is the case with the Unix users and groups model. For example, loading an User will bring back also his referenced groups, which in turn will reference their contained users and so on... In general, it is not possible to always break the relationships in one direction to simplify the model. In this case, full loading is not a waste: it's not feasible unless you have gigabytes of ram to allocate per every request. Another use case for lazy loading of domain model entities is in arbitrary computation to perform when there is no knowledge a priori of the extent of the object graph that will be reached by the method calls (or field access). For example, we may want to do a statistical analysis of the userw reachable from a particular starting point through groups relationships, and stop the research when we have reached a predetermined number of users. In this kind of computation, we cannot know for sure how much JOINs we will have to perform as this is an example of a query which falls out of the scope of SQL. Implementation Lazy Loading is generally implemented with a Proxy pattern, where a fake entity is substituted to the real objects at the boundary of the object graph. This fake entities do not load relationships and fields when they are first inserted in the graph. The Proxy pattern implementation used here is the ghost variant, where the object is essentially a proxy for itself, since the field are loaded and stored in it on the first access. The ghost has only its identifier fields loaded by default, and it is inserted in the Identity Map anyway. The PHP implementation of Lazy Loading mechanism in ORMs has to respect some caveats to work. For starters, the Proxy object substituted for the real one has to conform to the same interface of the original class. This is accomplished via subclassing since there is usually no explicit interface (defined with the interface keyword) for domain objects. This subclass may be generated previous to its usage or at runtime, when it comes the time to insert a proxy in the graph. The methods of the entity, such as getters, setters, or logic-related ones are overridden, and their new implementations call a load() method before delegating to the parent method. The load() private method uses a reference to the Entity Manager or to some internal component of the Orm to load the fields of the object itself, and its relationships. Note that this referenced objects can be proxies in turn. Of course, the load() method has a boolean guard that makes it perform real execution of queries only one time, since if the object has already been loaded its behavior returns to be the original class's one. Lazy Loading can be used also for public properties via __get() and __set() overriding, but it is maybe too much transparent as accessing a public property may cause a query to the database. PHP magic methods are often abused. Performance Lazy Loading may cause performance problems when used extensively. The main issues is that it promotes many small queries to load objects one at the time, instead of a big JOIN which can load the whole object graph subset needed, avoiding the overhead of all the unnecessary queries and a chatty communication. Even if the database is high-performance or not relational or whatever, if it resides on another machine communication over the network will experience longer latency and it is best performed in batches. Parts of the graph to eager load via joins (instead of lazy load) can be specified while querying via the language of choice (HQL, JQL, Linq, DQL) or via programmatic interface (Criteria object). This part of the relational information crosses the boundary of the ORM to reach its client code, but it is mandatory to optimize the generated queries to an acceptable level. One solution is to encapsulate it in Repository implementations, that provide a domain-specific interface and hide all the queries in the object-related language of the ORM. Lazy Loading is complex, and it is perfect for outsourcing to a library like an Orm. Be aware of the issues it causes on performance and you will be able to take advantage of it without causing strain on your database. Example The code sample for this ORM pattern is taken from Doctrine 2, where I contributed part of the code related to lazy loading one-to-one and many-to-one relationships. The class presented here is the ProxyFactory, which generates a proxy object for a particular entity and, if needed, the source code for the proxy class. I have inserted some extension to the docblock comments. * @author Giorgio Sironi * @since 2.0 */ class ProxyFactory { /** The EntityManager this factory is bound to. */ private $_em; /** Whether to automatically (re)generate proxy classes. */ private $_autoGenerate; /** The namespace that contains all proxy classes. */ private $_proxyNamespace; /** The directory that contains all proxy classes. */ private $_proxyDir; /** * Initializes a new instance of the ProxyFactory class that is * connected to the given EntityManager. * * @param EntityManager $em The EntityManager the new factory works for. * @param string $proxyDir The directory to use for the proxy classes. It must exist. * @param string $proxyNs The namespace to use for the proxy classes. * @param boolean $autoGenerate Whether to automatically generate proxy classes. */ public function __construct(EntityManager $em, $proxyDir, $proxyNs, $autoGenerate = false) { if ( ! $proxyDir) { throw ProxyException::proxyDirectoryRequired(); } if ( ! $proxyNs) { throw ProxyException::proxyNamespaceRequired(); } $this->_em = $em; $this->_proxyDir = $proxyDir; $this->_autoGenerate = $autoGenerate; $this->_proxyNamespace = $proxyNs; } /** * Gets a reference proxy instance for the entity of the given type and identified by * the given identifier. * Generalle this method will reuse the source code it has already generated, even in * other HTTP requests since the source file are saved in a configurable folder. * This is the only public method the other parts of the ORM will generally use. * * @param string $className * @param mixed $identifier * @return object */ public function getProxy($className, $identifier) { $proxyClassName = str_replace('\\', '', $className) . 'Proxy'; $fqn = $this->_proxyNamespace . '\\' . $proxyClassName; if ($this->_autoGenerate && ! class_exists($fqn, false)) { $fileName = $this->_proxyDir . DIRECTORY_SEPARATOR . $proxyClassName . '.php'; $this->_generateProxyClass($this->_em->getClassMetadata($className), $proxyClassName, $fileName, self::$_proxyClassTemplate); require $fileName; } if ( ! $this->_em->getMetadataFactory()->hasMetadataFor($fqn)) { $this->_em->getMetadataFactory()->setMetadataFor($fqn, $this->_em->getClassMetadata($className)); } $entityPersister = $this->_em->getUnitOfWork()->getEntityPersister($className); return new $fqn($entityPersister, $identifier); } /** * Generates proxy classes for all given classes. * Used for pre-generation from command line, in case PHP on the hosting service * has not the rights to create new files in the proxies folder. * * @param array $classes The classes (ClassMetadata instances) for which to generate proxies. * @param string $toDir The target directory of the proxy classes. If not specified, the * directory configured on the Configuration of the EntityManager used * by this factory is used. */ public function generateProxyClasses(array $classes, $toDir = null) { $proxyDir = $toDir ?: $this->_proxyDir; $proxyDir = rtrim($proxyDir, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR; foreach ($classes as $class) { $proxyClassName = str_replace('\\', '', $class->name) . 'Proxy'; $proxyFileName = $proxyDir . $proxyClassName . '.php'; $this->_generateProxyClass($class, $proxyClassName, $proxyFileName, self::$_proxyClassTemplate); } } /** * Generates a proxy class file. * Substitutes certain parameters like class name and methods in a template * kept at the end of this file. The class source code is saved in a file in the directory specified. * Testing this method is usually not a problem since the directory is easily configurable. * * @param $class * @param $originalClassName * @param $proxyClassName * @param $file The path of the file to write to. */ private function _generateProxyClass($class, $proxyClassName, $fileName, $file) { $methods = $this->_generateMethods($class); $sleepImpl = $this->_generateSleep($class); $placeholders = array( '', '', '', '', '' ); if(substr($class->name, 0, 1) == "\\") { $className = substr($class->name, 1); } else { $className = $class->name; } $replacements = array( $this->_proxyNamespace, $proxyClassName, $className, $methods, $sleepImpl ); $file = str_replace($placeholders, $replacements, $file); file_put_contents($fileName, $file); } /** * Generates the methods of a proxy class. * All methods are overridden to call _load() before execution. * * @param ClassMetadata $class * @return string The code of the generated methods. */ private function _generateMethods(ClassMetadata $class) { $methods = ''; foreach ($class->reflClass->getMethods() as $method) { /* @var $method ReflectionMethod */ if ($method->isConstructor() || strtolower($method->getName()) == "__sleep") { continue; } if ($method->isPublic() && ! $method->isFinal() && ! $method->isStatic()) { $methods .= PHP_EOL . ' public function '; if ($method->returnsReference()) { $methods .= '&'; } $methods .= $method->getName() . '('; $firstParam = true; $parameterString = $argumentString = ''; foreach ($method->getParameters() as $param) { if ($firstParam) { $firstParam = false; } else { $parameterString .= ', '; $argumentString .= ', '; } // We need to pick the type hint class too if (($paramClass = $param->getClass()) !== null) { $parameterString .= '\\' . $paramClass->getName() . ' '; } else if ($param->isArray()) { $parameterString .= 'array '; } if ($param->isPassedByReference()) { $parameterString .= '&'; } $parameterString .= '$' . $param->getName(); $argumentString .= '$' . $param->getName(); if ($param->isDefaultValueAvailable()) { $parameterString .= ' = ' . var_export($param->getDefaultValue(), true); } } $methods .= $parameterString . ')'; $methods .= PHP_EOL . ' {' . PHP_EOL; $methods .= ' $this->_load();' . PHP_EOL; $methods .= ' return parent::' . $method->getName() . '(' . $argumentString . ');'; $methods .= PHP_EOL . ' }' . PHP_EOL; } } return $methods; } /** * Generates the code for the __sleep method for a proxy class. * The __sleep() method is used in case of serialization, which should * not include service objects referenced by proxies like the Entity Manager. * * @param $class * @return string */ private function _generateSleep(ClassMetadata $class) { $sleepImpl = ''; if ($class->reflClass->hasMethod('__sleep')) { $sleepImpl .= 'return parent::__sleep();'; } else { $sleepImpl .= 'return array('; $first = true; foreach ($class->getReflectionProperties() as $name => $prop) { if ($first) { $first = false; } else { $sleepImpl .= ', '; } $sleepImpl .= "'" . $name . "'"; } $sleepImpl .= ');'; } return $sleepImpl; } /** Proxy class code template */ private static $_proxyClassTemplate = '; /** * THIS CLASS WAS GENERATED BY THE DOCTRINE ORM. DO NOT EDIT THIS FILE. */ class extends \ implements \Doctrine\ORM\Proxy\Proxy { private $_entityPersister; private $_identifier; public $__isInitialized__ = false; public function __construct($entityPersister, $identifier) { $this->_entityPersister = $entityPersister; $this->_identifier = $identifier; } private function _load() { if (!$this->__isInitialized__ && $this->_entityPersister) { $this->__isInitialized__ = true; if ($this->_entityPersister->load($this->_identifier, $this) === null) { throw new \Doctrine\ORM\EntityNotFoundException(); } unset($this->_entityPersister); unset($this->_identifier); } } public function __sleep() { if (!$this->__isInitialized__) { throw new \RuntimeException("Not fully loaded proxy can not be serialized."); } } }'; }

Steven Yi (pictured right) is a programmer and composer living in Rochester, NY. He studied music composition in college and became a programmer afterwards. He started off as a Flash and server side developer (which he did for about 7 years), and has spent the past few years at his current company doing mobile development with J2ME, Android, and iPhone, as well as server-side development with Spring, Hibernate, etc. He started learning and using Java and Swing for personal work in 2000 and has been using it since then for the development of blue, the focus of the interview that follows below. In the interview, Steven talks about the "blue" music composer, how it works, and how the NetBeans Platform and Python form the basis of this cool open-sourced Java music composer. What's "blue"? blue is a music composition environment I started in the fall of 2000. It was actually my very first Java program! At the time, I had started using the music software Csound (http://www.csounds.com) to compose, but found it slow to work with when it came to accomplishing what I was interested in musically. I had the idea to create a simple program that would have a timeline and the ability to scale musical score material in time. Fast forward many years later: in trying to solve other musical problems, and responding to feedback from the community of users, I've expanded blue's features a great deal. It now includes things like a mixer and effects system, a GUI builder tool for creating synthesizer interfaces, embedded Jython processing of musical scripts, and more. It's been quite satisfying to create a tool that can express my musical interests and to find a community of users who have found value in this program for their own musical work. Some screenshots: The Orchestra manager shows a BlueSynthBuilder instrument being edited. The "Reson 6" instrument is shown in edit mode. The BSB Object Properties panel shows the properties for the selected knob: The Score timeline shows a project using multiple parameter automations. The values automated include things like volume, panning, and a time pointer for a phase-vocoder instrument. All BlueSynthBuilder instruments, Effects, and the Mixer volume sliders can be automated: The Score timeline showing the author's composition "Reminiscences". The timeline shows multiple Python SoundObjects used. The SoundObject Editor shows the editor for the selected SoundObject in the timeline. The SoundObject Properties panel shows different properties for the selected SoundObject: The Score timeline showing a Tracker SoundObject being used. The timeline is configured to snap at every 4 beats and the time bar has been configured to show in numbers rather than time: The Score timeline showing a PianoRoll SoundObject being used. The PianoRoll is unique in that it is microtonal, meaning it can adapt the number of steps per "octave", depending on the values configured from a tuning file. In this screenshot, the scale loaded was a Bohlen-Pierce scale, which has 13-tones per tritave (octave and a half): The blue Mixer is shown docked into the bottom bar and in an open state. The interfaces for user-created Chorus and Reverb effects are shown. The interfaces were created using the same GUI builder tool that is found in the BlueSynthBuilder instrument: It's got a very special appearance. How did that come about? blue's custom look and feel started off one day when I was using my Palm PDA. I remember thinking that I enjoyed the look of the device with the backlight on, and so I wanted to recreate that kind of look for my program. Later, I modified the color scheme to tone it down in some ways, but I also introduced more colors than white and cyan to highlight secondary and tertiary features. Maybe now it is now more like Tron than it is like Palm. :) Overall, I enjoy the darker look of the application when I'm working on music. I tend to work on music when I have free time, and that is usually only late at night—I've found having a darker screen has been easier on my eyes. Also, if anyone was wondering, yes, blue is my favorite color. The blue look and feel is encapsulated in a module named "blue-plaf" and is available in the "blue" Mercurial repository (http://bluemusic.hg.sourceforge.net/hgweb/bluemusic/blue). The look and feel is quite hacked up (redoing it properly has been another item on my todo list), but it can be dropped into another application and it should work, as shown below with the CRUD Sample (which can be created from a tutorial found here): Can you explain how blue's timeline works? blue has a concept of SoundLayers and SoundObjects. SoundObjects are objects that primarily produce notes and have a start and duration. There are many different types of SoundObjects in blue and each has an editor (viewed in the SoundObject Editor TopComponent when a SoundObject is selected), and a BarRenderer, which is used to draw the content area of the bar on the timeline. A PolyObject is a special SoundObject. It consists of SoundLayers, which contain SoundObjects. The root timeline is itself just a PolyObject that you can add as many layers to as you like. You can also group individual SoundObjects into their own PolyObjects, and then use the resulting PolyObjects just like any other SoundObject on the timeline. If you double-click a PolyObject, the timeline is then reset with the timeline of the PolyObject you selected. As a result, PolyObjects allow timelines to be embedded within other timelines. If you think about how music is grouped into motives, phrases, sections, and even larger groupings, you can see how PolyObjects might represent these kinds of musical abstractions. For the component design, the ScoreTopComponent starts off with a JSplitPane to split between a SoundLayerListPanel on the left and a JScrollPane on the right. The JScrollPane has a ScoreTimeCanvas (the main timeline) in the main viewPort's view, a panel with the the time bar and tempo editor in the column header, and the corner is used to open up an extra panel to modify properties for the timeline. The JScrollPane has customized JScrollBars used to add the ± buttons that perform zooming on the timeline. There are a number of other features involved that are implemented amongst a number of classes, but the details of how viewPorts are synchronized (among other things) may be a bit too technical to discuss here. For those who are interested, the code can be viewed within the blue.ui.core.score package within the blue-ui-core module. How did blue come to find itself atop the NetBeans Platform? I first started to be interested in NetBeans IDE around the time 4.1 came out, but didn't really get into using it until the release of 5.0. At that time, I had hand-written Swing components for about 4-5 years (I don't really remember when 5.0 was released), and I found Matisse to be quite nice and began using it here and there. I had looked at the NetBeans Platform as an RCP at that time, but found it to be quite a bit to understand. However, I still kept it on my radar. Around the time 6.0 or 6.5 came out, I started to reconsider migrating to the NetBeans Platform once again. By this time, I had moved over to using NetBeans IDE full time for blue development and had been using NetBeans IDE more in general—particularly Java Web development and Ruby on Rails. One of the biggest things I found attractive about NetBeans IDE is its windowing system... and the things I read about in the platform development articles I'd seen online made me curious once again to see what the NetBeans Platform offered. I still felt that there was going to be a big learning curve to learn the NetBeans Platform, but the NetBeans Platform tutorials online were really quite helpful, as were the members of the NetBeans Platform mailing list, and there were also many more books available to help me get started. I think I ultimately spent about 6-8 months migrating blue to using the NetBeans Platform. Granted, it was a busy time in my life and I was working on this only in my spare time, so I think in the end it was a reasonable amount of time. Users have been very positive about the new blue interface and application as a whole, and I think it has been worth spending the time to use the NetBeans Platform. blue's window layout is quite unexpected for a NetBeans Platform application. By the time I had started migrating blue to the NetBeans Platform, the application was already some 7-8 years old. The interface I designed for blue in pure Swing was influenced by my experiences in using Flash, looking at other music composition environments (Digital Audio Workstations and Sequencing Programs), and evaluating the different aspects of working with Csound. Mapping the components from the Swing-based application to the NetBeans Platform was a little tricky in that I couldn't quite get the exact same design of panels as I had in pure Swing. In the end, I tried to think about where most of the components resided physically, and created TopComponents and placed them in the center, left, right, or bottom parts of the main window. I kept some of the dialogs from the old codebase as-is, but I migrated others to be TopComponents so that they could be docked, opened, or dragged out into a dialog as the user wished. In the end, the GUI is different and took a little getting used to after years of using and building the old interface, but I quickly adjusted to the changes and I think there is much greater consistency and usability now. The users have responded very positively to the general polish of the application and to being able to customize their environment. I myself have very much enjoyed being able to dock all of the windows as well as using full-screen mode, especially when I am on my netbook and composing. Excellent! What features of the NetBeans Platform are you using and what do you find to be most useful? Currently, I am using only a very small part of the NetBeans Platform. By the time I started to move my code to the NetBeans Platform, the codebase was already some 7 or 8 years old. I took the approach recommended to me on the mailing list and started off small, focusing primarily on migrating my project to using the Windows System API, the Options API, and a few other utility API's like IO and Dialogs. Having an old codebase, I found that I spent most of my time during migration just reorganizing my UI into TopComponents and working out communications between the components. I also spent time looking at API's that I had developed myself and seeing which ones could be replaced with API's provided by the NetBeans Platform. At this time, the application is still using a number of API's I wrote from the old codebase, but over time I would like to migrate more of the appplication to use the Nodes and Visual Library API's. I think migrating a codebase of this size in phases really worked out well. In the first phase, I was able to take advantage of the Window System API and have a very visible result on the application and gained a lot for usability. Also, a big part of the migration involved moving the codebase from a monolithic source tree and partitioning it into logical modules. I think there really is a great deal of benefit to working with a codebase with modular design, and that too is a very positive result of working with the NetBeans Platform. Please say something about how Jython relates to this application, how you are using it (what the benefits are), and your general opinions on Jython. I have had a Python SoundObject in blue for quite some time—I think since 2002. For me, it is one of the most important tools in blue when it comes to accomplishing what I want musically. With computer music, we have a lot of tools for what I call Common Practice computer music: PianoRolls, Pattern Editors, and Notation Objects. For computer musicians who are interested in Uncommon Practice music, the ability to use a scripting language opens up a number of ways to express musical ideas that cannot be easily conveyed using those other tools. In blue, Jython is primarily used to allow users to write scripts that will generate notes. For myself, I use Python scripts to model orchestral composition, creating Performer and PerformerGroup objects that I write in Python. I also write performance functions, usually per-project, to perform different musical material in different ways. Other users have used Python scripts in exploring things like algorithmic composition and genetic algorithms in their work. A blue project can contain any number of Python objects. The score generated by each Python object is translated and scaled in time by moving and resizing the SoundObject in the timeline. This allows a user who may want to use scripting to create musical material to also take advantage of blue's timeline to organize how the different musical objects will work together. One of the things I most appreciate about Jython (and scripting languages on the JVM in general) is that it is embeddable within a Java application. By packaging and embedding the Jython interpreter within the blue application, users can rest assured that the Python scripts they write can be interpreted anywhere that blue is installed. It's an extra assurance that their musical projects will be long-lasting, but they can still take advantage of a full programming language like Python in their work. Overall, I think that Jython is a fine piece of software and I hope that it will continue to grow and develop for years to come. Is the application open source and are you looking for code contributions and, if so, in which areas? Yes, the application is available under the GPL v2 license, and the source code can be viewed from the Mercurial repository on SourceForge at http://bluemusic.hg.sourceforge.net/hgweb/bluemusic/blue/. I am a strong proponent of open source, especially for creative work. In the same way that we can today look at and study musical works by composers of the past (like Josquin and Bach), I would like to imagine that the work composers and other artists are now creating with computers will also be open and available for study in the future. I believe that using open source software for creative work greatly helps in making musical projects available for the years ahead. I have done most of the development of blue myself, and over the years I've certainly built up a long list of things that I would like to implement. Users have also made wonderful feature requests that I would love to see in the program—but unfortunately, there are only so many hours in the day. It would certainly be nice to have others contributing code! Beyond new features, there are a number of infrastructural things that would be nice to address. The codebase is many years old, and while the application has been refactored multiple times over its lifetime, there are still some areas of the application that could be much more cleanly implemented. Also, in moving over to the NetBeans Platforms, I only really took the first steps. There are a number of components within the application that could probably be better served by migrating to using more of the NetBeans API's. For internal work, things like modifying the timeline to implement zooming to use Graphics2d and transforms, implementing a better waveform renderer for audio files, and further enhancing the instrument GUI builder are all things I'd like to see. I'd also love to get help in migrating all of the tables and trees to using the Nodes API, something that I have not yet had the time to do. It would also be nice to get the manual (currently in HTML and PDF, generated from DocBook) integrated into the application as JavaHelp, but this is another thing that I have had to postpone due to lack of time. For features, some interesting things I'd love to see are a Notation SoundObject, a separate graphical instrument builder using the Visual Library API, and a Sampler instrument. There's also a sound drawing SoundObject, enhancements to existing SoundObjects, and more I'd love to see moving forward. Maybe someone will find these kinds of things interesting and will take a look at blue's code sometime! Thanks Steven and happy music making with blue!

Cucumber is a Behavior-Driven Development tool that lets developers describe their software's behavior in plain text using a business-readable DSL (Domain-Specific Language). Project developers have added a useful adapter for Cucumber which allows users to write step definitions in JavaScript instead of Ruby (described in Joseph Wilk's blog). To use Cucumber, you previously needed to know a slight amount of Ruby, now you can completely forgo using Ruby if you know a little JavaScript. Cucumber supports testing for Java, Ruby, .Net, Flex, Python, web languages, and more. Here are the home page's seven steps for using Cucumber: Describe behaviour in plain text Write a step definition in Ruby (Now you can do this in pure JS!) Run and watch it fail Write code to make the step pass Run again and see the step pass Repeat 2-5 until green like a cuke Repeat 1-6 until the money runs out The new adapter in Cucumber is able to provide JS support for step definitions through TheRubyRacer. This tool allowed Cucumber developers to build the JS adapter by embedding Google's V8 JavaScript interpreter into Ruby. Here is an example of the feature: Feature: Fibonacci In order to calculate super fast fibonacci series As a Javascriptist I want to use Javascript for that @fibonacci Scenario Outline: Series When I ask Javascript to calculate fibonacci up to Then it should give me Examples: | n | series | | 1 | [] | | 2 | [1, 1] | | 3 | [1, 1, 2] | | 4 | [1, 1, 2, 3] | | 6 | [1, 1, 2, 3, 5] | | 9 | [1, 1, 2, 3, 5, 8] | | 100 | [1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89] | And the step definitions in JS: Before(['@fibonacci'], function(){ fibResult = 0; }); When(/^I ask Javascript to calculate fibonacci up to (\d+)$/, function(n){ assertEqual(0, fibResult) fibResult = fibonacciSeries(n); }); Then(/^it should give me (\[.*\])$/, function(expectedResult){ assertEqual(expectedResult, fibResult) }); Cucumber developers have tried to make the JS API and the Ruby API as similar as possible, but the JS API currently doesn't have support for calling step definitions within step definitions with multi-line arguments. It also doesn't support line reporting on step definitions. The JS API also has a different way for loading code into the 'World' to make sure it is in scope within the step definitions. For this kind of folder structure: my_js_project/lib/code_lives_here.js my_js_project/features/support/env.js my_js_project/features/my_feature.feature There would be this code within the features/support/env.js setup file: //Cucumber resolves the files relative to the folder that contains the features folder. World(['lib/code_lives_here.js']) Code inside the code_lives_here.js file would be available in the step definitions.