Announcing the new Swing Tree Table yesterday, Tim Boudreau writes: Usage is incredibly easy - you just provide a standard Swing TreeModel of whatever sort you like, and an additional RowModel that can be queried for the other columns contents, editability and so forth. I found an example from some time ago, by Tim, and have been playing with it to get used to this new development. The result is as follows: To get started, I simply download the latest NetBeans IDE development build from netbeans.org and then attached the platform8/org-netbeans-swing-outline.jar to my Java SE project. For the rest, I wasn't required to do anything with NetBeans, necessarily. I could have attached the JAR to a project in Eclipse or anywhere else. Then I created a JFrame. To work with this Swing tree table, you need to provide the new "org.netbeans.swing.outline.Outline" class with the new "org.netbeans.swing.outline.OutlineModel" which, in turn, is built from a plain old javax.swing.tree.TreeModel, together with the new "org.netbeans.swing.outline.RowModel". Optionally, to change the default rendering, you can use the new "org.netbeans.swing.outline.RenderDataProvider". Let's first create a TreeModel for accessing files on disk. We will receive the root of the file system as a starting point: private static class FileTreeModel implements TreeModel { private File root; public FileTreeModel(File root) { this.root = root; } @Override public void addTreeModelListener(javax.swing.event.TreeModelListener l) { //do nothing } @Override public Object getChild(Object parent, int index) { File f = (File) parent; return f.listFiles()[index]; } @Override public int getChildCount(Object parent) { File f = (File) parent; if (!f.isDirectory()) { return 0; } else { return f.list().length; } } @Override public int getIndexOfChild(Object parent, Object child) { File par = (File) parent; File ch = (File) child; return Arrays.asList(par.listFiles()).indexOf(ch); } @Override public Object getRoot() { return root; } @Override public boolean isLeaf(Object node) { File f = (File) node; return !f.isDirectory(); } @Override public void removeTreeModelListener(javax.swing.event.TreeModelListener l) { //do nothing } @Override public void valueForPathChanged(javax.swing.tree.TreePath path, Object newValue) { //do nothing } } The above could simply be set as a JTree's model and then you'd have a plain old standard JTree. It would work, no problems, it would be a normal JTree. However, it wouldn't be a tree table since you'd only have a tree, without a table. Therefore, let's now add two extra columns, via the new "org.netbeans.swing.outline.RowModel" class, which will enable the creation of a tree table instead of a tree: private class FileRowModel implements RowModel { @Override public Class getColumnClass(int column) { switch (column) { case 0: return Date.class; case 1: return Long.class; default: assert false; } return null; } @Override public int getColumnCount() { return 2; } @Override public String getColumnName(int column) { return column == 0 ? "Date" : "Size"; } @Override public Object getValueFor(Object node, int column) { File f = (File) node; switch (column) { case 0: return new Date(f.lastModified()); case 1: return new Long(f.length()); default: assert false; } return null; } @Override public boolean isCellEditable(Object node, int column) { return false; } @Override public void setValueFor(Object node, int column, Object value) { //do nothing for now } } Now, after dragging-and-dropping an Outline object onto your JFrame (which is possible after adding the beans from the JAR to the NetBeans IDE Palette Manager) which, in turn, automatically creates a JScrollPane as well, this is how you could code the JFrame's constructor: public NewJFrame() { //Initialize the ui generated by the Matisse GUI Builder, which, //for example, adds the JScrollPane to the JFrame ContentPane: initComponents(); //Here I am assuming we are not on Windows, //otherwise use Utilities.isWindows() ? 1 : 0 //from the NetBeans Utilities API: TreeModel treeMdl = new FileTreeModel(File.listRoots()[0]); //Create the Outline's model, consisting of the TreeModel and the RowModel, //together with two optional values: a boolean for something or other, //and the display name for the first column: OutlineModel mdl = DefaultOutlineModel.createOutlineModel( treeMdl, new FileRowModel(), true, "File System"); //Initialize the Outline object: outline1 = new Outline(); //By default, the root is shown, while here that isn't necessary: outline1.setRootVisible(false); //Assign the model to the Outline object: outline1.setModel(mdl); //Add the Outline object to the JScrollPane: jScrollPane1.setViewportView(outline1); } Alternatively, without the NetBeans Matisse GUI Builder and NetBeans Palette Manager, i.e., simply using a standard Java class, you could do something like this: private Outline outline; public NewJFrame() { setDefaultCloseOperation(EXIT_ON_CLOSE); getContentPane().setLayout(new BorderLayout()); TreeModel treeMdl = new FileTreeModel(File.listRoots()[0]); OutlineModel mdl = DefaultOutlineModel.createOutlineModel( treeMdl, new FileRowModel(), true); outline = new Outline(); outline.setRootVisible(false); outline.setModel(mdl); getContentPane().add(new JScrollPane(outline),BorderLayout.CENTER); setBounds(20, 20, 700, 400); } At this point, you can run the JFrame, with this result: So, we see a lot of superfluous info that doesn't look very nice. Let's implement "org.netbeans.swing.outline.RenderDataProvider", as follows: private class RenderData implements RenderDataProvider { @Override public java.awt.Color getBackground(Object o) { return null; } @Override public String getDisplayName(Object o) { return ((File) o).getName(); } @Override public java.awt.Color getForeground(Object o) { File f = (File) o; if (!f.isDirectory() && !f.canWrite()) { return UIManager.getColor("controlShadow"); } return null; } @Override public javax.swing.Icon getIcon(Object o) { return null; } @Override public String getTooltipText(Object o) { File f = (File) o; return f.getAbsolutePath(); } @Override public boolean isHtmlDisplayName(Object o) { return false; } } Now, back in the constructor, add the renderer to the outline: outline1.setRenderDataProvider(new RenderData()); Run the JFrame again and the result should be the same as in the first screenshot above. Look again at the rendering code and note that, for example, you have tooltips:

Last few months I have seen too much code where a HashMap (without any extra synchronization) is used instead of a thread-safe alternative like the ConcurrentHashMap or the less concurrent but still thread-safe HashTable. This is an example of a HashMap used in a home grown cache (used in a multi-threaded environment): interface ValueProvider{V retrieve(K key);}public class SomeCache{private Map map = new HashMap();private ValueProvider valueProvider;public SomeCache(ValueProvider valueProvider){this.valueProvider = valueProvider;}public V getValue(K key){V value = map.get(key);if(value == null){value = valueProvider.get(key);if(value!=null)map.put(key,value);}return value;} There is much wrong with this innocent looking piece of code. There is no happens before relation between the put of the value in the map, and the get of the value. This means that a thread that receives the value from the cache, doesn’t need to see all fields if the value has publication problems (most non thread-safe structures have publication problems). The same goes for the value and the internals (the buckets for example) of the HashMap. This means that updates to the internals of the HashMap while putting, don’t need to be visible to a thread that does the get. So it could be that the state of the cache in main memory is not in an allowed state (some of the changes maybe are stuck in the cpu-cache), and the cache could start behaving erroneous and if you are lucky starts throwing exceptions. And last, but certainly not least, there also is a classic race problem: if 2 threads do a interleaved map.put, the internals of the HashMap can get in an inconsistent state. In most cases an application reboot/redeploy would be the only way to fix this problem. There are other problems with the cache behavior of this code as well. The items don’t have a timeout, so once a value gets in the cache, it stays in the cache. In practice this could lead to web-page that keeps displaying some value, even though in the main repository the value has been updated. An application reboot also is the only way to solve this problem. Using a Common Of The Shelf (COTS) cache would be a much saver solution, even though a new library needs to be added. It is important to realize that a HashMap can be used perfectly in a multi-threaded environment if extra synchronization is added. But without extra synchronization, it is a time-bomb waiting to go off.

One of the newly introduced features in HTML 5 is the ability to mark up reverse ordered lists. These are the same as ordered lists, but instead of counting up from 1, they instead count down towards 1. This can be used, for example, to count down the top 10 movies, music, or LOLCats, or anything else you want to present as a countdown list. In previous versions of HTML, the only way to achieve this was to place a value attribute on each li element, with successively decreasing values. Top 5 TV Series Friends 24 The Simpsons Stargate Atlantis Stargate SG-1 The problem with that approach is that manually specifying each value can be time consuming to write and maintain, and the value attribute was not allowed in the HTML 4.01 or XHTML 1.0 Strict DOCTYPEs (although HTML 5 fixes that problem and allows the value attribute) The new markup is very simple: just add a reversed attribute to the ol element, and optionally provide a start value. If there’s no start value provided, the browser will count the number of list items, and count down from that number to 1. Greatest Movies Sagas of All Time Police Academy (Series) Harry Potter (Series) Back to the Future (Trilogy) Star Wars (Saga) The Lord of the Rings (Trilogy) Since there are 5 list items in that list, the list will count down from 5 to 1. The reversed attribute is a boolean attribute. In HTML, the value may be omitted, but in XHTML, it needs to be written as: reversed="reversed". The start attribute can be used to specify the starting number for the countdown, or the value attribute can be used on an li element. Subsequent list items will, by default, be numbered with the value of 1 less than the previous item. The following example starts counting down from 100, but omits a few items from the middle of the list and resumes from 3. Top 100 Logical Fallacies Used By Creationists False DichotomyAppeal to RidiculeBegging the Question (Circular Logic)StrawmanBare Assertion FallacyArgumentum ad Ignorantiam This article is released under a MIT license and was posted by Lachlan Hunt

This is an introductory tutorial to Spring Batch. It does not aim to provide a complete guide to the framework but rather to facilitate the first contact. Spring Batch is quite rich in functionalities, and this is basically how I started learning it. Keep in mind that we will only be scratching the surface. Before we start All the examples will have the lofty task of printing "Hello World!" though in different ways. They were developed with Spring Batch 1.0. I'll provide a Maven 2 project and I'll run the examples with Maven but of course it is not a requirement to work with Spring Batch. Spring Batch in 2 Words Fortunately, Spring Batch model objects have self-explanatory names. Let's try to enumerate the most important and to link them together: A batch Job is composed of one or more Steps. A JobInstance represents a given Job, parametrized with a set of typed properties called JobParameters. Each run of of a JobInstance is a JobExecution. Imagine a job reading entries from a data base and generating an xml representation of it and then doing some clean-up. We have a Job composed of 2 steps: reading/writing and clean-up. If we parametrize this job by the date of the generated data then our Friday the 13th job is a JobInstance. Each time we run this instance (if a failure occurs for instance) is a JobExecution. This model gives a great flexibility regarding how jobs are launched and run. This naturally brings us to launching jobs with their job parameters, which is the responsibility of JobLauncher. Finally, various objects in the framework require a JobRepository to store runtime information related to the batch execution. In fact, Spring Batch domain model is much more elaborate but this will suffice for our purpose. Well, it took more than 2 words and I feel compelled to make a joke about it, but I won't. So let's move to the next section. Common Objects For each job, we will use a separate xml context definition file. However there is a number of common objects that we will need recurrently. I will group them in an applicationContext.xml which will be imported from within job definitions. Let's go through these common objects: JobLauncher JobLaunchers are responsible for starting a Job with a given job parameters. The provided implementation, SimpleJobLauncher, relies on a TaskExecutor to launch the jobs. If no specific TaskExecutor is set then a SyncTaskExecutor is used. JobRepository We will use the SimpleJobRepository implementation which requires a set of execution Daos to store its information. JobInstanceDao, JobExecutionDao, StepExecutionDao These data access objects are used by SimpleJobRepository to store execution related information. Two sets of implementations are provided by Spring Batch: Map based (in-memory) and Jdbc based. In a real application the Jdbc variants are more suitable but we will use the simpler in-memory alternative in this example. Here's our applicationContext.xml: Hello World with Tasklets A tasklet is an object containing any custom logic to be executed as a part of a job. Tasklets are built by implementing the Tasklet interface. Let's implement a simple tasklet that simply prints a message: public class PrintTasklet implements Tasklet{ private String message; public void setMessage(String message) { this.message = message; } public ExitStatus execute() throws Exception { System.out.print(message); return ExitStatus.FINISHED; } } Notice that the execute method returns an ExitStatus to indicate the status of the execution of the tasklet. We will define our first job now in a simpleJob.xml application context. We will use the SimpleJob implementation which executes all of its steps sequentailly. In order to plug a tasklet into a job, we need a TaskletStep. I also added an abstract bean definition for tasklet steps in order to simplify the configuration: ; Running the Job Now we need something to kick-start the execution of our jobs. Spring Batch provides a convenient class to achieve that from the command line: CommandLineJobRunner. In its simplest form this class takes 2 arguments: the xml application context containing the job to launch and the bean id of that job. It naturally requires a JobLauncher to be configured in the application context. Here's how to launch the job with Maven. Of course, it can be run with the java command directly (you need to specify the class path then): mvn exec:java -Dexec.mainClass=org.springframework.batch.core.launch.support.CommandLineJobRunner -Dexec.args="simpleJob.xml simpleJob" Hopefully, your efforts will be rewarded with a "Hello World!" printed on the console. The code source can be downloaded here. What's Next? This is the first part of 3. In the next part we will improve on this example while the third part will be dedicated to item oriented steps and flat files readers and writers. Hope you find it useful.

The hardest part about learning Hbase (the open source implementation of Google's BigTable), is just wrapping your mind around the concept of what it actually is. I find it rather unfortunate that these two great systems contain the words table and base in their names, which tend to cause confusion among RDBMS indoctrinated individuals (like myself). This article aims to describe these distributed data storage systems from a conceptual standpoint. After reading it, you should be better able to make an educated decision regarding when you might want to use Hbase vs when you'd be better off with a "traditional" database. It's all in the terminology Fortunately, Google's BigTable Paper clearly explains what BigTable actually is. Here is the first sentence of the "Data Model" section: A Bigtable is a sparse, distributed, persistent multidimensional sorted map. Note: At this juncture I like to give readers the opportunity to collect any brain matter which may have left their skulls upon reading that last line. The BigTable paper continues, explaining that: The map is indexed by a row key, column key, and a timestamp; each value in the map is an uninterpreted array of bytes. Along those lines, the HbaseArchitecture page of the Hadoop wiki posits that: HBase uses a data model very similar to that of Bigtable. Users store data rows in labelled tables. A data row has a sortable key and an arbitrary number of columns. The table is stored sparsely, so that rows in the same table can have crazily-varying columns, if the user likes. Although all of that may seem rather cryptic, it makes sense once you break it down a word at a time. I like to discuss them in this sequence: map, persistent, distributed, sorted, multidimensional, and sparse. Rather than trying to picture a complete system all at once, I find it easier to build up a mental framework piecemeal, to ease into it... map At its core, Hbase/BigTable is a map. Depending on your programming language background, you may be more familiar with the terms associative array (PHP), dictionary (Python), Hash (Ruby), or Object (JavaScript). From the wikipedia article, a map is "an abstract data type composed of a collection of keys and a collection of values, where each key is associated with one value." Using JavaScript Object Notation, here's an example of a simple map where all the values are just strings: { "zzzzz" : "woot", "xyz" : "hello", "aaaab" : "world", "1" : "x", "aaaaa" : "y" } persistent Persistence merely means that the data you put in this special map "persists" after the program that created or accessed it is finished. This is no different in concept than any other kind of persistent storage such as a file on a filesystem. Moving along... distributed Hbase and BigTable are built upon distributed filesystems so that the underlying file storage can be spread out among an array of independent machines. Hbase sits atop either Hadoop's Distributed File System (HDFS) or Amazon's Simple Storage Service (S3), while a BigTable makes use of the Google File System (GFS). Data is replicated across a number of participating nodes in an analogous manner to how data is striped across discs in a RAID system. For the purpose of this article, we don't really care which distributed filesystem implementation is being used. The important thing to understand is that it is distributed, which provides a layer of protection against, say, a node within the cluster failing. sorted Unlike most map implementations, in Hbase/BigTable the key/value pairs are kept in strict alphabetical order. That is to say that the row for the key "aaaaa" should be right next to the row with key "aaaab" and very far from the row with key "zzzzz". Continuing our JSON example, the sorted version looks like this: { "1" : "x", "aaaaa" : "y", "aaaab" : "world", "xyz" : "hello", "zzzzz" : "woot" } Because these systems tend to be so huge and distributed, this sorting feature is actually very important. The spacial propinquity of rows with like keys ensures that when you must scan the table, the items of greatest interest to you are near each other. This is important when choosing a row key convention. For example, consider a table whose keys are domain names. It makes the most sense to list them in reverse notation (so "com.jimbojw.www" rather than "www.jimbojw.com") so that rows about a subdomain will be near the parent domain row. Continuing the domain example, the row for the domain "mail.jimbojw.com" would be right next to the row for "www.jimbojw.com" rather than say "mail.xyz.com" which would happen if the keys were regular domain notation. It's important to note that the term "sorted" when applied to Hbase/BigTable does not mean that "values" are sorted. There is no automatic indexing of anything other than the keys, just as it would be in a plain-old map implementation. multidimensional Up to this point, we haven't mentioned any concept of "columns", treating the "table" instead as a regular-old hash/map in concept. This is entirely intentional. The word "column" is another loaded word like "table" and "base" which carries the emotional baggage of years of RDBMS experience. Instead, I find it easier to think about this like a multidimensional map - a map of maps if you will. Adding one dimension to our running JSON example gives us this: { "1" : { "A" : "x", "B" : "z" }, "aaaaa" : { "A" : "y", "B" : "w" }, "aaaab" : { "A" : "world", "B" : "ocean" }, "xyz" : { "A" : "hello", "B" : "there" }, "zzzzz" : { "A" : "woot", "B" : "1337" } } In the above example, you'll notice now that each key points to a map with exactly two keys: "A" and "B". From here forward, we'll refer to the top-level key/map pair as a "row". Also, in BigTable/Hbase nomenclature, the "A" and "B" mappings would be called "Column Families". A table's column families are specified when the table is created, and are difficult or impossible to modify later. It can also be expensive to add new column families, so it's a good idea to specify all the ones you'll need up front. Fortunately, a column family may have any number of columns, denoted by a column "qualifier" or "label". Here's a subset of our JSON example again, this time with the column qualifier dimension built in: { // ... "aaaaa" : { "A" : { "foo" : "y", "bar" : "d" }, "B" : { "" : "w" } }, "aaaab" : { "A" : { "foo" : "world", "bar" : "domination" }, "B" : { "" : "ocean" } }, // ... } Notice that in the two rows shown, the "A" column family has two columns: "foo" and "bar", and the "B" column family has just one column whose qualifier is the empty string (""). When asking Hbase/BigTable for data, you must provide the full column name in the form ":". So for example, both rows in the above example have three columns: "A:foo", "A:bar" and "B:". Note that although the column families are static, the columns themselves are not. Consider this expanded row: { // ... "zzzzz" : { "A" : { "catch_phrase" : "woot", } } } In this case, the "zzzzz" row has exactly one column, "A:catch_phrase". Because each row may have any number of different columns, there's no built-in way to query for a list of all columns in all rows. To get that information, you'd have to do a full table scan. You can however query for a list of all column families since these are immutable (more-or-less). The final dimension represented in Hbase/BigTable is time. All data is versioned either using an integer timestamp (seconds since the epoch), or another integer of your choice. The client may specify the timestamp when inserting data. Consider this updated example utilizing arbitrary integral timestamps: { // ... "aaaaa" : { "A" : { "foo" : { 15 : "y", 4 : "m" }, "bar" : { 15 : "d", } }, "B" : { "" : { 6 : "w" 3 : "o" 1 : "w" } } }, // ... } Each column family may have its own rules regarding how many versions of a given cell to keep (a cell is identified by its rowkey/column pair) In most cases, applications will simply ask for a given cell's data, without specifying a timestamp. In that common case, Hbase/BigTable will return the most recent version (the one with the highest timestamp) since it stores these in reverse chronological order. If an application asks for a given row at a given timestamp, Hbase will return cell data where the timestamp is less than or equal to the one provided. Using our imaginary Hbase table, querying for the row/column of "aaaaa"/"A:foo" will return "y" while querying for the row/column/timestamp of "aaaaa"/"A:foo"/10 will return "m". Querying for a row/column/timestamp of "aaaaa"/"A:foo"/2 will return a null result. sparse The last keyword is sparse. As already mentioned, a given row can have any number of columns in each column family, or none at all. The other type of sparseness is row-based gaps, which merely means that there may be gaps between keys. This, of course, makes perfect sense if you've been thinking about Hbase/BigTable in the map-based terms of this article rather than perceived similar concepts in RDBMS's. And that's about it Well, I hope that helps you understand conceptually what the Hbase data model feels like. As always, I look forward to your thoughts, comments and suggestions.

When asking the question how does functional programming help me with concurrent programming? The standard response tends to be functional programming use immutable data structures, read-only data structures can be shared between threads without issues, end of problem. Except it isn’t. Immutable data structures have a different set of problems associated with them when working on concurrent problems. This post will examine what these problems are, and then show that this is just a special case of a more general set of problems when working with immutable data structures. Finally will start taking a look at how we solve some of these problems, but in a single thread environment first of all. First let’s frame the problem by looking at how imperative programs work with threads. In a classic imperative/OO languages programmers tend to use either instance or static member variables to send messages between threads, let’s look a fragment of C# that does something classically multi-threaded: object workQueueLock = new object(); Queue workQueue = new Queue(); // this method runs on its own thread private void Worker() { while (true) { // define a work item attempt to retrive work from the queue WorkItem item = null; lock (workQueueLock) { if (workQueue.Count > 0) { item = workQueue.Dequeue(); } } // check if we have work to do, otherwise sleep if (item != null) { // do some work } else { Thread.Sleep(QueuePollInterval); } } } // an even that resets our flag private void Some_Event(object sender, WorkEventArgs ea) { lock (workQueueLock) { workQueue.Enqueue(ea.WorkItem); } } I wouldn’t recommend you use this naive version of a work queue, but the above code is straight forward enough to understand easily and illustrate the typical way imperative programs communicate between threads. We have a member variable “workQueue” that controls stores the work to be done, the method “Worker” is designed to read from this queue and if there’s some work to do, do the work, otherwise sleep till it’s time to poll the queue again. We use “workQueue” again in “Some_event” to send a message to “Worker”, to enqueue some work for it to do. It’s easy to see that mutation of the variable “workQueue” is essential to get this to work; if we couldn’t change the content of “workQueue” then we couldn’t send the message. It’s also easy to see that we now have a huge number of implementation choices: Do we lock on the queue, or have separate lock? What’s the shortest possible time we can hold the lock for (to avoid other threads be blocked when they want to write to the queue)? How long do we sleep for before polling the queue? Too shorter time and we risk wasting too much processor time polling the queue, too longer time and risk that the queue because unreactive because the worker wastes too much time sleeping when there’s work to be done. In pure functional programming there are no variables or mutation, so the above scenario simply isn’t possible. Sure, F# isn’t a pure function language, actually most functional languages aren’t, so you can indeed use mutable data structures to implement something similar to the C# fragment we showed earlier, but that’s not the point we want to learn how to use immutable data structures. To fully understand the limitations of immutable data structures, let’s look at another C# example do something simpler. Imagine that we want compute a key of a value then store it in a member variable, a dictionary in this case, for later use: Dictionary myDict = new Dictionary(); public void ReceiveValue(string val) { myDict.Add(ComputerKey(val), val); } Now let’s think about how we can translate this into F#. Firstly, if don’t mind being dirty and mutable we can translate this fragment verbatim: type Store() = let myDict = new Dictionary() member x.ReceiveValue (value:string) = myDict.Add(x.ComputeKey value, value) However, if we don’t want to be mutable it’s not quite so straight forward. F# contains a type called “Map”, which is very similar to a Dictionary except that it is immutable. When you add a new item to a map you don’t change the map you create a new version of the map with the new key added. So here is how our store class would look to if we used an immutable “Map” data structure: type ComputeKeys(myDict:Map) = member x.ReceiveValue (value:string) = new ComputeKeys(myDict.Add(x.ComputeKey value, value)) The important thing to notice is that we now have no “let” definition where we store our dictionary; instead the dictionary is passed to the class constructor. So our constructor receives a “Map”, and when we use our “ReceiveValue” method we create a new instance of the “ComputerKeys” which contains the newly created value. I think the type signature really helps us understand what’s going on: type ComputeKeys = class end with member ReceiveValue : value:string -> ComputeKeys new : myDict:Map -> ComputeKeys end This is pretty much the revelation of immutable data structures, “let” definitions become merely short conveniences for values, not memory location that can be updated at a later data if we want to. These new values are all held on the threads stack, if were being pure and fully immutable that we have no memory locations that we can write them to. Okay let’s have a look at how we might use these two classes: /// wraps a Dictionary to provide /// some hashing and printing functions type Store() = // the dictionary that stores the values let myDict = new Dictionary() /// receive a value, hash it store it member x.ReceiveValue (value:string) = myDict.Add(x.ComputeKey value, value) /// computers the hash (a bit naff for now) member x.ComputeKey (value:string) = value.GetHashCode().ToString() /// prints the stored values override x.ToString() = let stringWriter = new StringWriter() for key in myDict.Keys do stringWriter.WriteLine("{0}: {1}", key, myDict.[key]) stringWriter.ToString() let useStore() = let store = new Store() store.ReceiveValue("One") store.ReceiveValue("Two") store.ReceiveValue("Three") printfn "%s" (store.ToString()) The mutable version needs little explanation, it is classical imperative programming, we create an instance of store then add values to our store, and finally we print them out. Now compare this with the immutable version: /// wraps a Map to provide /// some hashing and printing functions type ComputeKeys(myDict:Map) = /// receive a value, hash it, return the new value member x.ReceiveValue (value:string) = new ComputeKeys(myDict.Add(x.ComputeKey value, value)) /// computers the hash (a bit naff for now) member x.ComputeKey (value:string) = value.GetHashCode().ToString() /// prints values in the map override x.ToString() = myDict.Fold (fun key value acc -> Printf.sprintf "%s \r\n%s: %s" acc key value) "" let useComputeKeys() = let keysEmpty = new ComputeKeys(Map.empty) let keysOne = keysEmpty.ReceiveValue("One") let keysTwo = keysOne.ReceiveValue("Two") let keysThree = keysTwo.ReceiveValue("Three") printfn "%s" (keysThree.ToString()) The thing to notice here is how similar using the immutable ComputeKeys class is to using the Store class. We create an instance of the class, we add values to it, and then finally we print it. The only difference being that we need to catch the value returned from RecieveValue and use this value in the next step. Here we’ve used different names for each instance – to illustrate that each let binding is to a different instances, but we don’t need to do that we can reuse the same name to save inventing new names: let useComputeKeysAlt() = let keys = new ComputeKeys(Map.empty) let keys = keys.ReceiveValue("One") let keys = keys.ReceiveValue("Two") let keys = keys.ReceiveValue("Three") printfn "%s" (keys.ToString()) The take away from this is that programming with immutable data structures when we have one thread of execution is not that different to programming with imperative mutable structures, we just have to remember that every time we want to make a change we copy and add rather than update. Wrapping It Up In this inductor post we’ve looked at why mutation is important to classical concurrent programming, and indeed classical imperative programming. Then we looked at immutable data structures and compared they way that they work to mutable data structures. In the next post we’ll dig deeper into immutable data structures, to really get a feel for the programming possibilities they offer. Then in the post after that we’ll look at concurrent programming with immutable data structures and finally get to grips the problem we posed ourselves in the first couple of paragraphs of this post. Patience is a virtue and good things come to those who wait J.

The star schema represents data as a table of facts (measurable values) that are associated with the various dimensions of the fact. Common dimensions include time, geography, organization, product and the like. I'm working with some folks whose facts are a bunch of medical test results, and the dimensions are patient, date, and a facility in which the tests were performed. I got an email with the following situation: "a client who is processing gigs of incoming fact data each day and they use a host of C/C++, Perl, mainframe and other tools for their incoming fact processing and I've seriously considered pushing Python in their organization.". Here are my thoughts on using Python for data warehousing when you've got Gb of data daily. Small Dimensions The pure Python approach only works when your dimension will comfortably fit into memory -- not a terribly big problem with most dimensions. Specifically, it doesn't work well for those dimensions which are so huge that the dimensional model becomes a snowflake instead of a simple star. When dealing with a large number of individuals (public utilities, banks, medical management, etc.) the "customer" (or "patient") dimension gets too big to fit into memory. Special bridge-table techniques must be used. I don't think Python would be perfect for this, since this involves slogging through a lot of data one record at a time. However, Python is considerably faster than PL/SQL. I don't know how it compares with Perl. Any programming language will be faster than any SQL procedure, because there's no RDBMS overhead. For all small dimensions. Load the dimension values from the RDBMS into a dict with a single query. Read all source data records (ideally from a flat file); conform the dimension, tracking changes; write a result record with the dimension FK information to a flat file. Iterate through the dimension dictionary and persist the dimension changes. The details vary with the Slowly Changing Dimension (SCD) rules you're using. The conformance algorithm is is essentially the following: row= Dimension(...) ident= ( row.field, row.field, row.field, ... ) dimension.setdefault( ident, row ) In some cases (like the Django ORM) this is called the get-or-create query. The Dimension Bus For BIG dimensions, I think you still have to implement the "dimension bus" outlined in The Data Warehouse Toolkit. To do this in Python, you should probably design things to look something like the following. For any big dimensions. Use an external sort-merge utility. Seriously. They're way fast for data sets too large to fit into memory. Use CSV format files and the resulting program is very tidy. The outline is as follows: First, sort the source data file into order by the identifying fields of the big dimension (customer number, patient number, whatever). Second, query the big dimension into a data file and sort it into the same order as the source file. (Using the SQL ORDER BY may be slower than an external sort; only measurements can tell which is faster.) Third, do a "match merge" to locate the differences between the dimension and the source. Don't use a utility like diff, it's too slow. This is a simple key matching between two files. The match-merge loop looks something like this. src= sourceFile.next() dim= dimensionFile.next() try: while True: src_key = ( src['field'], src['field'], ... ) dim_key= ( dim['field'], dim['field'], ... ) if src_key < dim_key: # missing some dimension values update_dimension( src ) src= sourceFile.next() elif dim_key < src_key: # extra dimension values dim= dimensionFile.next() else: # src and dim keys match # check non-key attributes for dimension change. src= sourceFile.next() except StopIteration, e: # if source is at end-of-file, that's good, we're done. # if dim is at end of file, all remaining src rows are dimension updates. for src in sourceFile: update_dimension( src ) At the end of this pass, you'll accumulate a file of customer dimension adds and changes, which is then persisted into the actual customer dimension in the database. This pass will also write new source records with the customer FK. You can also handle demographic or bridge tables at this time, too. Fact Loading The first step in DW loading is dimensional conformance. With a little cleverness the above processing can all be done in parallel, hogging a lot of CPU time. To do this in parallel, each conformance algorithm forms part of a large OS-level pipeline. The source file must be reformatted to leave empty columns for each dimension's FK reference. Each conformance process reads in the source file and writes out the same format file with one dimension FK filled in. If all of these conformance algorithms form a simple OS pipe, they all run in parallel. It looks something like this. src2cvs source | conform1 | conform2 | conform3 | load At the end, you use the RDBMS's bulk loader (or write your own in Python, it's easy) to pick the actual fact values and the dimension FK's out of the source records that are fully populated with all dimension FK's and load these into the fact table. I've written conformance processing in Java (which is faster than Python) and had to give up on SQL-based conformance for large dimensions. Instead, we did the above flat-file algorithm to merge large dimensions. The killer isn't the language speed, it's the RDBMS overheads. Once you're out of the database, things blaze. Indeed, products like the syncsort data sort can do portions of the dimension conformance at amazing speeds for large datasets. Hand Wringing "But," the hand-wringers say, "aren't you defeating the value of the RDBMS by working outside it?" The answer is NO. We're not doing incremental, transactional processing here. There aren't multiple update transactions in a warehouse. There are queries and there are bulk loads. Doing the prep-work for a bulk load outside the database is simply more efficient. We don't need locks, rollback segments, memory management, threading, concurrency, ACID rules or anything. We just need to match-merge the large dimension and the incoming facts.

To convert a Java Project to a Web Project switch to or open the Resource Perspective of the project, in the root of the project. Open the .project file and make sure the builders and natures are present that are needed for a web project. See the example below, the name should be the name of your project, the most important nodes are the nature children in the natures node: testProjectorg.eclipse.jdt.core.javabuilderorg.eclipse.wst.common.project.facet.core.builderorg.eclipse.wst.validation.validationbuilderorg.eclipse.wst.common.project.facet.core.natureorg.eclipse.jdt.core.javanatureorg.eclipse.wst.common.modulecore.ModuleCoreNatureorg.eclipse.jem.workbench.JavaEMFNature Once you’ve updated the .project file you can close the file and right click and choose properties on the project. When the properties window opens click on Project Facets. The Facets grid is probably empty, click the Modify Project button. Check the Dynamic Web Module and Java Facets, choose the Java and Servlet version that applies to your project. Click Next and specify the existing or new location of your src and web content directories. Click Finish. As a final step I would recommend modifying the build path to compile your source directly into your /WEB-INF/classes directory by selecting Java Build Path and modifying the Default output directory. Now you should be able to create a local tomcat server, or if you’ve already created one you should be able to add the project to the server by right clicking the server and choosing Add and Remove Projects. Original article at http://greatwebguy.com/programming/eclipse/converting-a-java-project-to-a-dynamic-web-project-in-eclipse/.

JSR 310 aims to modernize the date and calendar classes. The goal is to provide a more advanced and comprehensive model for date and time than those found in the Date and Calendar APIs. The JSR's leaders, Stephen Colebourne and Michael Nascimento, are presenting their work at JavaOne and give an overview below. Firstly, please briefly introduce yourselves. Michael Nascimento. I'm a senior technical consultant at Summa technologies and the founder of the Genesis open source project. I have also served as an expert on a few JSRs, such as the Common Annotations for the Java Platform (JSR-250). Stephen Colebourne. I am employed building travel e-commerce booking engines and am involved with many open source projects, such as Apache Commons and JodaTime. I am involved in this JSR because of my JodaTime project. JodaTime? What's that? Stephen: JodaTime provides a complete replacement of the date and time classes in the JDK: public boolean isAfterPayDay(DateTime datetime) { if (datetime.getMonthOfYear() == 2) { // February is month 2!! return datetime.getDayOfMonth() > 26; } return datetime.getDayOfMonth() > 28; } public Days daysToNewYear(LocalDate fromDate) { LocalDate newYear = fromDate.plusYears(1).withDayOfYear(1); return Days.daysBetween(fromDate, newYear); } public boolean isRentalOverdue(DateTime datetimeRented) { Period rentalPeriod = new Period().withDays(2).withHours(12); return datetimeRented.plus(rentalPeriod).isBeforeNow(); } public String getBirthMonthText(LocalDate dateOfBirth) { return dateOfBirth.monthOfYear().getAsText(Locale.ENGLISH); } What are the main things that are wrong with the current date and time classes? Stephen: The existing classes are pretty bad—probably the worst APIs in the JDK. They're buggy, mutable, cumbersome, many bugs, and they tend not to be threadsafe. Michael: The original date class comes from JDK 1.0. At the time, James Gosling tried to follow the related functions in C and didn't put much force into designing them from scratch. For example, they can't be internationalized and only local timezones are supported. Stephen: Right. The Gregorian calendar class is a direct port of the C-class, such as "January = 0". So, if you enter the month "12", the month is January because the algorithm wraps around. The algorithm performs calculations such as this that you don't expect. For example, with the Gregorian calendar class, getYear(), getMonth(), and getDay() are quick, while if you call combinations of getyear(), setyear() (and getMonth() setMonth(), and so on), performance will be bad because lots of calculations are done unexpectedly. Politely put, one can describe these classes as exhibiting "unusual performance characteristics". Why has it taken so long to fix these various problems? Stephen: People have known of these problems for several years. Some attempts have been made to fix the Calendar class, but it only got worse. Fixing these issues once and for all has never been a high enough priority. So why now and why you? Stephen: I started JodaTime in 2000/2001 and gradually solved the standard date and time class problems, releasing it in 2003. My solution has been picked up across the board, from small applications to the largest advertizing systems in the world. The point is that I wanted the solution to exist a few years as JodaTime, before heading into a JSR so that all the issues would have been identified in preparation for the JSR. In a nutshell, what does JodaTime offer me? Michael: Firstly, a better quality API. Stephen: Secondly, JodaTime supports a number of additional concepts. Firstly, "periods", such as if you wanted to store the concept of 5 weeks and 3 days. Secondly, "intervals", so that you'll be able to store the interval between the start of JavaOne and its end, i.e., for example, from Monday May 5, 9 a.m. to May 9, 3 p.m. Thirdly, an updated timezone implementation to make it easy to pick up timezone changes, which could even be on an annual basis. Finally, handling of different calendar systems, such as Islamic calendar systems / Coptic calendar systems, and so on, which don't exist in the standard JDK. Michael: The third point is why I got interested in this JSR in the first place. I'm from Brazil where the daylight saving systems change each year and there's always one or two weeks of chaos. I asked myself why things go wrong every year around this issue. Stephen. Possibly we could offer a solution consisting of a JAR file with the latest set of rules, which you could then put on the classpath. However, sometimes you'd need both sets of rules at the same time. We're still thinking about these situations and ought to be able to come up with something. By the way, where does the name "Joda" come from? Stephen: "Joda" was a 4 letter domain name starting with "J" that was free in 2003. I simply typed random things beginning with "J" and found that that one was free... Where is the JSR process now? Michael: We are progressing it in an open manner. All discussions are on public mailing lists and Wikis. All repositories are open and Issuezilla is open. Stephen: We are using java.net to build a reference implementation and a testing kit in Subversion. People can go there and try it out. It is all "work in progress". The basic API is there. Right now, parsing needs to be finished and some loose ends need to be tidied up. Parsing, intervals, and multiple calendar systems are missing at the moment. Can you say something about the JSR's timeline? Stephen: We hope that we'll be in Java 7, but given that there's no date for it, there's no guarantee that we'll finish in time. We received a little bit of funding from the OpenJDK challenge to get to early draft review by August. Michael: It's really important that people get involved, the last chance to influence design aspects is the early draft review, scheduled for August, which is coming near. Two previous attempts have been made for rewriting these classes and it's unlikely there'll be another one after ours. So it is really important to let your voice be heard because the more feedback we get the better. Stephen: There's been good quality feedback. We've had suggestions consisting of sample implementations of intervals, people pointing to different ISO specifications, and suggestions to expand into areas outside our scope. People should take a look at the algorithms too. Maybe someone could come up with better algorithms than those that we already have. Michael: We've also been nominated for a JCP Program Award, probably because we're the main examples of individuals, rather than a company, leading a JSR. The results will be announced on Tuesday during JavaOne. Will you present something around your JSR at JavaOne? Michael: Our technical session on Thursday at 1.30 is completely full and there's a repeat session on Friday at the same time, that is, at 1.30. In the session, we will cover all the basic classes, show examples of the code and how to get started with it. Stephen: There'll be little bit of explanation around the design principles, with examples of how bad the current date and time classes are. There'll also be a small puzzler, asking participants to identify the number of bugs in an existing bit of JDK code... Further Reading JSR 310 JSR 310 Technical Sessions at JavaOne JSR 310 General Purpose Area for Anyone to Leave Messages JSR 310 Mailing List Stephen Colebourne's blog Michael Nascimento's blog JCP Program's Award Nominations

Andre Mare's series on "Gang of Four" design patterns continues. First, he covered the Builder Pattern, next the Factory Method Pattern. Today he continues with the "Abstract Factory Pattern". Read on for all the details, diagrams, and sample code! -- Geertjan Wielenga, JavaLobby Zone Leader Intent Provide an interface for creating families of related or dependent objects without specifying their concrete classes. - Gof Type Object Creational Solution The Abstract Factory Pattern defines an interface with a set of methods to create a family of related products. The family of related objects is defined through a set of product types. The implementation of the product types is delegated to a set of concrete product subclasses. The creation of the concrete product classes is implemented by series of concrete factory classes. The Abstract Factory Pattern defers the creation of the concrete products to the concrete factory classes that implements the abstract factory. The client object is decoupled from the concrete product classes and the concrete factory classes through the Abstract Factory interface. The core of the Abstract Factory Pattern is to create a group of related objects that might have different implementations. The system is therefore independent of the implementation of the product types. The Abstract Factory Pattern also enables the system to replace a set of related product classes with another set, by changing the concrete factory class. The Abstract Factory Pattern consists of an AbstractFactory, ConcreteFactory, AbstractProduct, ConcreteProduct and Client. The AbstractFactory defines a factory type that list operations for creating the set of related abstract product types. The ConcreteFactory implements the list of operations and create the concrete product objects that are associated with the specific concrete factory class. The AbstractProduct declares the operations available for the specific product type. The implementation of the product type is delegated to the subclasses of the product type. The ConcreteProduct is created by a specific concrete factory object and is the realization of a specific product type. The client system is decoupled from the actual concrete product class, but invokes the implementation through the abstract product. The Client object is decoupled from the ConcreteFactory and ConcreteProduct objects and work with the interfaces declared by the AbstractFactory and AbstractProduct types. The Abstract Factory Pattern can be implemented using the Factory Method Pattern, Prototype Pattern or the Singleton Pattern. The ConcreteFactory object can be implemented as a Singleton as only one instance of the ConcreteFactory object is needed. Structure Java Sample Code Download: Greek Salad Instruction The following example illustrates the use of the Abstract Factory pattern. The Greek Salad Instruction example illustrates the creation of a family of related objects that supply the instructions for making different types of Greek Salads. The example consists of the following classes: SaladInstructionsKit.java - (AbstractFactory) DicedGreekSaladInstructionFactory.java - (ConcreteFactory) SlicedGreekSaladInstructionFactory.java - (ConcreteFactory) CucumberInstructions.java - (AbstractProduct) TomatoInstructions.java - (AbstractProduct) SlicedTomatoInstructions.java - (ConcreteProduct) DicedCucumberInstructions.java - (ConcreteProduct) DicedTomatoInstructions.java - (ConcreteProduct) SlicedCucumberInstructions.java - (ConcreteProduct) GreekSaladInstructionsClient.java - (Client) MainClass.java - (class contains main method) GreekSaladInstructionsClient.java The GreekSaladInstructionsClient class makes use of the AbstractFactory and AbstractProduct classes to determine the instructions on making a Greek Salad. Depending on the ConcreteFactory, the salad may be diced or sliced. The class will invoke the appropriate methods on the concrete product classes through the abstract product types. SaladInstructionsKit.java The SaladInstructionsKit defines a factory type that list operations for creating the set of related abstract product types. The Abstract Factory defers the creation of the concrete product classes to the concrete factory classes. Each specific concrete factory class will create a specific concrete product class. TomatoInstructions.java The TomatoInstructions declares the operations available for the specific product type. The implementation of the product type is delegated to the subclasses of the product type. CucumberInstructions.java The CucumberInstructions declares the operations available for the specific product type. The implementation of the product type is delegated to the subclasses of the product type. SlicedGreekSaladInstructionFactory.java The SlicedGreekSaladInstructionFactory implements the list of operations and create the concrete product objects that is associated with the specific concrete factory class. The concrete factory creates specific concrete product classes to create a sliced Greek Salad. SlicedCucumberInstructions.java The SlicedCucumberInstructions is created by a specific concrete factory object and is the realization of a specific product type. SlicedTomatoInstructions.java The SlicedTomatoInstructions is created by a specific concrete factory object and is the realization of a specific product type. Sequence Diagram Sequence Diagram by "Yanic Inghelbrecht" with Trace Modeler Abstract Factory vs. Factory Method The methods of an Abstract Factory are implemented as Factory Methods. Both the Abstract Factory Pattern and the Factory Method Pattern decouples the client system from the actual implementation classes through the abstract types and factories. The Factory Method creates objects through inheritance where the Abstract Factory creates objects through composition. See Factory Method Pattern. References Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. Design Patterns: Elements of Reusable Object-Oriented Software. Addison Wesley, 1995

Some time ago I found a couple of posts talking about how to obfuscate a NetBeans RCP module (here and here). Getting some parts of the ant targets presented in the previous post, this one presents a simple target that allows to obfuscate a normal Java library. For this, you need to have installed the obfuscator ProGuard. Take into account I am talking about obfuscating a Java library. This implies the obfuscation is lighter than if you obfuscate a closed application, that is, all public methods and interfaces must maintain its name (if not you can call your library methods anymore). Open your build.xml Java application file and paste this target: Special attention to these couple of lines:

Lately, I’ve been experimenting more with OSGi, and I want to share some of the examples I’ve put together. The examples involve Felix, Spring Dynamic Modules, and Jetty, though could easily be used with Equinox. Once I’m finished with these exercises, I’m hoping to compare and contrast the different approaches I’ve taken, as well as comparing embedded Jetty with the Equinox Servlet Bridge. I’m a believer that OSGi is a disruptive technology that stands to transform Java development as we know it today. There are numerous OSGi tutorials, blogs, and samples posted around the web. My OSGi resources page lists some of these, and if you know of other good resources not listed, please let me know. When I experiment with a new technology, I like to focus exclusively on the technology itself, without code generators, wizards, or other utilities that do half the work for me. I feel it maximizes the experience. To that end, all of my exercises avoid using tools like Maven or Eclipse. I find Maven confusing and using Eclipse for some of these smaller exercises is overkill. Save for a few necessary tools like Ant and the Felix framework itself, I’ll roll everything by hand. Hopefully, this helps clarify the core essence of OSGi. The first sample is the canonical HelloWorld example where I create two simple bundles - a client.jar and service.jar. Again, in OSGi parlance, a bundle is a .jar file. You can find the working code in My Google Code repository (the HelloWorld project), complete with the Ant build script, the bundle cache, and a .bat or .sh script to start Felix depending on your OS. The only two prerequisites for these samples is Felix (I used version 1.0.0) and Ant, which you’ll have to download separately. Let’s walk through the creation of these two simple bundles. First, let’s look at HelloConsumer in client.jar. HelloConsumer uses the HelloService to get the hello and goodbye messages when the client.jar bundle is started and stopped, respectively. HelloConsumer implements OSGi’s BundleActivator, meaning Felix will invoke the start method when the bundle is started, and the stop method when the bundle is stopped. As seen on line 26, HelloConsumer obtains a reference to the HelloService using the OSGi ServiceTracker class. package com.extensiblejava.hello.client; import com.extensiblejava.hello.service.HelloService; import org.osgi.framework.BundleActivator; import org.osgi.framework.BundleContext; import org.osgi.framework.ServiceReference; import org.osgi.util.tracker.ServiceTracker; public class HelloConsumer implements BundleActivator { private ServiceTracker helloWorldTracker; private HelloService helloService; public void setService(HelloService helloService) { this.helloService = helloService; } public void removeService() { this.helloService = null; } public void start(BundleContext context) throws Exception { helloWorldTracker = new ServiceTracker(context, HelloService.class.getName(), null); helloWorldTracker.open(); HelloService hello = (HelloService) helloWorldTracker.getService(); if (hello == null) { System.out.println("Hello service unavailable on HelloConsumer start"); } else { System.out.println(hello.sayHello()); } } public void stop(BundleContext context) { HelloService hello = (HelloService) helloWorldTracker.getService(); if (hello == null) { System.out.println("Hello service unavailable on HelloConsumer stop"); } else { System.out.println(hello.sayGoodbye()); } helloWorldTracker.close(); } } The HelloService and HelloServiceImpl form the OSGi service. HelloService is a simple Java interface that defines the API, while HelloServiceImpl implements the BundleActivator and is the class invoked when the server bundle is started and stopped. As seen on line 18, HelloServiceImpl registers itself as an OSGi service. Without registration, HelloConsumer would not be able to use HelloService as an OSGi service. package com.extensiblejava.hello.service.impl; import java.util.Properties; import com.extensiblejava.hello.service.HelloService; import org.osgi.framework.BundleActivator; import org.osgi.framework.BundleContext; import org.osgi.framework.ServiceListener; import org.osgi.framework.ServiceEvent; import org.osgi.framework.ServiceRegistration; public class HelloServiceImpl implements HelloService, BundleActivator { private ServiceRegistration registration; public void start(BundleContext context) { Properties props = new Properties(); props.put("Language", "English"); registration = context.registerService(HelloService.class.getName(), this, props); } public void stop(BundleContext context) { } public String sayHello() { return "Hello World!! "; } public String sayGoodbye() { return "Goodbye World!!"; } } There’s a bit more magic here that makes this all work. A wonderful aspect of OSGi is that dependencies must be managed explicitly, with each bundle’s manifest declaring the packages the bundle imports and exports. Bundle manifests specify other key pieces of information, too. Notably, it tells the OSGi environment of the BundleActivator to invoke on start and stop. If a bundle imports a package, then another bundle within that OSGi run-time must export that same package. The client bundle manifest imports the package containing HelloService while the service bundle manifest exports that same package. Were these imports and exports not explicitly declared, we’d receive OSGi run-time errors. In our example above, HelloServiceImpl registers itself as an OSGi service allowing clients to obtain a reference to HelloService using the OSGi ServiceTracker. The client and service OSGi bundles can be deployed to any OSGi run-time. I’ve used Felix for this example, but could have used Equinox just as easily. To run these examples, you can checkout the code from the Google Code repository. Since I include the bundle cache in the repository, you should be able to start felix and experiment with OSGi. You’ll likely have to modify the start script (OS-based) to ensure Felix is in your classpath. Upon starting Felix, you’ll be asked to enter a profile name. To use the bundle cache included with the example, simply use HelloWorld as your profile. If you’re feeling a bit more adventurous, you can make some changes to the HelloServiceImpl message and rebuild the project by invoking the Ant build script. Once compiled, move back into the Felix shell and update the service bundle using the Felix update command. For a listing of all Felix commands, simply type ‘help’. If you want to deploy the bundles to your own Felix cache, restart Felix and enter a different profile name. Any name will do, and Felix will create a new bundle cache for you. Here are some more suggested steps to build, install, and continue experimenting with the bundles and OSGi: Build service by executing ant within service directory Build client by executing ant within client directory Run startfelix.bat or startfelix.sh depending on your OS install the bundles from the felix shell install file:service/bin/service.jar install file:client/bin/client.jar ps start {service-bundle-id} start {client-bundle-id} Experiment by starting and stopping client and service to get a feel for OSGi. Now change the service message printed in HelloServiceImpl.java and compile. Then do the following while client is running. stop {service-bundle-id} update {service-bundle-id} start {service-bundle-id} stop {client-bundle-id} When stopping the client bundle, you should see a different goodbye message than what you saw in step 4. OSGi offers a very dynamic and adaptable run-time environment. Even when not using OSGi services, reuse across bundles can occur so long as the package dependencies are explicitly managed in the bundle manifests. The benefit with OSGi services is that the OSGi run-time manages the service lifecycle, however. Many of the presentations I give on architecture & design talk about the importance of managing .jar relationships, and I’ve long felt that the .jar file is a great candidate as a first class component on the Java platform. In the next post, I’ll explore the simple benefits of an incredibly important heuristic that states we should “separate interface from implementation.” You can get a head start by taking a look at the HelloWorldSpec project on My Google Code repository. http://techdistrict.kirkk.com/

WSDL is a version of XML used to better work with web severs. In this post, we'll learn how to better use it alongside the Java language.

Migrate4j is a migration tool for java, similar to Ruby's db:migrate task. Unlike other Java based migration tools, database schema changes are defined in Java, not SQL. This means your migrations can be applied to different database engines without worrying about whether your DDL statements will still work. Schema changes are defined in Migration classes, which define "up" and "down" methods - "up" is called when a Migration is being applied, while "down" is called when it is being rolled back. A simple Migration, which simply adds a table to a database, is written as: package db.migrations; import static com.eroi.migrate.Define.*; import static com.eroi.migrate.Define.DataTypes.*; import static com.eroi.migrate.Execute.*; import com.eroi.migrate.Migration; public class Migration_1 implements Migration { public void up() { createTable( table("simple_table", column("id", INTEGER, primaryKey(), notnull()), column("desc", VARCHAR, length(50), defaultValue("NA")))); } public void down() { dropTable("simple_table"); } } This Migration can be applied at application startup, from an Ant task (included in migrate4j) or from the command line. Migrate4j will only apply the migration if it has not yet been applied. LIkewise, migrate4j will roll back the migration when instructed, only if the migration has been previously applied. The migrate4j team is happy to announce a new release which adds improved usability (simplified syntax), additional schema changes and support for more database products. While migrate4j does not yet have support for all database products, we are actively seeking developers interested in helping fix this situation. Visit http://migrate4j.sourceforge.net for more information on how migrate4j can simplify synchronizing your databases. To obtain migrate4j, go to http://sourceforge.net/projects/migrate4j and download the latest release. For questions or to help with future development of migrate4j, email us at migrate4j-users AT lists.sourceforge.net (replacing the AT with the "at symbol").

Formerly called ACEGI Security for Spring, the re-branded Spring Security 2.0 has delivered on its promises of making it simpler to use and improving developer productivity. Already considered as the Java platform's most widely used enterprise security framework with over 250,000 downloads from SourceForge, Spring Security 2.0 provides a host of new features. This article outlines how to convert your existing ACEGI based Spring application to use Spring Security 2.0. What is Spring Security 2.0 Spring Security 2.0 has recently been released as a replacement to ACEGI and it provides a host of new security features: Substantially simplified configuration. OpenID integration, single sign on standard. Windows NTLM support, single sign on against Windows corporate networks. Support for JSR 250 ("EJB 3") security annotations. AspectJ pointcut expression language support. Comprehensive support for RESTful web request authorization. Long-requested support for groups, hierarchical roles and a user management API. An improved, database-backed "remember me" implementation. New support for web state and flow transition authorization through the Spring Web Flow 2.0 release. Enhanced WSS (formerly WS-Security) support through the Spring Web Services 1.5 release. A whole lot more... Goal Currently I work on a Spring web application that uses ACEGI to control access to the secure resources. Users are stored in a database and as such we have configured ACEGI to use a JDBC based UserDetails Service. Likewise, all of our web resources are stored in the database and ACEGI is configure to use a custom AbstractFilterInvocationDefinitionSource to check authorization details for each request. With the release of Spring Security 2.0 I would like to see if I can replace ACEGI and keep the current ability to use the database as our source of authentication and authorization instead of the XML configuration files (as most examples demonstrate). Here are the steps that I took... Steps The first (and trickiest) step was to download the new Spring Security 2.0 Framework and make sure that the jar files are deployed to the correct location. (/WEB-INF/lib/) There are 22 jar files that come with the Spring Security 2.0 download. I did not need to use all of them (especially not the *sources packages). For this exercise I only had to include: spring-security-acl-2.0.0.jar spring-security-core-2.0.0.jar spring-security-core-tiger-2.0.0.jar spring-security-taglibs-2.0.0.jar Configure a DelegatingFilterProxy in the web.xml file. springSecurityFilterChain org.springframework.web.filter.DelegatingFilterProxy springSecurityFilterChain /* Configuration of Spring Security 2.0 is far more concise than ACEGI, so instead of changing my current ACEGI based configuration file, I found it easier to start from a empty file. If you do want to change your existing configuration file, I am sure that you will be deleting more lines than adding. The first part of the configuration is to specifiy the details for the secure resource filter, this is to allow secure resources to be read from the database and not from the actual configuration file. This is an example of what you will see in most of the examples: Replace this with: The main part of this piece of configuration is the secureResourceFilter, this is a class that implements FilterInvocationDefinitionSource and is called when Spring Security needs to check the Authorities for a requested page. Here is the code for MySecureResourceFilter: package org.security.SecureFilter; import java.util.Collection; import java.util.List; import org.springframework.security.ConfigAttributeDefinition; import org.springframework.security.ConfigAttributeEditor; import org.springframework.security.intercept.web.FilterInvocation; import org.springframework.security.intercept.web.FilterInvocationDefinitionSource; public class MySecureResourceFilter implements FilterInvocationDefinitionSource { public ConfigAttributeDefinition getAttributes(Object filter) throws IllegalArgumentException { FilterInvocation filterInvocation = (FilterInvocation) filter; String url = filterInvocation.getRequestUrl(); // create a resource object that represents this Url object Resource resource = new Resource(url); if (resource == null) return null; else{ ConfigAttributeEditor configAttrEditor = new ConfigAttributeEditor(); // get the Roles that can access this Url List roles = resource.getRoles(); StringBuffer rolesList = new StringBuffer(); for (Role role : roles){ rolesList.append(role.getName()); rolesList.append(","); } // don't want to end with a "," so remove the last "," if (rolesList.length() > 0) rolesList.replace(rolesList.length()-1, rolesList.length()+1, ""); configAttrEditor.setAsText(rolesList.toString()); return (ConfigAttributeDefinition) configAttrEditor.getValue(); } } public Collection getConfigAttributeDefinitions() { return null; } public boolean supports(Class arg0) { return true; } } This getAttributes() method above essentially returns the name of Authorities (which I call Roles) that are allowed access to the current Url. OK, so now we have setup the database based resources and now the next step is to get Spring Security to read the user details from the database. The examples that come with Spring Security 2.0 shows you how to keep a list of users and authorities in the configuration file like this: You could replace these examples with this configuration so that you can read the user details straight from the database like this: While this is a very fast and easy way to configure database based security it does mean that you have to conform to a default databases schema. By default, the requires the following tables: user, authorities, groups, group_members and group_authorities. In my case this was not going to work as my security schema it not the same as what the requires, so I was forced to change the : By adding the users-by-username-query and authorities-by-username-query properties you are able to override the default SQL statements with your own. As in ACEGI security you must make sure that the columns that your SQL statement returns is the same as what Spring Security expects. There is a another property group-authorities-by-username-query which I am not using and have therefore left it out of this example, but it works in exactly the same manner as the other two SQL statements. This feature of the has only been included in the past month or so and was not available in the pre-release versions of Spring Security. Luckily it has been added as it does make life a lot easier. You can read about this here and here. The dataSource bean instructs which database to connect to, it is not included in my configuration file as it's not specific to security. Here is an example of a dataSource bean for those who are not sure: And that is all for the configuration of Spring Security. My last task was to change my current logon screen. In ACEGI you could create your own logon by making sure that you POSTED the correctly named HTML input elements to the correct URL. While you can still do this in Spring Security 2.0, some of the names have changed. You can still call your username field j_username and your password field j_password as before. However you must set the action property of your to point to j_spring_security_check and not j_acegi_security_check. Logout Conclusion This short guide on how to configure Spring Security 2.0 with access to resources stored in a database does not come close to illustrating the host of new features that are available in Spring Security 2.0, however I think that it does show some of the most commonly used abilities of the framework and I hope that you will find it useful. One of the benefits of Spring Security 2.0 over ACEGI is the ability to write more consice configuration files, this is clearly shown when I compare my old ACEGI configration (172 lines) file to my new one (42 lines). Here is my complete securityContext.xml file: As I said in step 1, downloading Spring Security was the trickiest step of all. From there on it was plain sailing...

a frequent query and request i receive, and have had as a developer myself is: “how can i fade one image into another?”. in particular, nathan wrigley of pictureandword.com , needed a method which would fade one image into another on a mouse roll over event, and then slowly fade back once the mouse has moved of the image. image rollovers were the staple javascript nugget of the 90s, and for a lot of javascript developers i know, one of the starting points that led to their passion for the javascript language. today, rollovers are a no-brainer, whether with css or the simplest of javascript: $(function () { $('img.swap').hover(function () { this.src="images/sad.jpg"; }, function () { this.src="images/happy.jpg"; });}); today’s challenge is the rollover transition! watch the complete screencast ( alternative flash version ) (quicktime version is approx. 20mb, flash version is streaming) how to approach the problem there are a few different ways in which this problem can be solved (and i’d love to hear alternative methods via the ). here are the different approaches i’m going to go through: two image single image pure css the key to all of these techniques is how the rendered markup (i.e. what the browser finally sees) is arranged: all of which are very similar. essentially, the end image for the transition must sit absolute ly in the same position as the starting image. it’s also worth keeping in mind that the images we fade between should be the same size (height & width-wise). note: all three of these techniques have a caveat: styling the start or end image may cause the effect to break. i would recommend wrapping the image in a div or span and styling that element, as it will require less changes to the javascript. either way: it is always best to test in the targeted browsers. two image technique i should start by crediting karl swedberg who runs learning jquery . he solved nathan’s transition problem using the following technique. karl’s method starts with the two images in the markup: both the start and end images. they are contained in a div and the end image is contained in a further div with absolute positioning. it is important to note that this technique works best for absolutely position images. changing the div.fade to position: relative means the div element remains as a block element, and div will stretch the width of it’s container element (defaulting to 100%). view the working example and the source html css obviously if i had more than one fading image, i would use an id or alternative class to position the top and left css properties. .fade { position: absolute; top: 100px left: 100px } .fade div { position: absolute; top: 0; left: 0; display: none; } jquery // when the dom is ready: $(document).ready(function () { // find the div.fade elements and hook the hover event $('div.fade').hover(function() { // on hovering over, find the element we want to fade *up* var fade = $('> div', this); // if the element is currently being animated (to a fadeout)... if (fade.is(':animated')) { // ...take it's current opacity back up to 1 fade.stop().fadeto(250, 1); } else { // fade in quickly fade.fadein(250); } }, function () { // on hovering out, fade the element out var fade = $('> div', this); if (fade.is(':animated')) { fade.stop().fadeto(3000, 0); } else { // fade away slowly fade.fadeout(3000); } }); }); single image technique this takes the two image technique further. i like the idea that we should let javascript add the sugar to the markup - in that we should really only want an image tag, and using some method, know which image we want to fade to. this technique allows us to insert the image in the markup as we would if there were no transition effect, and the image can be inline, rather being positioned absolutely. we are going to use the background-image css property to specify the target image to fade to. view the working example and the source html css other than the inline background image - none is required. you can also apply the background-image using classes if you like. if we wanted to absolutely position the image, or float: right for instance, the best way to do this (if we want to keep the transition), would be to wrap it in a div and style that element. jquery using jquery, we execute the following tasks: wrap the image in a span insert a new image, whose source is the background-image of our start image position the new image so that sits directly behind the starting image bind the hover event to start the effect // create our transition as a plugin $.fn.crossfade = function () { return this.each(function () { // cache the copy of jquery(this) - the start image var $$ = $(this); // get the target from the backgroundimage + regexp var target = $$.css('backgroundimage').replace(/^url|[\(\)]/g, '')); // nice long chain: wrap img element in span $$.wrap('') // change selector to parent - i.e. newly created span .parent() // prepend a new image inside the span .prepend('') // change the selector to the newly created image .find(':first-child') // set the image to the target .attr('src', target); // position the original image $$.css({ 'position' : 'absolute', 'left' : 0, // this.offsettop aligns the image correctly inside the span 'top' : this.offsettop }); // note: the above css change requires different handling for opera and safari, // see the full plugin for this. // similar effect as single image technique, except using .animate // which will handle the fading up from the right opacity for us $$.hover(function () { $$.stop().animate({ opacity: 0 }, 250); }, function () { $$.stop().animate({ opacity: 1 }, 3000); }); }); }; // not only when the dom is ready, but when the images have finished loading, // important, but subtle difference to $(document).ready(); $(window).bind('load', function () { // run the cross fade plugin against selector $('img.fade').crossfade(); }); pure css technique if i’m honest, this final technique is a bit cheeky - but still valid. it uses css animations currently only available in safari 3 (and webkit). however, this is a great example of how to the leverage css using an iphone, in place javascript. the html is the same rendered html from the single image technique - but it requires zero javascript. html css although this is only supported in safari 3, the roll over still works in firefox (and could work in ie7 - though not ie6 because :hover only works on anchors) - because it’s changing the image’s opacity on :hover . img.fade { opacity: 1; -webkit-transition: opacity 1s linear; } img.fade:hover { opacity: 0; } taking it further i’ve taken the single image technique further in to a complete plugin. it’s designed to allows us to pass options to control the type of bind, delays, callbacks and tests before running the animation. download the full plugin you can see the plugin in action in this simple memory game i put together quickly. it pulls the latest photos from flickr , shuffles them, and then sets your memory skills to work. it’s obviously just a quick prototype - and i’m not sure what happens when you go beyond level 5! enjoy.

Last week, in part 1, Andre Mare introduced us to the Builder pattern. Today he continues his series on the "Gang of Four" design patterns. -- Geertjan Wielenga, JavaLobby Zone Leader Intent Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses. - Gof Type Class Creational Solution The Factory Method Pattern is a well known Creational Pattern that creates an abstraction through which one of several classes is returned. The pattern enables us to encapsulate the instantiation of concrete types. The pattern is classified as a Class Creational Pattern which means the pattern makes use of inheritance to decide what object to instantiate. The Factory Method Pattern consists of a Product, ConcreteProduct, Creator, ConcreteCreator and Client. The Product defines the type or interface for the concrete objects that are created by the Factory Method. The ConcreteProduct provides the implementation of the different Product types created by the Factory Method. The ConcreteProduct is instantiated by the factory method of the different ConcreteCreator objects. The Creator class specify the creator method or factory method that returns objects of type Product. The ConcreteCreator provides the concrete factory methods. These methods override the factory method in the Creator class to return the ConcreteProduct instance. The Client object is decoupled from the ConcreteProduct objects, but uses the factory method to return the appropriate ConcreteProduct through the Product type. The pattern makes use of polymorphism to decouple the client from the class created by the Factory Method. The Factory Method returns an instance of a class (ConcreteProduct) that is defined through an interface or abstract parent (Product) class. The method where the class is created returns the object through its interface or abstract parent class, so that the client is decoupled from the actual ConcreteProduct class. All the returned classes through the factory methods have the same type (interface) or abstract parent class. Structure Java Sample Code Download : Bank Account System The following example will illustrates the use of the Factory Method pattern. The Bank Account System example illustrates the creation of different bank accounts for different banks. The first diagram illustrates the different bank account types that are available. Product & ConcreteProducts The Bank Account System contains an abstract type for all the bank accounts available called the BacnkAccountProduct. The other classes are ConcreteProduct classes that is created by the Factory Method, depending on the type and the ConcreteCreator class. Creator & ConcreteCreator The BankAccountCreator or Creator class defines the factory method as abstract so that the implementation is delegated to the subclasses. The factory method is defined as follows: protected abstract BankAccountProduct createBankAccount(String accountType); This factory method is then implemented in all the different subclasses of the BankAccountCreator class. Each different ConcreteCreator knows how to instantiate the different ConcreteProduct classes. Factory Method Class Diagram The class diagram below show the dependencies between the different classes as used in the Bank Account System example. The BankSystemClient class has a gets a reference to an object of type BankAccountProduct. The client does not know what the implementing class is, but rather works through the abstract BankAccountProduct class. Sequence Diagram Sequence Diagram by "Yanic Inghelbrecht" with Trace Modeler References Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. Design Patterns: Elements of Reusable Object-Oriented Software. Addison Wesley, 1995

Two days ago, the 1.0 release of the Swing Explorer was announced. It is a handy tool for examining an application's component hierarchies, properties, events, and threads. Swing Explorer, yet another cool application available on dev.java.net, is handy when debugging your Swing application. In some ways, it is comparable to an AST Viewer, except that it displays component hierarchies instead of an abstract syntax tree. Just as an AST view is crucial when working with the internals of a language, so the Swing explorer is essential in understanding the relationships between components in a Swing application. Below is a case in point, the explorer view on the left showing the complete hierarchy of the application under observation: Of course, an IDE or GUI Builder would provide a similar view. The difference is that, in this case, the above application is deployed from a JAR outside of an IDE. In other words, the application is not in development/production mode, although it could be too. The Swing Explorer starts up your application with this command: java -javaagent:swag.jar -Xbootclasspath/a:swag.jar -cp swexpl.jar; org.swingexplorer.Launcher And that's it. Your own application then starts up, as does the Swing Explorer. Then you can explore the application in the way shown above. Not only the component hierarchy of the application is then exposed, but also all its properties, such as its layout and borders. The tabs at the bottom are very useful too. The "Player" tab lets you observe the order in which the application is constructed and the content is drawn. Some questions that you can have answered by means of the Swing Explorer: "I do not see a component on my JFrame. However, it should be there." "My colleague developed a panel two years ago. I have no idea how it is constructed. I'd like to figure out why a component appears on this place? Why it is shifted 5 pixels to the left?" "I want to debug my application in a Java debugger step by step and watch what each step produces on the screen when I add components into my JFrame." "I see a small dot in the upper right corner, why it is there?" For info on these and related usecases, see Getting Started with Swing Explorer. The "AWT Events" and the "EDT Monitor" tabs are new, providing useful information on AWT and EDT, with further finegrained filtering planned for future releases. Here's the EDT Monitor in action: The plan to provide plugins for Eclipse and NetBeans IDE is also an interesting one. Swing user interface debugging--seems like this tool is perfectly attuned to this need.

Either because you're new to them, or as a refresher, here is the start of a series on the "Gang of Four" design patterns. Andre Mare, the author of the Java Design Concepts blog, is a J2EE Specialist and has more than seven years experience in development and design of enterprise systems. Here he starts a series of articles that aim to introduce you to the "Gang of Four" design patterns. -- Geertjan Wielenga, JavaLobby Zone Leader Intent of the Pattern The Builder Pattern separates the construction of a complex object from its representation so that the same construction process can create different representations. - Gof Type Object Creational Solution The Builder Pattern simplifies the construction of complex objects by only specifying the type and content that the object requires. The construction process of the complex object will therefore allow for different representations of the complex object to be created by the different builders. Each of the concrete builder objects will construct a different representation of the complex object. The Builder Pattern consists of a Builder, ConcreteBuilder, Director and Product. The Director object is responsible for the construction process of the complex object but delegates the actual creation and assembly to the Builder interface. The Builder object specifies the interface for creating parts of the complex object. The Product represents the complex object that is created by the ConcreteBuilder objects. The Product consists of multiple parts that are created separately by the ConcreteBuilder objects. The ConcreteBuilder objects create and assemble the parts that make up the Product through the Builder interface. A client object creates an instance of the Director object and passes it the appropriate Builder object. The Director object invokes the methods on the Builder object to create and initialize specific parts of the Product object. The Builder receives content from the Director object and adds these to the Product object. The Client object has a reference to the Builder object and retrieves the created Product object from it. Structure The construction of the Complex object (Product) is hidden by the Builder objects from the Client and Director objects. To change the internal representation of the complex object, a new concrete builder object is defined and used by the client through the Director object. Unlike other creational patterns, the Builder Pattern creates the complex object is sections through the Director and Builder objects. The Builder object may need access to information that was used in previous construction steps. This means that even thought the parts of a Product object is created in individual sections; they may interact with other sections to create the complex product object. The complex Product objects do not usually have a shared abstract parent object, as their representation differ and a shared parent class or interface might not be possible. As the client object specify the Builder object, it should have the knowledge how to handle the product object that is created by the Builder object. Java Sample Code The example for the Builder Pattern is a meal that can be purchased at many fast food franchises. The complex Product is a combo meal that consists of a burger, beverage and a side order. The Builder objects are the different assistants at the till that knows how to create the combo meal for the client. The Director object is the instructions the client gives the assistant on how the specific order should be created. Example Combo Meal: Download Combo Meal Example ComboMealClient.java The ComboMealClient class makes use of the ComboMealDirector and the ComboMeal1ConcreteBuilder class to create a complex object called ComboMealProduct. Code: ComboMeal1ConcreteBuilder concreteBuilder = new ComboMeal1ConcreteBuilder(); ComboMealDirector mealDirector = new ComboMealDirector(concreteBuilder); ComboMealProduct comboMealProduct = null; mealDirector.constructComboMeal(SuperSize.HUGE); comboMealProduct = concreteBuilder.getComboMealProduct(); ComboMealDirector.java The ComboMealDirector class invokes the appropriate methods on the ConcreteBuilder (ComboMeal1ConcreteBuilder) to create a complex product ComboMealProduct. Code: public void constructComboMeal(SuperSize _mealSize) { comboMealBuilder.buildBurgerPart(); comboMealBuilder.buildSideOrderPart(_mealSize); comboMealBuilder.buildBeveragePart(_mealSize); } // method constructComboMeal ComboMealProduct.java The ComboMealProduct class is the complex object whose individual parts is created by the different Builder objects. ComboMealBuilder.java The ComboMealBuilder class contains the interface that is used by the ComboMealDirector to create the complex object. ComboMeal1ConcreteBuilder.java The ComboMeal1ConcreteBuilder class contains implementation that is used by the ComboMealDirector to create the complex object. Class Diagram Example Sequence Diagram Sequence Diagram by "Yanic Inghelbrecht" with Trace Modeler References Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. Design Patterns: Elements of Reusable Object-Oriented Software. Addison Wesley, 1995

NetBeans IDE is one of the main free Java editors in the market. In fact, it can be used to program in many other computer languages, like C/C++, Ajax, Javascript. NetBeans IDE can be extended by adding modules that add new features. So... you can have a programming editor customized to your needs. This tutorial can be of interest for all those who want to create a module that adds support for a new language inside NetBeans IDE. Original article: http://hiperia3d.blogspot.com/2008/04/netbeans-tutorial.html (the original article has coloring that makes reading easier. If you have some dificulty reading it here, you can go there). The process of creating the first of the modules that compose my X3DV Module Suite was similar to the one described here. We will learn how to make a module that has these features: Syntax highlighting that is specific for the language we will define. Brace completion and auto-indentation. Icons for the new files of that language. To be able to create new files written in our new language. Template for the new files written in that language. Just download the last version of NetBeans IDE (download NetBeans IDE 6.1 Beta). Then, follow all the steps described here. This tutorial is valid for the 6.1 version of NetBeans IDE, which has many improvements that make module building easier. This tutorial takes a fictional language called Foo Language as a sample. I suggest to follow the tutorial as it is, and later, adapt it to your needs. This is not a highly technical tutorial, but a quickstart guide that can be very easy for newcomers. First Steps With Your Module Create a new NetBeans project: Choose NetBeans Modules in Categories and Module in Projects: Fill in your project Name, locate the directory where its project folder will be placed, and mark it as a Standalone Module. Fill the info for your module. You just have to fill the two first text boxes: change the Code Name Base to what is appropriate for your module and choose a Display Name. The project will be created. Now we will add the basic: support files for the new file type. New File Type Support Over the project name, right click and select New/File Type: In the dialog that appears, you must enter some data so the NetbBeans IDE recognizes the new file type. In MIME Type you must enter text/x- usually followed by the main extension of the file type. Why does it say text/x-? As you may note, what you enter is not the true MIME type. For the IDE, all the extensions we create are text files. In Extension(s) you must enter them separated with spaces. In our example, there's only one extensions for Foo Files: .foo In Class Name Prefix, you enter the name of the file type, so all classes generated by the IDE for this module will start with it. In Icon, you must locate in your hard drive a gif icon of 16x16 pixels. In our example, it's this: Although in some tutorials they say that jpg and png images can also be used, I found that sometimes they're not displayed. So I recommend using gif images, as they are less error-prone. The IDE will copy your icon to the project directory. At this point, a bunch of files will be created by NetBeans IDE and opened in the code editor. Close them all, you don't need to edit them. Now our module is ready to recognize and create the new file types. But we want the new files to have a default content. So we will edit the generated template. Locate the file named: Edit it and write the content that you want to be the default when you create a new file. Locate the XML Layer in the module. The XML Layer file is the soul of our module. It controls most of the things that a module can do. Locate these lines: The next step is to create a description of the new supported file type that will be displayed when you want to create it, in the New File Wizard. This description will be stored in a file called "Description.html" (strange... uh?). Add this line after the one highlighted in blue, modifying it to your project url: This line we added describes where the Description of the new file is. Right click over your project and select New/Other. Select Other/HTML file. Name the file "Description", and leave the rest as it is. Replace all the contents of the generated file with this: Creates a foo file that is useful for nothing at all. This is what we will see as a result of these steps once the module is finished and we want to create a Foo file. Create the Language Support Now that we have the new files recognized, we will add syntax coloring and other features to our language module. To be able to support language features, we must do the following: right click over your project and choose "Properties". The properties of your module will be displayed. Click over libraries (on the left) and then the "Add..." button. In the list, search for the entry called "Generic Languages Framework", and add it. Now, right click over your project and select New/Other. In Categories, select "Module Development", and on the right, select "Language Support". Then enter the MIME Type and Extensions as we did in the first section of our tutorial. You will see that the XML Layer has changed and now has more things added. Between them, there's a new file that describes our language. That file is called "language.nbs". As the XML Layer has been modified, the icon of our files may have disappeared, so we need to add something to the XML Layer file to recover it. Close all the opened files. Locate the file called XML Layer, and open it. Locate the line highlighted in blue in this image, that says And replace that entire line with: Editing The Language File The default language.nbs file is filled with contents that may be a good start point for a scripting language. For declarative languages like VRML or X3D, or markup languages like HTML or similar, these contents are not useful. In our example of the Foo Language, we will use a very simple language definition. This way you will understand the basics of defining languages. So delete all the contents of the file language.nbs, and replace them with this: # To change this template, choose Tools | Templates # and open the template in the editor. # definition of tokens TOKEN:header:( "# foo language v1.0" ) TOKEN:line_comment: ( "#"[^ "\n" "\r"]* | "//"[^ "\n" "\r"]* ) TOKEN:keyword:( "foo_function" | "foo_command" ) TOKEN:field:( "foo_value" ) # all that follows is useful for mostly all languages TOKEN:identifier: ( ["a"-"z" "A"-"Z"] ["a"-"z" "A"-"Z" "0"-"9" "_"]* ) TOKEN:number: (["0"-"9"]*) TOKEN:operator: ( ":" | "*" | "?" | "+" | "-" | "[" | "]" | "<" | ">" | "^" | "|" | "{" | "}" | "(" | ")" | "," | "=" | ";" | "." | "$" ) TOKEN:string:( "\"" ( [^ "\"" "\\" "\r" "\n"] | ("\\" ["r" "n" "t" "\\" "\'" "\""]) | ("\\" "u" ["0"-"9" "a"-"f" "A"-"F"] ["0"-"9" "a"-"f" "A"-"F"] ["0"-"9" "a"-"f" "A"-"F"] ["0"-"9" "a"-"f" "A"-"F"]) )* "\"" ) TOKEN:string:( "\'" ( [^ "\'" "\\" "\r" "\n"] | ("\\" ["r" "n" "t" "\\" "\'" "\""]) | ("\\" "u" ["0"-"9" "a"-"f" "A"-"F"] ["0"-"9" "a"-"f" "A"-"F"] ["0"-"9" "a"-"f" "A"-"F"] ["0"-"9" "a"-"f" "A"-"F"]) )* "\'" ) TOKEN:whitespace:( [" " "\t" "\n" "\r"]+ ) # colors COLOR:header:{ foreground_color:"orange"; background_color:"black"; font_type:"bold"; } COLOR:line_comment:{ foreground_color:"#969696"; } COLOR:keyword:{ foreground_color:"red"; font_type:"bold"; } COLOR:field:{ foreground_color:"#25A613"; font_type:"bold"; } # parser should ignore whitespaces SKIP:whitespace # brace completion COMPLETE "{:}" COMPLETE "(:)" COMPLETE "\":\"" COMPLETE "\':\'" # brace matching BRACE "{:}" BRACE "(:)" # indentation support INDENT "{:}" INDENT "(:)" Now, create a Foo file, using a plain text editor, and save it with the extension .foo These will be its contents: # foo language v1.0 # comment // another comment foo_function { foo_command ( foo_value 1 0 1 ); } Now let's see the language.nbs file and understand the basic parts. TOKEN:header:( "# foo language v1.0" ) TOKEN:keyword:( "foo_function" | "foo_command" ) The Tokens are the words that are part of your language, and you want them colored. They define types of words that have something in common in your language. You group them into a category, that is a token. The words are between double quotes, and separated by a | sign. COLOR:header:{ foreground_color:"orange"; background_color:"black"; font_type:"bold"; } COLOR:line_comment:{ foreground_color:"#969696"; } This defines the colors used for each token. You can specify more properties for colors, but these are the basic ones. All these properties are very easy to understand by their own names, as you see. The colors can be specified by their names (although it recognizes only a few) or by its number. # brace completion COMPLETE "{:}" What these lines do is that when you type a { sign, the editor automatically will type } after your caret, speeding your work and making it less error-prone. # brace matching BRACE "{:}" # indentation support INDENT "{:}" This sentences make that when you place the caret over a brace, the matching brace will be highlighted, and that lines after those signs will be indented. Final Note Now you know all that is needed to create the basic support for a new file type and language syntax highlighting. You can add anything you like to your module, that you think is important for you and that could make your work easier. There's much more than can be done with NetBeans IDE. I invite just to test it, join its huge community of users, and experience it by yourself. -Jordi R. Cardona- X3D/VRML Worldbuilder Java Programmer X3DV Module Suite Developer. Hiperia3D News © 2008 by Jordi R. Cardona. The images and text of this post were added by the author to dzone. The author has granted dzone.com with exclusivity to use these images and text for the only purpose to spread this article. If you want to promote this tutorial, you can link to the original one at: http://hiperia3d.blogspot.com/2008/04/netbeans-tutorial.html