DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Refcards Trend Reports Events Over 2 million developers have joined DZone. Join Today! Thanks for visiting DZone today,
Edit Profile Manage Email Subscriptions Moderation Admin Console How to Post to DZone Article Submission Guidelines
View Profile
Sign Out
Refcards
Trend Reports
Events
Zones
Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Partner Zones AWS Cloud
by AWS Developer Relations
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Partner Zones
AWS Cloud
by AWS Developer Relations
  1. DZone
  2. Coding
  3. Java
  4. Java EE6 Events, a lightweight alternative to JMS

Java EE6 Events, a lightweight alternative to JMS

Jelle Victoor user avatar by
Jelle Victoor
·
Jun. 22, 11 · Interview
Like (2)
Save
Tweet
Share
19.41K Views

Join the DZone community and get the full member experience.

Join For Free

A few weeks ago I attended a bejug meeting about Java EE 6, Building next generation enterprise applications. Having read much about it, I did not expect to see much shocking hidden features. But there was one part of the demo I really found impressive. Due to its loose coupling, Enterprise possibilities and simplicity. The feature I’m going to talk about today is the event mechanism that is in java EE 6.
The general idea is to fire an event and let an eventlistener pick it up. I have created this example that is totally useless, but it simplicity helps me to focus on the important stuff. I’m going to fire a LogEvent from my backing action, that will log to the java.util.Logger.
The first thing I need is to create a pojo that contains my log message and my LogLevel.

public class LogMessage implements Serializable {
 
    private final String message;
    private final Level level;
 
    LogMessage(String message, Level level) {
        this.message = message;
        this.level = level;
    }
 
    public String getMessage() {
        return message;
    }
 
    public Level getLevel() {
        return level;
    }
}

easy peasy.
Now that I have my data wrapper, I need something to fire the event and something to pick it up. The first thing I create is my method where I fire the event.
Due to CDI I can inject an event.

@Inject Event<LogMessage> event;

So we just need to fire it.

event.fire(new LogMessage("Log it baby!", Level.INFO));

Now the event is fired, If no one is registerd to pick it up, it disappears into oblivion, thus we create a listener. The listeners needs a method that has one parameter, the generic type that is given to the previous event. LogMessage.

public class LogListener {
    private static final Logger LOGGER = Logger.getAnonymousLogger();
    public void process(@Observes LogMessage message){
        LOGGER.log(message.getLevel(), message.getMessage());
    }
}

The @Observes annotation listens to all events with a LogMessage. When the event is fired, this method will be triggered.
This is a very nice way to create a loosely coupled application, you can separate heavy operations or encapsulate less essential operations in these event listeners.
All of this all happens synchronously. When we want to replace the log statement with a slow database call to a logging table, we could make our operation heavier than it should be. What I’m looking for is to create an asynchronous call.
As long as we support EJB, we can transform our Listener to an EJB by adding the @Stateless annotation on top of it. Now it’s a statless enterprise bean. This changes nothing to our sync/async problem, but EJB 3.1 support async operations. So if we also add the @Asynchronous annotation on top of it. It will asynchronously execute our logging statement.

@Stateless
@Asynchronous
public class LogListener {
    private static final Logger LOGGER = Logger.getAnonymousLogger();
    public void process(@Observes LogMessage message){
        LOGGER.log(message.getLevel(), message.getMessage());
    }
}

If we would want to combine the database logging and the console logging, we can just create multiple methods that listen to the same event.
This is a great way to create a lightweight application with a very flexible components. The alternative solution to this problem is to use JMS, but you don’t want a heavyweight configuration for this kind of loosely coupling.
Java EE has worked hard to get rid of the stigma of being heavyweight, I think they are getting there :-)

 

From http://styledideas.be/blog/2011/05/22/java-ee6-events-a-lightweight-alternative-to-jms/

Event Java (programming language)

Opinions expressed by DZone contributors are their own.

Popular on DZone

  • OWASP Kubernetes Top 10
  • Secure APIs: Best Practices and Measures
  • 5 Software Developer Competencies: How To Recognize a Good Programmer
  • Java REST API Frameworks

Comments

Partner Resources

X

ABOUT US

  • About DZone
  • Send feedback
  • Careers
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 600 Park Offices Drive
  • Suite 300
  • Durham, NC 27709
  • support@dzone.com
  • +1 (919) 678-0300

Let's be friends: