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The Local / Remote interfaces in EJB 3.1 are optional. You can still, however, expose a Session bean as a RESTFul (JSR-311) service.

package com.abien.patterns.business.rest.boundary;

import com.abien.patterns.business.rest.control.Service;
import javax.ejb.EJB;
import javax.ejb.Stateless;
import javax.ws.rs.GET;
import javax.ws.rs.Path;

@Stateless
@Path("current")
public class ServiceFacade {

    @EJB
    Service service;

    @GET
    public String getDate(){
        return service.getCurrentDate().toString();
    }

}

The Service is just another, usual, @Local bean:

@Stateless
public class Service {

    public Date getCurrentDate(){
        return new Date();
    }
}

A ServiceFacade becomes available via REST, just denoting it with the JAR-RS annotations. Its both an EJB 3.1 and a REST-resource - it is available under http://localhost:8080/EJBRestHybrid/resources/current (tested with Glassfish v3 preview). It will return the current time as String (Mon Jun 29 08:19:32 CEST 2009). The additional @Stateless has the following advantages:

• Injection capabilities: you can easily inject other EJBs, EntityManagers, JMS-resources, DataSources or JCA connectors
• Transactions: all changes made in a REST-call will be automatically and transparently synchronized with the database
• Single threading programming model -> the old EJB goodness.
• Monitoring: an EJB is visible in JMX
• Throttling: its easy to restrict the concurrency of an EJB using ThreadPools or bean pools
• Vendor-independence: EJB 3 runs on multiple containers, without any modification (and without any XML in particular :-))

Posted at 09:05AM Jun 29, 2009 by Adam Bien in Real World Java EE Patterns - Rethinking Best Practices  |  Kommentare[2]

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