4 Replies Latest reply on Jun 5, 2009 1:06 AM by tarciosaraiva

    Home Objects & EJB3 Interceptors

    tarciosaraiva
    tarciosaraiva Jun 4, 2009 6:40 AM

      Hi all. I'm starting to use Seam but am a bit lost - or what I'm trying to do is simply not achievable.


      Well, the background scenario is: I've just created a new Seam application on Eclipse. Then, created a few entities and Seam Actions.
      That all works fine and I believe I got what an EntityHome is: a simple object to easy our life on persistence.


      Anyway, as I said, I can insert, update and remove. It works beautifully.


      However, I would like to add an interceptor: when I say interceptor is the EJB3-like interceptor, using the @Interceptors(Clazz.class) annotation, etc; so I can register some information before the actual persistence on the database.


      Well, I was reading through the documentation and got into the stage my code is at the moment.


      Here's my class to be intercepted:



      package com.metrofile.metroasset.session;

import javax.interceptor.Interceptors;

import org.jboss.seam.annotations.Begin;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.web.RequestParameter;
import org.jboss.seam.ejb.SeamInterceptor;
import org.jboss.seam.framework.EntityHome;

import com.metrofile.metroasset.entity.Location;
import com.metrofile.metroasset.interceptors.LocationChange;

@Name("locationHome")
@LocationChange
@Interceptors(SeamInterceptor.class)
public class LocationHome extends EntityHome<Location> {

     private static final long serialVersionUID = 260787915456177497L;

     @RequestParameter
     Long locationId;

     @Override
     public Object getId() {
          if (locationId == null) {
               return super.getId();
          } else {
               return locationId;
          }
     }

     @Override
     @Begin
     public void create() {
          super.create();
     }

}





      Here's my Interceptor:



      package com.metrofile.metroasset.interceptors;

import javax.interceptor.AroundInvoke;
import javax.interceptor.InvocationContext;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.jboss.seam.annotations.intercept.Interceptor;

import com.metrofile.metroasset.entity.LocationLog;

@Interceptor
public class LocationChangeInterceptor {

     @PersistenceContext(unitName = "metroAsset")
     private EntityManager em;

     @AroundInvoke
     public Object addModificationHistory(InvocationContext invocation)
               throws Exception {

          LocationLog log = new LocationLog();
          log.setDescription(invocation.getMethod().toString());

          try {
               em.persist(log);
               em.flush();
          } catch (Exception e) {
               e.printStackTrace();
               System.out.println(e.getMessage());
          }

          return invocation.proceed();
     }

}





      And finally the annotation (as explained at the documentation):



      package com.metrofile.metroasset.interceptors;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;

import javax.interceptor.Interceptors;

/**
 * @author <a href="mailto:support@metrofile.com.au">Tarcio Saraiva</a>
 * @version 04/06/2009
 */
@Target( { ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Interceptors(LocationChangeInterceptor.class)
public @interface LocationChange {

}




      The main issue is that the EntityManager on the interceptor LocationChangeInterceptor is always null. Doesn't matter what I change - and tags I use - it's always null.


      Am I missing something? Is that the right way to use it?


      Thank you for your answers in advance - slowly I'm building up my Seam knowledge (great framework!)