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POHow to intercept methods of EntityManager with Seam 3?
 

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  1. POHow to intercept methods of EntityManager with Seam 3?
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    <p>I'm trying to intercept the method <code>persist</code> and <code>update</code> of <code>javax.persistence.EntityManager</code> in a <strong>Seam 3</strong> project.</p> <p>In a previous version (Seam 2) of the micro-framework I'm trying to make, I did this using an implementation of <code>org.hibernate.Interceptor</code> and declaring it in the <code>persistence.xml</code>.</p> <p>But I want something more "CDI-like" now we are in a JEE6 environment.</p> <p>I want that just before entering in a <code>EntityManager.persist</code> call, an event <code>@BeforeTrackablePersist</code> is thrown. The same way, I want an event <code>@BeforeTrackableUpdate</code> to be thrown before entering in a <code>EntityManager.merge</code> call. <code>Trackable</code> is an interface which some of my <code>Entity</code>s could implement in order to be intercepted before persist or merge.</p> <p>I'm using Seam 3 (3.1.0.Beta3) Extended Persistence Manager :</p> <pre class="lang-java prettyprint-override"><code>public class EntityManagerHandler { @SuppressWarnings("unused") @ExtensionManaged @Produces @PersistenceUnit private EntityManagerFactory entityManagerFactory; } </code></pre> <p>So I've made a <code>javax.enterprise.inject.spi.Extension</code>, and tryied many ways to do that :</p> <pre class="lang-java prettyprint-override"><code>public class TrackableExtension implements Extension { @Inject @BeforeTrackablePersisted private Event&lt;Trackable&gt; beforeTrackablePersistedEvent; @Inject @BeforeTrackableMerged private Event&lt;Trackable&gt; beforeTrackableMergedEvent; @SuppressWarnings("unchecked") public void processEntityManagerTarget(@Observes final ProcessInjectionTarget&lt;EntityManager&gt; event) { final InjectionTarget&lt;EntityManager&gt; injectionTarget = event.getInjectionTarget(); final InjectionTarget&lt;EntityManager&gt; injectionTargetProxy = (InjectionTarget&lt;EntityManager&gt;) Proxy.newProxyInstance(event.getClass().getClassLoader(), new Class[] {InjectionTarget.class}, new InvocationHandler() { @Override public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable { if ("produce".equals(method.getName())) { final CreationalContext&lt;EntityManager&gt; ctx = (CreationalContext&lt;EntityManager&gt;) args[0]; final EntityManager entityManager = decorateEntityManager(injectionTarget, ctx); return entityManager; } else { return method.invoke(injectionTarget, args); } } }); event.setInjectionTarget(injectionTargetProxy); } public void processEntityManagerType(@Observes final ProcessAnnotatedType&lt;EntityManager&gt; event) { final AnnotatedType&lt;EntityManager&gt; type = event.getAnnotatedType(); final AnnotatedTypeBuilder&lt;EntityManager&gt; builder = new AnnotatedTypeBuilder&lt;EntityManager&gt;().readFromType(type); for (final AnnotatedMethod&lt;? super EntityManager&gt; method : type.getMethods()) { final String name = method.getJavaMember().getName(); if (StringUtils.equals(name, "persist") || StringUtils.equals(name, "merge")) { builder.addToMethod(method, TrackableInterceptorBindingLiteral.INSTANCE); } } event.setAnnotatedType(builder.create()); } public void processEntityManagerBean(@Observes final ProcessBean&lt;EntityManager&gt; event) { final AnnotatedType&lt;EntityManager&gt; annotatedType = (AnnotatedType&lt;EntityManager&gt;)event.getAnnotated(); // not even called } public void processEntityManager(@Observes final ProcessProducer&lt;?, EntityManager&gt; processProducer) { processProducer.setProducer(decorate(processProducer.getProducer())); } private Producer&lt;EntityManager&gt; decorate(final Producer&lt;EntityManager&gt; producer) { return new Producer&lt;EntityManager&gt;() { @Override public EntityManager produce(final CreationalContext&lt;EntityManager&gt; ctx) { return decorateEntityManager(producer, ctx); } @Override public Set&lt;InjectionPoint&gt; getInjectionPoints() { return producer.getInjectionPoints(); } @Override public void dispose(final EntityManager instance) { producer.dispose(instance); } }; } private EntityManager decorateEntityManager(final Producer&lt;EntityManager&gt; producer, final CreationalContext&lt;EntityManager&gt; ctx) { final EntityManager entityManager = producer.produce(ctx); return (EntityManager) Proxy.newProxyInstance(entityManager.getClass().getClassLoader(), new Class[] {EntityManager.class}, new InvocationHandler() { @Override public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable { final String methodName = method.getName(); if (StringUtils.equals(methodName, "persist")) { fireEventIfTrackable(beforeTrackablePersistedEvent, args[0]); } else if (StringUtils.equals(methodName, "merge")) { fireEventIfTrackable(beforeTrackableMergedEvent, args[0]); } return method.invoke(entityManager, args); } private void fireEventIfTrackable(final Event&lt;Trackable&gt; event, final Object entity) { if (entity instanceof Trackable) { event.fire(Reflections.&lt;Trackable&gt;cast(entity)); } } }); } } </code></pre> <p>In all those observer methods, only the second one (<code>processEntityManagerType(@Observes ProcessAnnotatedType&lt;EntityManager&gt;)</code>) is called ! And even with that binding addition to methods <code>persist</code> and <code>merge</code>, my Interceptor is never called (I've of course enabled it with the correct lines in <code>beans.xml</code>, and enabled my extension with the <code>services/javax.enterprise.inject.spi.Extension</code> file).</p> <p>Something I've thought simple with CDI seems to be actually really hard at last... or perhaps Seam 3 does something which prevent this code from executing correctly...</p> <p>Does someone know how to handle that ?</p>
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    1. USAnthony O.
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    1. COI've opened a feature request at Seam Persistence module : https://issues.jboss.org/browse/SEAMPERSIST-75
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      1. USAnthony O.
 

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