JPA (Hibernate) and Setup Entity Listener on Runtime

Question

I have two projects:

• beans.jar with JPA entities (annotated for JSON/XML serialization) and persistence.xml file
• rest.war with REST application, where are JPA EntityManagerFactory instantiated with customized properties such as hibernate.connection.*

I want to distribute beans.jar for better client side programming convenience. So far good.

Some entities have code in @PrePersist event (salting password hash in fact), which I don't want to distribute. I can push that code to JPA entity listener, but listener class is referenced in @EntityListeners annotation and therefor must be in beans.jar as well.

Is it possible to setup JPA entity listener for one (or all) entity classes on runtime, i.e. in rest.war project?

Maybe there are some Hibernate property for this, which I overlooked... Thanks.

Answer 1

This sets up a generic EntityListener for all Entities.

Create a file named orm.xml and put it in the same directory as the persistence.xml file (e.g. META-INF). I am not sure if this can be put in the war file. The contents of the orm.xml file should be the following:

<?xml version="1.0" encoding="UTF-8"?>
<entity-mappings version="2.0" xmlns="http://java.sun.com/xml/ns/persistence/orm" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_2_0.xsd">
   <persistence-unit-metadata>
      <persistence-unit-defaults>
         <entity-listeners>
            <entity-listener class="nathan.db.Listener"/>
         </entity-listeners>
      </persistence-unit-defaults>
   </persistence-unit-metadata>
</entity-mappings>

Then create a class called Listener.

package nathan.db;

import javax.persistence.PrePersist;

public class Listener
{
   @PrePersist
   public void event(Object entity)
   {
      // salt password
   }
}