4.0版本改变了事件监听器注册的方式，以利用一些新增的功能，即服务和集成器。我不会过多地涉及服务，因为它们在其他地方已有说明。但让我们先从集成器的概念开始。

集成器合约

具体来说，我们谈论的是org.hibernate.integrator.spi.Integrator接口。org.hibernate.integrator.spi.Integrator的目的是提供一个简单的手段，允许开发者钩入构建功能SessionFactory的过程。Hibernate提供的一个标准服务是利用Java的java.util.ServiceLoader机制来发现org.hibernate.integrator.spi.Integrator实现。开发者只需定义一个名为/META-INF/services/org.hibernate.integrator.spi.Integrator的文件，并将其放在类路径上。本质上，这个文件的内容是一个或多个完全限定的org.hibernate.integrator.spi.Integrator实现类名，每个类名一行。有关此文件内容允许的语法的完整规范，请参阅java.util.ServiceLoader的Java文档。

org.hibernate.integrator.spi.Integrator接口定义了两个感兴趣的方法

public interface Integrator {
    /**
     * Perform integration.
     *
     * @param configuration The configuration used to create the session factory
     * @param sessionFactory The session factory being created
     * @param serviceRegistry The session factory's service registry
     */
    public void integrate(Configuration configuration, SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry);

    /**
     * Tongue-in-cheek name for a shutdown callback.
     *
     * @param sessionFactory The session factory being closed.
     * @param serviceRegistry That session factory's service registry
     */
    public void disintegrate(SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry);

    /** 
     * Ignore this form!  Just do nothing in impl.  It uses the new metamodel api slated for completion in 5.0
     */
    public void integrate(MetadataImplementor metadata, SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry );
}

integrate方法允许我们钩入构建过程；disintegrate允许我们钩入SessionFactory的关闭。

注册

Hibernate本身有几个org.hibernate.integrator.spi.Integrator接口的实现，它们执行事件监听器注册，可以参考。

• https://github.com/hibernate/hibernate-orm/blob/master/hibernate-envers/src/main/java/org/hibernate/envers/event/EnversIntegrator.java
• https://github.com/hibernate/hibernate-orm/blob/master/hibernate-entitymanager/src/main/java/org/hibernate/ejb/event/JpaIntegrator.java

注册监听器的一般过程如下

    public void integrate(Configuration configuration, SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry) {
        // As you might expect, an EventListenerRegistry is the place with which event listeners are registered  It is a service
        // so we look it up using the service registry
        final EventListenerRegistry eventListenerRegistry = serviceRegistry.getService( EventListenerRegistry.class );

        // If you wish to have custom determination and handling of "duplicate" listeners, you would have to add an implementation
        // of the org.hibernate.event.service.spi.DuplicationStrategy contract like this
        eventListenerRegistry.addDuplicationStrategy( myDuplicationStrategy );

        // EventListenerRegistry defines 3 ways to register listeners:
        //     1) This form overrides any existing registrations with 
        eventListenerRegistry.setListeners( EventType.AUTO_FLUSH, myCompleteSetOfListeners );
        //     2) This form adds the specified listener(s) to the beginning of the listener chain
        eventListenerRegistry.prependListeners( EventType.AUTO_FLUSH, myListenersToBeCalledFirst );
        //     3) This form adds the specified listener(s) to the end of the listener chain
        eventListenerRegistry.appendListeners( EventType.AUTO_FLUSH, myListenersToBeCalledLast );
    }