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This article mainly explains "how to implement the Hibernate event system". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to implement the Hibernate event system.

We all know that it is useful for an application to be able to respond to specific events generated within the Hibernate. This allows some common functionality to be implemented as well as extensions to Hibernate events.

If you need to respond to some special Hibernate events in the persistence layer, you can also use the Hibernate event framework. The event system can be used as an alternative to or as a supplement to the interceptor.

Basically, every method of the Session interface has a corresponding Hibernate event. Such as LoadEvent,FlushEvent, etc. (check the DTD of the XML configuration file, as well as the org.hibernate.event package for a list of all defined events).

When a method is called, Hibernate Session generates a corresponding event and activates all configured event listeners.

The process implemented by the system's default listener is what the listener method does (what the listener does is actually activate the listener, and the "actual" work is done by the listener).

However, you are free to implement a custom listener (for example, implement and register the LoadEventListener interface that handles LoadEvent) to handle all requests that call the load () method of Session.

Listeners should be treated as singleton objects, that is, all processing of events of the same type share the same listener instance, so listeners should not save any state (that is, member variables should not be used).

User-customized listeners should implement an interface corresponding to the event to be handled, or inherit from an appropriate base class (or even from the default event listener class that comes with Hibernate, which is declared as non-final for your convenience).

User-customized listeners can be registered programmatically using the Configuration object or declared in Hibernate's XML-formatted configuration file (Properties-formatted configuration file declaration listeners are not supported).

Here is a listener for a user-customized load event (load event):

Public class MyLoadListener extends DefaultLoadEventListener {/ / this is the single method defined by the LoadEventListener interface public Object onLoad (LoadEvent event, LoadEventListener.LoadType loadType) throws HibernateException {if (! MySecurity.isAuthorized (event.getEntityClassName (), event.getEntityId () {throw MySecurityException ("Unauthorized access");} return super.onLoad (event, loadType);}}

You also need to modify a configuration to tell Hibernate to use the selected listener instead of the default listener.

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Let's see how to register it programmatically in another way.

Configuration cfg = new Configuration () cfg.getSessionEventListenerConfig () .setLoadEventListener (new MyLoadListener ())

Listeners registered by declaring in the XML configuration file cannot share instances. If the same class name is used in multiple nodes, each reference will produce a separate instance. If you need to share listener instances among multiple listener types, you must register programmatically.

Why do we implement the interface for a specific listener and specify which event listener we want to register when registering?

This is because a class may implement interfaces for multiple listeners. You can make it easier to configure to enable or disable listening for an event by explicitly specifying the events to listen for when registering.

At this point, I believe you have a deeper understanding of "how to implement the Hibernate event system". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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