如何使用@EntityListeners记录@EntityListeners的更改？

Question

我想创建一个记录器来记录实体上的任何CRUD操作。这在insert或delete上很容易。但是我如何在update过程中访问之前的实体，这样我就可以记录更改的字段(例如通过反射访问)。

@Entity
@EntityListeners(AuditingEntityListener.class)
public class MyEntity {
}

public class AuditEntityListener {
    private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());
    private static final Marker AUDIT = MarkerFactory.getMarker("AUDIT");

    @PrePersist
    public void prePersist(Object target) {
        log("new object inserted", target);
    }

    @PreRemove
    public void preRemove(Object target) {
        log("entity deleted", target);
    }

    @PreUpdate
    public void preUpdate(Object target) {
        //TODO how can I access the "old" entity, so that I can log only changed fields (eg via reflection)?
    }
}

Answer 1

您可以将previousState保存在PostLoad方法中，并在PreUpdate方法中检查差异

// EDIT
@Entity
@EntityListeners(AuditingEntityListener.class)
public class MyEntity {
   @Transient
   private transient MyEntity savedState;

}

public class AuditEntityListener {
    private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());
    private static final Marker AUDIT = MarkerFactory.getMarker("AUDIT");

@PostLoad
 private void saveState(MyEntity target){

    target.savedState = SerializationUtils.clone(target);
 }

@PrePersist
public void prePersist(MyEntity target) {
    log("new object inserted", target);
}

@PreRemove
public void preRemove(MyEntity target) {
    log("entity deleted", target);
}

@PreUpdate
public void preUpdate(MyEntity target) {
    MyEntity previousState = target.getSavedState();
}

}

Answer 2

尝试查看Hibernate的事件SPI。Hibernate Envers实现了一些提供的SPI。我目前使用的是Hibernate 5。

实现org.hibernate.event.spi.PostUpdateEventListener接口，该接口将重写public void onPostUpdate(PostUpdateEvent event)。PostUpdateEvent可以让你访问一些有用的东西，例如PostUpdateEvent#getOldState()。

完成后，您需要将该侦听器注册到SPI集成器。实施org.hibernate.integrator.spi.Integrator。

// Overriden public void integrate(Metadata metadata, SessionFactoryImplementor sessionFactory,
//                          SessionFactoryServiceRegistry serviceRegistry)
        final EventListenerRegistry eventListenerRegistry = serviceRegistry.getService(EventListenerRegistry.class);

        eventListenerRegistry.appendListeners(EventType.POST_UPDATE, YourListener.INSTANCE);

然后通过创建META-INF/services/org.hibernate.integrator.spi.Integrator在应用程序中注册该集成器。在这个文件中，您需要输入已实现的Hibernate Integrator的类名。示例：

com.company.my.ImplementedHibernateIntegrator

其他版本的Hibernate可能有不同的方法，例如https://vladmihalcea.com/hibernate-event-listeners/