java - 如何使用@EntityListeners记录@Entity更改？

Question

我想创建一个记录器来记录实体上的任何 CRUD 操作。 插入或删除很容易。但是我如何在更新过程中访问以前的实体，以便我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，并检查 PreUpdate 方法中的差异

// 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();
}

}