JPA中EntityListeners注解的使用

使用场景

EntityListeners在jpa中使用，如果你是mybatis是不可以用的

它的意义

对实体属性变化的跟踪，它提供了保存前，保存后，更新前，更新后，删除前，删除后等状态，就像是拦截器一样，你可以在拦截方法里重写你的个性化逻辑。

它的使用

定义接口，如实体追踪

/**
 * 数据建立与更新.
 */
public interface DataEntity {

  Timestamp getDateCreated();

  void setDateCreated(Timestamp dateCreated);

  Timestamp getLastUpdated();

  void setLastUpdated(Timestamp lastUpdated);

  Long getDateCreatedOn();

  void setDateCreatedOn(Long dateCreatedOn);

  Long getLastUpdatedOn();

  void setLastUpdatedOn(Long lastUpdatedOn);

}

定义跟踪器

@Slf4j
@Component
@Transactional
public class DataEntityListener {
  @PrePersist
  public void prePersist(DataEntity object)
      throws IllegalArgumentException, IllegalAccessException {
    Timestamp now = Timestamp.from(Instant.now());
    object.setDateCreated(now);
    object.setLastUpdated(now);
    logger.debug("save之前的操作");
  }

  @PostPersist
  public void postpersist(DataEntity object)
      throws IllegalArgumentException, IllegalAccessException {

    logger.debug("save之后的操作");
  }

  @PreUpdate
  public void preUpdate(DataEntity object)
      throws IllegalArgumentException, IllegalAccessException {
    Timestamp now = Timestamp.from(Instant.now());
    object.setLastUpdated(now);
    logger.debug("update之前的操作");
  }

  @PostUpdate
  public void postUpdate(DataEntity object)
      throws IllegalArgumentException, IllegalAccessException {
    logger.debug("update之后的操作");
  }

  @PreRemove
  public void preRemove(DataEntity object) {
    logger.debug("del之前的操作");

  }

  @PostRemove
  public void postRemove(DataEntity object) {
    logger.debug("del之后的操作");

  }
}

实体去实现这个对应的跟踪接口

@EntityListeners(DataEntityListener.class)
public class Product implements DataEntity {
     @Override
  public Timestamp getDateCreated() {
    return createTime;
  }

  @Override
  public void setDateCreated(Timestamp dateCreated) {
    createTime = dateCreated;
  }

  @Override
  public Timestamp getLastUpdated() {
    return lastUpdateTime;
  }

  @Override
  public void setLastUpdated(Timestamp lastUpdated) {
    this.lastUpdateTime = lastUpdated;
  }

  @Override
  public Long getDateCreatedOn() {
    return createOn;
  }

  @Override
  public void setDateCreatedOn(Long dateCreatedOn) {
    createOn = dateCreatedOn;
  }

  @Override
  public Long getLastUpdatedOn() {
    return lastUpdateOn;
  }

  @Override
  public void setLastUpdatedOn(Long lastUpdatedOn) {
    this.lastUpdateOn = lastUpdatedOn;
  }
}

上面代码将实现在实体保存时对createTime，lastUpdateTime进行赋值，当实体进行更新时对lastUpdateTime进行重新赋值的操作。

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