使用場景

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

它的意義

對實體屬性變化的跟蹤，它提供了儲存前，儲存後，更新前，更新後，刪除前，刪除後等狀態，就像是攔截器一樣，你可以在攔截方法裡重寫你的個性化邏輯。

它的使用

定義介面，如實體追蹤

/**
 * 資料建立與更新.
 */
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);

}
 

定義跟蹤器

@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之後的操作");
  }

  @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之後的操作");
  }

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

  }

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

  }
}
 

實體去實現這個對應的跟蹤介面

@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;
  }
}
 

上面程式碼將實現在實體儲存時對createTime，lastUpdateTime進行賦值，當實體進行更新時對lastUpdateTime進行重新賦值的操作。