休眠+"ON DUPLICATE KEY"；逻辑 [英] Hibernate + "ON DUPLICATE KEY" logic

问题描述

我正在根据表的唯一键(由几列组成)寻找保存或更新记录的方法.

I am looking for a way to save or update records, according to the table's unique key which is composed of several columns).

我想实现与INSERT ... ON DUPLICATE KEY UPDATE相同的功能-意味着盲目保存一条记录，并让DB/Hibernate插入一条新记录，或者如果唯一键已经存在，则更新现有记录.

I want to achieve the same functionality used by INSERT ... ON DUPLICATE KEY UPDATE - meaning to blindly save a record, and have the DB/Hibernate insert a new one, or update the existing one if the unique key already exists.

我知道我可以使用@SQLInsert( sql="INSERT INTO .. ON DUPLICATE KEY UPDATE")，但是我希望不要编写自己的SQL，而让Hibernate完成这项工作. (我假设它将做得更好-否则为什么要使用Hibernate?)

I know I can use @SQLInsert( sql="INSERT INTO .. ON DUPLICATE KEY UPDATE"), but I was hoping not to write my own SQLs and let Hibernate do the job. (I am assuming it will do a better job - otherwise why use Hibernate?)

推荐答案

对我来说，这听起来并不像是一种干净的方法.最好先查看具有给定密钥的实体是否存在.如果是这样，请对其进行更新并保存，否则请创建一个新的.

This doesn't really sound like a clean approach to me. It would be better to first see if an entity with given key(s) exists. If so, update it and save it, if not create a new one.

编辑

或者考虑是否要使用merge():

Or maybe consider if merge() is what you're looking for:

• 如果当前与会话相关联的持久性实例具有相同的标识符，则将给定对象的状态复制到持久性实例上
• 如果当前没有与该会话关联的持久性实例，请尝试从数据库中加载它，或创建一个新的持久性实例
• 返回持久实例
• 给定实例未与会话关联，它保持分离

< http://docs.jboss.org/hibernate/core/3.3/reference/zh-CN/html/objectstate.html

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