更新JPA实体中的一个字段 [英] Updating one field in JPA entity

问题描述

我有一个实体User，该实体在功能中分配了系统特权.我有一个网页，您可以在其中从下拉列表中选择一个用户，然后将表单提交到服务器.在服务器端，我只想为该实体更新一个字段.

I have an Entity User that is assigned a system privilege in a function. I have a web page where you select a user from a drop down and submit the form to the server. On the server side I want to update only one field for that entity.

我的用户"实体将对所有对象具有默认值，但要设置的一个字段及其ID除外.我需要做一个findById然后更新特定的字段然后进行合并吗?或者有没有办法告诉该用户只更新那个字段?

My User entity will have default values for all objects except the one field that gets set and its id. Do I need to do a findById then update the specific field then do the merge or is there a way to tell the to only update that field?

推荐答案

我需要执行一次findById，然后更新特定字段，然后进行合并

Do I need to do a findById then update the specific field then do the merge

这是常规方法，只是不需要合并托管实体，只需让JPA检测到更改并自动更新即可.

That would be the regular approach, except that you don't need to merge a managed entity, just let JPA detect the changes and update it automatically.

还是有一种方法告诉只能更新该字段?

or is there a way to tell the to only update that field?

不.但是您可以使用User的简短"版本(仅更新字段).另一个选择是使用批量更新操作，但这不是IMO真正的好用例.我不会使用这种方法.

No. But you could use a "short" version of your User (with only the field(s) to update). Another option would be to use a Bulk Update Operation but this is IMO really not a good use case. I wouldn't use this approach.

• JPA 1.0规范
  • 4.10批量更新和删除操作
  • JPA 1.0 specification
    • 4.10 Bulk Update and Delete Operations

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