Spring Data:何时使用Projection接口和DTO投影?

问题描述

我有这种情况:

它将与Spring Data一起使用，并与@Entity

It about to work with Spring Data and working with a specific set of fields of an @Entity

这两个建议对我完全有效:

The two suggestions are totally valid for me:

1. DTO projections
2. Projection interfaces

1. DTO projections
2. Projection interfaces

更甚者，在spring-data-examples中两者同时出现(出于示例目的，我知道):

Even more, in spring-data-examples appears both together (I know for sample purposes):

• CustomerRepository.java

因此:

1. 何时必须强制使用另一种，为什么?
2. 彼此之间存在绩效成本吗?

基于类的投影(DTO)部分说明以下内容:

Note in the Class-based Projections (DTOs) section says the following:

似乎优点是:except that no proxying happens 和 no nested projections can be applied

推荐答案

DTO方法

Pro

• 简单而向前

Con

• 这将导致更多代码，因为您必须使用构造函数和getter/setter方法创建DTO类(除非您使用Project Lombok避免样板DTO的代码).

• It will result in more code as you have to create DTO class with constructor and getters/setters (unless you utilize Project Lombok to avoid boilerplatecode for DTOs).

不能应用任何嵌套投影.

No nested projections can be applied.

投影

Pro

• 由于仅使用接口而减少了代码.

• Less code as it uses only interfaces.

可以应用嵌套投影

动态投影使您可以编写一种通用存储库方法以返回根据客户的需求，实体对象中属性的不同子集.

Dynamic projection allows you write one generic repository method to returndifferent subset of the attributes in entity object based on client's needs.

Con

• Spring在运行时生成代理
尽管经过修剪的版本(通过Projection)从Spring层返回到客户端，但
• 查询可以将整个实体对象从数据库返回到Spring层.我不确定这个特定的缺点，希望有人在必要时编辑此答案.

• Spring generates proxy at runtime
• Query could return the entire entity object from database to Spring layer though a trimmed version (via Projection) is returned from Spring layer to client. I wasn't sure about this specific disadvantage, hoping someone to edit this answer if necessary.

如果您需要嵌套或动态投影，则可能需要使用Projection方法而不是DTO方法.

If you need nested or dynamic projection, you probably want Projection approach rather than DTO approach.

请参阅官方Spring文档有关详细信息.

这篇关于Spring Data:何时使用Projection接口和DTO投影?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！