java - 休息资源 : get id of subentity without extra request

Question

我有这样的实体:

@Entity
class MyEntity {
    Long id;
    SecondEntity second;
    ...
}

@Entity
class SecondEntity {
    Long id;
    ...
}

我使用@RestResource作为rest-API。如果我请求 MyEntity 列表，我会得到如下结果:

{
    "_links": {
      "self": {"href": "http://localhost:8080/api/MyEntity/1"},
      "second": {"href": "http://localhost:8080/api/MyEntity/1/second"}
    }
},
{
    "_links": {
      "self": {"href": "http://localhost:8080/api/MyEntity/2"},
      "second": {"href": "http://localhost:8080/api/MyEntity/2/second"}
    }
}

如果我想检查，是[0].second == [1].second，我需要做两个额外的请求。这不太好。

也许可以配置 RestResource 来提供以下资源？

{
    "_links": {
      "self": {"href": "http://localhost:8080/api/MyEntity/1"},
      "second": {"href": "http://localhost:8080/api/SecondEntity/12"}
    }
},
{
    "_links": {
      "self": {"href": "http://localhost:8080/api/MyEntity/2"},
      "second": {"href": "http://localhost:8080/api/SecondEntity/45"}
    }
}

Answer 1

您可以使用 Spring Data REST 的投影功能来做到这一点

这里有一个解释https://spring.io/blog/2014/05/21/what-s-new-in-spring-data-dijkstra#user-content-projections-in-spring-data-rest

这是一个类似的问题How to return representations of associations in a Spring Data REST resource?