使集合属性呈现为关系而不是 json HAL 表示中的属性 [英] Make collection propertie render as relation instead of property in json HAL representaion

问题描述

我得到了 hal 格式的响应:

I got hal formatted response as this:

{
  "name": "Publisher A",
  "bookPublishers": [
    {
      "publishedDate": "2019-07-12T08:19:04.583+0000",
      "_links": {
        "publisher": {
          "href": "http://localhost:8080/api/publishers/1"
        },
        "book": {
          "href": "http://localhost:8080/api/books/2"
        }
      }
    },
    {
      "publishedDate": "2019-07-12T08:19:04.564+0000",
      "_links": {
        "publisher": {
          "href": "http://localhost:8080/api/publishers/1"
        },
        "book": {
          "href": "http://localhost:8080/api/books/1"
        }
      }
    }
  ],
  "_links": {
    "self": {
      "href": "http://localhost:8080/api/publishers/1"
    },
    "publisher": {
      "href": "http://localhost:8080/api/publishers/1"
    },
    "friends": {
      "href": "http://localhost:8080/api/publishers/1/friends"
    },
    "createdBy": {
      "href": "http://localhost:8080/api/publishers/1/contact"
    }
  }
}

我在那里看到属性 bookPublishers 以及链接 friends.恕我直言，它们应该都是关联链接(请参阅 2.4. 创建关联)，其中我可以放置"其他资源吗.

I see there property bookPublishers and also in links friends. Imho they should be both association links (see 2.4. Creating the Associations) where can I "put" another resources.

我想让 spring 渲染 bookPublishers 和朋友一样.

I would like to make spring render bookPublishers same as friends.

示例项目在这里:https://github.com/luvarqpp/poc-springHalRelations

你可以这样做:

git clone https://github.com/luvarqpp/poc-springHalRelations.git
cd poc-springHalRelations
mvn clean spring-boot:run

然后打开http://localhost:8080/api

PS:额外的问题，为业务逻辑提供自己的关系的最简单方法是什么，例如关系renameAuthor".

PS: Bonus question, what is easiest way to provide own relation for business logic, like relation "renameAuthor" for example.

推荐答案

对于集合关系，当相关类型的存储库存在时，Spring Data 将提供一个链接.如果不存在存储库，则集合将内联在响应中，否则，客户端将如何获取数据.

For collection relationships, Spring Data will provide a link when a repository exists for the relevant type. Where no repository exists then the collection will be in-lined in the response, otherwise, how else will the client get the data.

因此，为您的 BookPublisher 类型创建一个存储库.

Therefore, create a repository for your BookPublisher type.

相关文档部分引用:

负责创建指向引用实体(例如对象的 JSON 表示中 _links 属性下的那些对象)的链接的组件.它接受一个@Entity 并遍历其属性，为存储库管理的那些属性创建链接，并在任何嵌入的或简单的属性之间进行复制.

the component responsible for creating the links to referenced entities (such as those objects under the _links property in the object’s JSON representation). It takes an @Entity and iterates over its properties, creating links for those properties that are managed by a Repository and copying across any embedded or simple properties.

您还可以在需要时创建一个内嵌数据的投影.客户端可以在请求中指定此投影，从而防止额外的服务器调用.

You can also create a projection that would in-line the data when required. Clients could specify this projection in the request therefore preventing an additional server call.

例如

/publisher/1?projection=withBookPublishers.

/publisher/1?projection=withBookPublishers.

https://docs.spring.io/spring-data/rest/docs/current/reference/html/#projections-excerpts.projections

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