Question

我有一个Web应用程序，其中我使用带有HypermediaType HAL的Spring Hateoas的Spring MVC。在我的Controller中，我使用Resources Class放入Subjects列表。问题是，如果我放入一个元素的列表，结果json的结构区别于我是否放入2个元素。如果列表只包含一个元素，则删除列表并将其作为单个对象返回。在两个Controller方法下面，我粘贴了生成的Json。

我现在想知道，为什么行为是这样的，我怎么能强迫Hateoas在结果json中使用列表？

@Controller
@RequestMapping(value = "/collections")
public class CollectionController {

    @RequestMapping
    public HttpEntity<Resources<Subject>> getOneSubject() {

        Subject subject = new Subject();
        Resources<Subject> subjects = new Resources<>(asList(subject));

        return new ResponseEntity<>(subjects, HttpStatus.OK);
    }
/*HTTP-Response Body:
{
    "_embedded": {
        "subject": {
            "name": null
        }
    }
}
*/


    @RequestMapping
    public HttpEntity<Resources<Subject>> getTwoSubjects() {

        Subject subject = new Subject();
        Resources<Subject> subjects = new Resources<>(asList(subject, subject));

        return new ResponseEntity<>(subjects, HttpStatus.OK);
    }
/*HTTP-Response Body:
{
    "_embedded": {
        "subjectList": [
            {
                "name": null
            },
            {
                "name": null
            }
        ]
    }
}*/

}

Hateoas配置：

@Configuration
@EnableHypermediaSupport(type = EnableHypermediaSupport.HypermediaType.HAL)
public class HateoasConfig {
}

Answer 1

我可以在以下步骤之后获得您提供的示例项目：

升级至兼容的Jackson版本（2.3.0或更高版本）。使用Spring HATEOAS 0.10.0.BUILD-SNAPSHOT。
运行应用程序。
curl -v -H "Accept: application/hal+json" http://localhost:8080/api/subjects

结果：

* Adding handle: conn: 0x7fc072803a00
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x7fc072803a00) send_pipe: 1, recv_pipe: 0
* About to connect() to localhost port 8080 (#0)
*   Trying ::1...
* Connected to localhost (::1) port 8080 (#0)
> GET /api/subjects HTTP/1.1
> User-Agent: curl/7.30.0
> Host: localhost:8080
> Accept: application/hal+json
> 
< HTTP/1.1 200 OK
< Content-Type: application/hal+json
< Transfer-Encoding: chunked
* Server Jetty(8.1.14.v20131031) is not blacklisted
< Server: Jetty(8.1.14.v20131031)
< 
* Connection #0 to host localhost left intact
{"_links":{"self":{"href":"http://localhost:8080/api/subjects"}},"_embedded":{"subjectList":[{"name":"foo"}]}}

结果JSON具有不同的结构

1 个答案: