使用基于HAL的REST服务和spring-hateoas

Question

我正在尝试通过RestTemplate类使用基于HAL的REST服务。响应正文如下所示：

{
  "_embedded": {
    "school:teachers": [
      {
        "name": "Adams",
        "state": "CA",
        "_links": {
          "self": {
            "href": "http://localhost:8080/api/teachers/1"
          }
        }
      },
      {
        "name": "Barnes",
        "state": "FL",
        "_links": {
          "self": {
            "href": "http://localhost:8080/api/teachers/2"
          }
        }
      },
      {
        "name": "Armstrong",
        "state": "GA",
        "_links": {
          "self": {
            "href": "http://localhost:8080/api/teachers/3"
          }
        }
      }
    ]
  },
  "_links": {
    "curies": [
      {
        "href": "http://localhost:8080/docs/html5/{rel}.html",
        "name": "school",
        "templated": true
      }
    ]
  }
}

Teacher类如下所示：

public class Teacher {
    private String name;
    private String state;

    // getters and setters...
}

GET方法的REST服务的返回类型为ResponseEntity<Resources<Resource<Component>>>。因此，我在客户端代码中的请求如下所示：

...
RestTemplate restTemplate = new RestTemplate();

Map<String, Object> dummy = new HashMap<>();
HttpEntity<String> httpEntity = getHttpEntity(); 

ResponseEntity<Resources<Resource<Teacher>>> response = restTemplate.exchange(url,
                HttpMethod.GET,
                httpEntity,
                new ParameterizedTypeReference<Resources<Resource<Teacher>>>() {});

Resources<Resource<Teacher>> resources = response.getBody();
...

当我使用响应类型ParameterizedTypeReference发出请求时，响应的内容是空的。当我使用String执行此操作时，我会检索内容列表。

我应该如何使用响应类型ParameterizedTypeReference来请求检索它，以便将它直接映射到POJO中？

Answer 1

当然，你应该选择Traverson

Traverson client = new Traverson(new URI("http://localhost:8080/api/"), 
         MediaTypes.HAL_JSON);
    Resources<Resource<Teacher>> teachers = client
        .follow("school:teachers")
        .toObject(new ResourcesType<Resource<Teacher>>(){});

https://docs.spring.io/spring-hateoas/docs/current/reference/html/#client.traverson

Answer 2

我尝试了一种类似于Vishnoo Rath的方法。我计划为我所有的资源建立一个通用的方法来做这件事。

ResponseEntity<String> response = 
                restTemplate.exchange("http://localhost:8081/rest/cars", HttpMethod.GET, null, String.class);

        String data = response.getBody();
        //log.info(data);

        ObjectMapper om = new ObjectMapper();
        om.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

        JsonNode jsNode = om.readTree(data);
        String test = jsNode.at("/_embedded/cars").toString();
        //log.info(test);

        ArrayList<Car> cars = om.readValue(test, new TypeReference<List<Car>>() {
        });

        for (Car theCar : cars) {
            log.info(">>> " + theCar.getMake() + " " + theCar.getModel() + " " + theCar.getYear());
        }

Answer 3

在Java语言中，我使用Bowman来消耗JSON+HAL资源。与this article中所示的RestTemplate相比，该库极大地简化了资源消耗。