PagedResources<Resource 和 RestTemplate 不起作用答案

【问题标题】：PagedResources<Resource and RestTemplate does not worksPagedResources<Resource 和 RestTemplate 不起作用
【发布时间】：2020-03-25 01:22:47
【问题描述】：

我正在使用 Spring Boot REST 示例。在此，我使用 RestTemplate 调用返回 PagedResources<Resource<EmployeeDto>> Object 的端点。但是当通过RestTemplate调用时，我没有得到任何内容。但是，此服务构建在另一个微服务中，可以通过 Web 轻松访问，并且可以通过 Postman 调用。

@GetMapping("/{employeeId}/employees")
public PagedResources<Resource<EmployeeDto>> getEmployyes(@PathVariable(name="employeeId") String employeeId, 
        @RequestParam(defaultValue="0",required = false, name="page") Integer page, 
        @RequestParam(defaultValue="25",required = false, name = "size") Integer size,
        @RequestParam(defaultValue="billingNumber") String sortParam,
        @RequestParam(defaultValue="ASC",required = false) Direction direction,
        Pageable pageable, HttpServletRequest request) throws IOException{

    return employeeService.getEmployeesByCid(employeeId, request);
}

我使用下面的代码，它没有给我任何内容。

String uri = "http://localhost:8080/employee-api/employees/160166/employees?page=0&size=25";

RestTemplate template = new RestTemplate();
ResponseEntity<PagedResources<Resource<EmployeeDto>>> studentResponse = template
        .exchange(uri, HttpMethod.GET, null, new TypeReferences.PagedResourcesType<Resource<EmployeeDto>>(){});
System.out.println(studentResponse.getBody());

如果我在下面使用，那么我会得到响应。

final ResponseEntity<String> studentResponse = template
                .exchange(URL, HttpMethod.GET, null, String.class);

注意：如果我通过 Postman 执行代码，我会得到以下响应。

{
  "_embedded": {
    "employeeDto": [
      {
        "employeeNumber": "3109194",
        "status": "A"
      },
      {
        "employeeNumber": "3109224",
        "status": "A"
      },
      {
        "employeeNumber": "3109514",
        "status": "A"
      },
      {
        "employeeNumber": "3109519",
        "status": "A"
      }
    ]
  },
  "_links": {
    "first": {
      "href": "http://localhost:8080/customers/1/employee-numbers?sortParam=employeeNumber&page=0&size=4&sort=employeeNumber,asc"
    },
    "prev": {
      "href": "http://localhost:8080/customers/1/employee-numbers?sortParam=employeeNumber&page=0&size=4&sort=employeeNumber,asc"
    },
    "self": {
      "href": "http://localhost:8080/customers/1/employee-numbers?sortParam=employeeNumber&page=1&size=4&sort=employeeNumber,asc"
    },
    "next": {
      "href": "http://localhost:8080/customers/1/employee-numbers?sortParam=employeeNumber&page=2&size=4&sort=employeeNumber,asc"
    },
    "last": {
      "href": "http://localhost:8080/customers/1/employee-numbers?sortParam=employeeNumber&page=3&size=4&sort=employeeNumber,asc"
    }
  },
  "page": {
    "size": 4,
    "totalElements": 14,
    "totalPages": 4,
    "number": 1
  }
}

【问题讨论】：

标签： java spring-boot resttemplate pageable

【解决方案1】：

我通过查看http://izeye.blogspot.com/2015/01/consume-spring-data-rest-hateoas-hal.html 和Why does RestTemplate not bind response representation to PagedResources? 解决了这个问题。

但是，这是我开发的代码，效果很好。

public class Demo {
    private static RestTemplate restTemplate() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        mapper.registerModule(new Jackson2HalModule());

        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        converter.setSupportedMediaTypes(MediaType.parseMediaTypes("application/hal+json"));
        converter.setObjectMapper(mapper);

        return new RestTemplate(Collections.<HttpMessageConverter<?>> singletonList(converter));
    }

    public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {
        String URL = "http://localhost:8080/employee-api/employees/160166/employees?page=0&size=25";

        RestTemplate restTemplate = restTemplate();

        ResponseEntity<PagedResources<Resource<EmployeeDto>>> result = restTemplate.exchange(URL, HttpMethod.GET,
                null/* httpEntity */, new ParameterizedTypeReference<PagedResources<Resource<EmployeeDto>>>() {});
        PagedResources<Resource<EmployeeDto>> body = result.getBody();
        ObjectMapper mapper = new ObjectMapper();
        String writeValueAsString = mapper.writeValueAsString(body);

        System.out.println(mapper.writeValueAsString(body));
    }
}

【讨论】：