Java 使用json+；使用spring RestTemplate的hal_嵌入式资源

我有一个简单的用例，我想使用一个用json+hal表示的资源集合

我使用spring Rest模板，并将其配置为使用Jackson2HalModule。 调试代码时，我发现响应对象确实包含准确的元数据（例如页面和资源的数量）和响应头，但没有内容或链接。在过去的一天里，我在互联网上阅读了许多文章和指南，我觉得我的定制rest模板应该能够根据我的发现为我的用例工作

如果有人能解释这一点，我将万分感激

我的服务代码如下：

@Service
public class EventServiceImpl extends BaseService implements EventService {

private static final String knownEntity = "59d786d642572853721728f6";

private static  String SERVICE_URL = "http://EVENTS-SERVER";

private static String EVENTS_PATH = "/events";


@Autowired
@LoadBalanced
protected RestTemplate restTemplate;

@Override
public ResponseEntity<PagedResources<Event>> fetchEventsList() {
    // acceptable media type
    List<MediaType> acceptableMediaTypes = Arrays.asList(HAL_JSON);

    // header
    HttpHeaders headers = new HttpHeaders();
    headers.setAccept(acceptableMediaTypes);

    HttpEntity<String> entity = new HttpEntity<String>(null, headers);

    ResponseEntity<PagedResources<Event>> response = getRestTemplateWithHalMessageConverter()
            .exchange(SERVICE_URL + EVENTS_PATH, HttpMethod.GET, entity, new ParameterizedTypeReference<PagedResources<Event>>(){});
    return response;
}

public RestTemplate getRestTemplateWithHalMessageConverter() {
    List<HttpMessageConverter<?>> existingConverters = restTemplate.getMessageConverters();
    List<HttpMessageConverter<?>> newConverters = new ArrayList<>();
    newConverters.add(getHalMessageConverter());
    newConverters.addAll(existingConverters);
    restTemplate.setMessageConverters(newConverters);
    return restTemplate;
}

private HttpMessageConverter getHalMessageConverter() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.registerModule(new Jackson2HalModule());
    MappingJackson2HttpMessageConverter halConverter = new TypeConstrainedMappingJackson2HttpMessageConverter(ResourceSupport.class);
    objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    halConverter.setSupportedMediaTypes(Arrays.asList(HAL_JSON));
    halConverter.setObjectMapper(objectMapper);
    return halConverter;
}

}

为了完整起见，下面是我尝试使用的hal+json的一个示例：

{
"_embedded": {
    "events": [
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "CANCELLED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6"
                },
                "reinstate": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6/reinstate"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6/reschedule"
                }
            }
        },
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "ADVERTISED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6"
                },
                "cancel": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6/cancel"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6/reschedule"
                }
            }
        },
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "ADVERTISED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7"
                },
                "cancel": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7/cancel"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7/reschedule"
                }
            }
        },
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "ADVERTISED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8"
                },
                "cancel": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8/cancel"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8/reschedule"
                }
            }
        }
    ]
},
"_links": {
    "self": {
        "href": "http://192.168.1.6:2221/events{?page,size,sort}",
        "templated": true
    },
    "profile": {
        "href": "http://192.168.1.6:2221/profile/events"
    }
},
"page": {
    "size": 20,
    "totalElements": 4,
    "totalPages": 1,
    "number": 0
}

}

---

编辑：我可以毫无问题地使用单个事件。

我有一个类似的问题，我最终使用了

org.springframework.hateoas.Resources

对于下面的示例，该对象位于

org.springframework.hateoas:spring-hateoas:jar:0.25.2.RELEASE

它是从

org.springframework.boot:spring-boot-starter-data-rest:jar:2.1.7.RELEASE

中引入的，因此假设您声明

spring-boot-starter-data-rest

依赖项，它很可能已经在您的类路径中了

下面是一个简单的示例（使用您的信息）：

RestTemplate RestTemplate=new RestTemplate（）；
Resources resourceEvents=restTemplate.getForObject（“http://192.168.1.6:2221/events“，资源类）；
列表事件=新的ArrayList（resourceEvents.getContent（））；

可能会有一些问题让事情变得不那么直截了当，但希望这能为解决你的问题提供一个开始

{
"_embedded": {
    "events": [
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "CANCELLED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6"
                },
                "reinstate": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6/reinstate"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d786d642572853721728f6/reschedule"
                }
            }
        },
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "ADVERTISED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6"
                },
                "cancel": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6/cancel"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d7f14342572812ceca7fc6/reschedule"
                }
            }
        },
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "ADVERTISED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7"
                },
                "cancel": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7/cancel"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d7f14742572812ceca7fc7/reschedule"
                }
            }
        },
        {
            "name": null,
            "location": null,
            "capacity": 0,
            "currentState": "ADVERTISED",
            "_links": {
                "self": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8"
                },
                "event": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8"
                },
                "cancel": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8/cancel"
                },
                "reschedule": {
                    "href": "http://192.168.1.6:2221/events/59d7f14c42572812ceca7fc8/reschedule"
                }
            }
        }
    ]
},
"_links": {
    "self": {
        "href": "http://192.168.1.6:2221/events{?page,size,sort}",
        "templated": true
    },
    "profile": {
        "href": "http://192.168.1.6:2221/profile/events"
    }
},
"page": {
    "size": 20,
    "totalElements": 4,
    "totalPages": 1,
    "number": 0
}

RestTemplate restTemplate = new RestTemplate();
Resources<Event> resourceEvents = restTemplate.getForObject("http://192.168.1.6:2221/events", Resources.class);
List<Event> events = new ArrayList<>(resourceEvents.getContent());