我正在尝试开发非常简单的json网络服务,以返回这种形式的数据:
{ "_embedded": { "users": [{ "identifier": "1", "firstName": "John", "lastName": "Doe", "_links": { "self": { "href": "http://localhost:8080/test/users/1" } } }, { "identifier": "2", "firstName": "Paul", "lastName": "Smith", "_links": { "self": { "href": "http://localhost:8080/test/users/2" } } }] }, "_links": { "self": { "href": "http://localhost:8080/test/users" } }, "page": { "size": 20, "totalElements": 2, "totalPages": 1, "number": 0 } }
如您所见,这非常简单。我的POJO扩展了ResourceSupport,因此解析链接没有问题。它们是这样的:
UsersJson(根元素)
public class UsersJson extends ResourceSupport { private List<UserJson> users; [... getters and setters ...] }
用户杰森
public class UserJson extends ResourceSupport { private Long identifier; private String firstName; private String lastName; [... getters and setters ...] }
事实是,我期望jackson和spring足够聪明,可以解析_embedded属性并填充我的UsersJson.users属性,但事实并非如此。
我尝试了在互联网上发现的各种东西,但是我唯一能正常工作的是创建一个充当_embedded包装器的新类:
public class UsersJson extends ResourceSupport { @JsonProperty("_embedded") private UsersEmbeddedListJson embedded; [... getters and setters ...] }
嵌入式“包装器”
public class UsersEmbeddedListJson extends ResourceSupport { private List<UserJson> users; [... getters and setters ...] }
它有效,但我觉得它很丑。
但是我虽然可以使用RestTemplate的以下配置(特别是当我在Jackson2HalModule中看到EmbeddedMapper时),但没有成功:
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); RestTemplate restTemplate = new RestTemplate(Collections.singletonList(converter)); ResponseEntity<UsersJson> result = restTemplate.getForEntity("http://localhost:8089/test/users", UsersJson.class, new HashMap<String, Object>()); System.out.println(result);
有人可以告诉我我在想什么吗?
最后,我找到了一种更好的使用这些application / hal + json API的方法。
实际上,Spring hateoas提供了几乎可以使用的客户端:org.springframework.hateoas.client.Traverson。
Traverson traverson = new Traverson(new URI("http://localhost:8080/test"), MediaTypes.HAL_JSON); TraversalBuilder tb = traverson.follow("users"); ParameterizedTypeReference<Resources<UserJson>> typeRefDevices = new ParameterizedTypeReference<Resources<UserJson>>() {}; Resources<UserJson> resUsers = tb.toObject(typeRefDevices); Collection<UserJson> users= resUsers .getContent();
如您所见,我摆脱了UsersJson和UsersEmbeddedListJson。
这是我添加的Maven依赖项
<dependency> <groupId>org.springframework.hateoas</groupId> <artifactId>spring-hateoas</artifactId> <version>0.19.0.RELEASE</version> </dependency> <dependency> <groupId>org.springframework.plugin</groupId> <artifactId>spring-plugin-core</artifactId> <version>1.2.0.RELEASE</version> </dependency> <dependency> <groupId>com.jayway.jsonpath</groupId> <artifactId>json-path</artifactId> <version>2.0.0</version> </dependency>