春季数据Rest - _links

Question

编辑14/08/14 13:29

我的下一个结论是，我的@RepositoryRestResource CrudRepository生成的hal+json格式是不正确的。

本教程(http://spring.io/guides/gs/accessing-data-rest/)将超媒体Rest实体的输出显示为：(请注意没有"rel“元素，并且”link“不是数组)

{
   "_links" : {
       "people" : {
           "href" : "http://localhost:8080/people{?page,size,sort}"
       }
   }
 }

但是，参考文档(http://docs.spring.io/spring-data/rest/docs/1.1.x/reference/html/intro-chapter.html)显示输出应该是：

{
    "links" : [ {
        "rel" : "customer",
        "href" : "http://localhost:8080/customer"
      }, {
         "rel" : "profile",
         "href" : "http://localhost:8080/profile"
      }
 }

有人知道这是为什么吗？

=====================================

编辑14/08/14:我已经进一步调试了。通过提供我自己的org.springframework.hateoas.ResourceSupport类的实现(它检查json中的"_links“而不是”链接“)，我得到了进一步的进展。错误是：

“不能将java.util.ArrayList的实例反序列化出START_OBJECT令牌.通过引用链:START_OBJECT

这是因为org.springframework.hateoas.ResourceSupport类似乎要求链接属性是一个json数组。默认情况下，Spring为Rest实体生成的json+hal输出不产生数组(没有方括号)：

"_links" : {
  "self" : {
    "href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/Fxxx"
  },
  "solicitors" : {
    "href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/Fxxx/solicitor
  }
}

希望春天论坛的人能在这里帮助我。

==============================================

请参阅我的Spring数据存储库代码的大纲：

@RepositoryRestResource
    public interface SolicitorFirmRepository extends CrudRepository<SolicitorFirm, String> {
}

@Entity
@RestResource
@Table(name="XXXX", schema = "XXX")
public class SolicitorFirm implements Serializable {
}

这将成功地生成以下hateoas资源：

{
"firmNumber" : "FXXXX",
"solicitorType" : "r",
"companyName" : "XXXX",
"address1" : "XXXX",
"address2" : "XXX",
"address3" : "XXX",
"address4" : null,
"phoneNumber" : "XXXXX",
"faxNumber" : "XXXXX",
"county" : "OY",
"_links" : {
    "self" : {
        "href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/XXXX"
    },
    "solicitors" : {
        "href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/XXXX/solicitors"
    }
 }

但是，当我为客户端/控制器定义DTO时，请使用：

import org.springframework.hateoas.ResourceSupport;
public class SolicitorFirmDTO extends ResourceSupport {
   .....
}

并使用以下代码

RestTemplate rt = new RestTemplate();
String uri = new String("//xxxxx:9090/solas-admin-data-api/solicitors/Sxxxxx");
SolicitorFirmDTO u = rt.getForObject(uri, SolicitorFirmDTO.class, "SXXXX");

我得到以下错误：

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException:未识别字段"_links“(com.ebs.solas.admin.test.SolicitorFirmDTO类)，未标记为可忽略(7个已知属性:xx)

出于某种原因，Spring生成的json在_links下添加实体链接，而HATEOAS资源超类则期望links

有人能帮忙吗？这是版本问题还是需要额外的配置才能将_links映射到links？

我尝试过MappingJackson2HttpMessageConverter和各种媒体类型的application/json+hal，但都没有效果。

Answer 1

对于mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)，也可以在每个实体上使用@JsonIgnoreProperties(ignoreUnknown = true)：

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
public class User {
    ...

}

Answer 2

对于Spring 1.3.3，用于列表的方法exchange()正在工作

public void test1() {

    RestTemplate restTemplate = restTemplate();

    ParameterizedTypeReference<PagedResources<User>> responseTypeRef = new ParameterizedTypeReference<PagedResources<User>>() {
    };

    String API_URL = "http://localhost:8080/api/v1/user"
    ResponseEntity<PagedResources<User>> responseEntity = restTemplate.exchange(API_URL, HttpMethod.GET,
            (HttpEntity<User>) null, responseTypeRef);

    PagedResources<User> resources = responseEntity.getBody();
    Collection<User> users = resources.getContent();
    List<User> userList = new ArrayList<User>(users);

    System.out.println(userList);

}

private 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);

    List<HttpMessageConverter<?>> converterList = new ArrayList<HttpMessageConverter<?>>();
    converterList.add(converter);
    RestTemplate restTemplate = new RestTemplate(converterList);

    return restTemplate;
}

Answer 3

谢谢你的回应。

为了回答你的问题，

1)我相信我的输入和输出都是HAL。您将从我最初的文章中看到，从my @RepositoryRestResource生成的json是HAL (注意它包含指向自身和相关实体的ref链接)：

{
  "firmNumber" : "Fxx",
  "solicitorType" : "r",
  "companyName" : "xxx",
  "address1" : "xxx,",
  "address2" : "xx,",
  "address3" : "xxx,",
  "_links" : {
      "self" : {
         "href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/Fxx"
      },
      "solicitors" : {
         "href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/Fxx/solicitors
     }
  }
}

然而，引用链接在属性名"_links“下，但是客户端的RestSupport类似乎不需要任何_underscore，它似乎只搜索”链接“。

2)是的，我指定了@EnableHypermediaSupport(type = HypermediaType.HAL)，

请参阅下面的完整配置如下(javaconfig)：

@Configuration
@ComponentScan("com.ebs.solas.admin")
@EnableJpaRepositories("com.ebs.solas.admin")
@EnableTransactionManagement
@Import(RepositoryRestMvcConfiguration.class)
class ApplicationConfig {

    @Bean
    public DataSource dataSource() {

          DriverManagerDataSource dataSource = new DriverManagerDataSource();
          dataSource.setDriverClassName("com.ibm.db2.jcc.DB2Driver");
          dataSource.setUrl("jdbc:db2://xxxx:52001/xxxx");
          dataSource.setUsername( "xxx" );
          dataSource.setPassword( "xxx" );
          return dataSource;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setDatabase(Database.DB2);
        vendorAdapter.setGenerateDdl(false);
        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan("com.ebs.solas.admin");
        factory.setDataSource(dataSource());
        return factory;
    }

    @Bean
    public PlatformTransactionManager transactionManager() {
        JpaTransactionManager txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory().getObject());
        return txManager;
    }
}


public class RestWebApplicationInitializer implements WebApplicationInitializer { 

    public void onStartup(ServletContext context) throws ServletException {
        AnnotationConfigWebApplicationContext rootContext = new AnnotationConfigWebApplicationContext();
        rootContext.register(ApplicationConfig.class);

        context.addListener(new ContextLoaderListener(rootContext));

        RepositoryRestDispatcherServlet exporter = new RepositoryRestDispatcherServlet();
        ServletRegistration.Dynamic reg = context.addServlet("exporter", exporter);
        reg.setLoadOnStartup(1);
        reg.addMapping("/*");
    }
}


@Configuration
@ComponentScan("com.ebs.solas.admin")
@EnableWebMvc
@EnableHypermediaSupport(type = HypermediaType.HAL)
class WebMVCConfiguration extends WebMvcConfigurationSupport {

    @Override
    public void configureContentNegotiation(ContentNegotiationConfigurer c) {
        c.defaultContentType(MediaType.APPLICATION_JSON);
    }

    @Bean
    public MultipartResolver multipartResolver() { 
        return new StandardServletMultipartResolver();
    }
}

我的RestController还指定RestTemplate应该使用hal+json消息转换格式，参见下面

@RestController
public class TestController {

     @RequestMapping(value="/test", method=RequestMethod.GET, produces={"application/hal+json"})
     @ResponseStatus(HttpStatus.OK)
     public SolicitorDTO doTest() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(new Jackson2HalModule());

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

        RestTemplate rt = new RestTemplate();
        rt.getMessageConverters().add(converter);


        String uri = new String("http://localhost:9090/solas-admin-data-api/solicitors/{id}");
        SolicitorDTO u = rt.getForObject(uri, SolicitorDTO.class, "Sxxxxx");
        return u;
     }   
}

谢谢你的帮助，appdJava