Spring Data Rest - _links [英] Spring Data Rest - _links

问题描述

编辑 14/08/14 13:29

我的下一个结论是，我的@RepositoryRestResource CrudRepository 生成的 hal+json 格式不正确.

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

<代码>{_链接":{人们" : {"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:

<代码>{链接":[{"rel" : "客户","href" : "http://localhost:8080/customer"}, {"rel" : "个人资料","href" : "http://localhost:8080/profile"}}

有人知道这是为什么吗?

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

编辑 14/08/14:我的调试更进了一步.通过提供我自己的 org.springframework.hateoas.ResourceSupport 类实现，它检查 json 中的_links"而不是links"，我更进一步.错误是:

<块引用>

无法从 START_OBJECT 令牌中反序列化 java.util.ArrayList 的实例..... 通过引用链:com.ebs.solas.admin.test.SolicitorDTO[\"_links\"]"

这是因为 org.springframework.hateoas.ResourceSupport 类似乎要求 links 属性是一个 json 数组.并且默认情况下，Spring Data 为 Rest Entity 生成的 json+hal 输出不会生成数组(没有方括号):

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

希望来自 Spring 论坛的人可以在这里帮助我.

================================================/p>

请查看我的 Spring Data 存储库代码大纲:

@RepositoryRestResource公共接口 SolicitorFirmRepository 扩展了 CrudRepository{}@实体@休息资源@Table(name="XXXX", schema = "XXX")公共类 SolicitorFirm 实现了 Serializable {}

这成功生成了以下 hatoas 资源:

<代码>{"firmNumber" : "FXXXX",律师类型":r"，"公司名称": "XXXX","address1" : "XXXX",地址2":XXX"，地址3":XXX"，地址4":空，"电话号码": "XXXXX","传真号码": "XXXXX","县" : "OY",_链接":{自己" : {"href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/XXXX"},律师":{"href" : "http://localhost:9090/solas-admin-data-api/solicitorFirms/XXXX/solicitors"}}

但是，当我为客户端/控制器使用定义 DTO 时:

import org.springframework.hateoas.ResourceSupport;公共类 SolicitorFirmDTO 扩展 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");

我收到以下错误:

<块引用>

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException:无法识别的字段_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 Data Rest 生成的 json 在 _links 下添加了实体链接，而 HATEOAS 资源超类需要 links?

有人可以帮忙吗?这是版本问题还是我需要一些额外的配置来将 _links 映射到 links

我尝试了 MappingJackson2HttpMessageConverter 和各种媒体类型 application/json+hal 都无济于事.

解决方案

也与 mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) 一起使用 @JsonIgnoreProperties(ignoreUnknown = true) 在每个实体上:

@Entity@JsonIgnoreProperties(ignoreUnknown = true)公共类用户{...}

Edit 14/08/14 13:29

My next conclusion is that the hal+json format produced from my @RepositoryRestResource CrudRepository is incorrect.

The tutorial (http://spring.io/guides/gs/accessing-data-rest/) shows the output of a hypermedia Rest JPA entity as: (please note there is no "rel" element, and "links" is not an array)

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

However, the reference docs (http://docs.spring.io/spring-data/rest/docs/1.1.x/reference/html/intro-chapter.html) show that the output should be:

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

Does anyone know why this is?

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

Edit 14/08/14: I have taken my debugging a step further. By providing my own implementation of a org.springframework.hateoas.ResourceSupport class, which inspects the json for "_links" rather than "links" I get a step further. The error is:

"Can not deserialize instance of java.util.ArrayList out of START_OBJECT token ..... through reference chain: com.ebs.solas.admin.test.SolicitorDTO[\"_links\"]"

This is because the org.springframework.hateoas.ResourceSupport class seems to require that the links attribute be a json array. And by default the json+hal output produced by Spring Data for a Rest Entity does not produce an array (there are no square brackets):

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

Hopefully someone from the Spring forums could help me here.

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

please see an outline of my Spring Data repository code:

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

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

This successfully generates the following hateoas resource:

{
"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"
    }
 }

HOWEVER, when i define a DTO for clientside/controller use:

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

and use the following code

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

I get the following error:

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "_links" (class com.ebs.solas.admin.test.SolicitorFirmDTO), not marked as ignorable (7 known properties: xx])

For some reason the json produced by Spring Data Rest adds the entity links under _links while the HATEOAS resource superclass expects links?

Can any one help? is this a version issue or do I need some extra configuration to map _links to links

I have tried MappingJackson2HttpMessageConverter and various media types application/json+hal to no avail.

解决方案

Also with mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) use @JsonIgnoreProperties(ignoreUnknown = true) on every Entity:

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

}

这篇关于Spring Data Rest - _links的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！