Spring Data REST - 检测到具有相同关系类型的多个关联链接

我正在尝试做一个简单的 Spring 应用程序。它需要公开 REST 端点并将其保存到关系数据库。

我拿了你的示例项目，http://spring.io/guides/gs/accessing-data-rest/。我能够执行您指南中提到的所有操作（POST、PATCH、PUT、GET）。

然而，我尝试创建添加关系到 Person Entity 类，但事情开始崩溃。

@Entity
public class Person {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    private String firstName;
    private String lastName;

    @OneToOne(cascade = {CascadeType.ALL})
    private PersonDetails personDetails;

    @OneToOne(cascade = {CascadeType.ALL})
    private PersonChildren personChildren;

     ///Getter and setters for everything except id.
}


@Entity
public class PersonChildren {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    private String childFirstName;
    private String childLastName;

    @OneToOne(mappedBy="personChildren", optional=false)
    private Person person;

///Getter and setters for everything except id.
}


@Entity
public class PersonDetails {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    private String email;
    private String phoneNumber;

    @OneToOne(mappedBy="personDetails",optional=false)
    private Person person;

///Getter and setters for everything except id.
}


@RepositoryRestResource(collectionResourceRel = "people", path = "people")
public interface PersonRepository extends PagingAndSortingRepository<Person, Long> {

    List<Person> findByLastName(@Param("name") String name);

}

build.gradle

buildscript {
    repositories {
        maven { url "http://repo.spring.io/libs-release" }
        mavenLocal()
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:1.1.1.RELEASE")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'idea'
apply plugin: 'spring-boot'

jar {
    baseName = 'gs-accessing-data-rest'
    version = '0.1.0'
}

repositories {
    mavenLocal()
    mavenCentral()
    maven { url "http://repo.spring.io/libs-release" }
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    compile("org.springframework.boot:spring-boot-starter-data-jpa")
    compile("com.h2database:h2")
    compile("org.springframework.data:spring-data-rest-webmvc")
}

task wrapper(type: Wrapper) {
    gradleVersion = '1.11'
}

Call:

$ curl -i -X POST -H "Content-Type:application/json" -d '{ "firstName":"John", "lastName": "Doe", "personDetails": { "email": "[email protected]", "phoneNumber": "001-002-0003" }, "personChildren": {"childFirstName": "Mary", "childLastName": "Martin" } }' <code> http://localhost:8080/people </code>

Response: 
HTTP/1.1 201 Created
Server: Apache-Coyote/1.1
<code>
Location: http://localhost:8080/people/1
</code>
Content-Length: 0
Date: Thu, 26 Jun 2014 05:42:45 GMT

$ curl  http://localhost:8080/people

{
  "timestamp" : 1403761371011,
  "status" : 500,
  "error" : "Internal Server Error",
  "exception" : "org.springframework.http.converter.HttpMessageNotWritableException",
  "message" : "Could not write JSON: Detected multiple association links with same relation type! Disambiguate association @javax.persistence.OneToOne(optional=false, targetEntity=void, cascade=[], fetch=EAGER, orphanRemoval=false, mappedBy=personChildren) private com.ds.dao.rest.Person com.ds.dao.rest.PersonChildren.person using @RestResource! (through reference chain: org.springframework.hateoas.PagedResources[\"_embedded\"]->java.util.UnmodifiableMap[\"people\"]->java.util.ArrayList[0]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Detected multiple association links with same relation type! Disambiguate association @javax.persistence.OneToOne(optional=false, targetEntity=void, cascade=[], fetch=EAGER, orphanRemoval=false, mappedBy=personChildren) private com.ds.dao.rest.Person com.ds.dao.rest.PersonChildren.person using @RestResource! (through reference chain: org.springframework.hateoas.PagedResources[\"_embedded\"]->java.util.UnmodifiableMap[\"people\"]->java.util.ArrayList[0])",
  "path" : "/people"
}

问题 1：我可以发帖，但 GET 一直失败。

问题2：为什么Post成功后会出现这个错误？

问题 3：是否有一个好的 Spring 指南可以帮助您使用 REST 和 JPA？如果您仍在研究这些模块，我可以看哪些示例？

问题 4：@RepositoryRestResource 是问题所在吗？除非我添加 spring-data-rest-webmvc 作为依赖项，否则它不会被识别。

这与未回答的问题类似Spring Data Rest 不明确关联异常

Update:

它只与一个一起工作OneToOne映射到Person班级。如果我添加两个类，personDetails and personChildren in Person with OneToOne映射。它不起作用。

我也尝试添加@JointColumn(name="person_details") and @JointColumn(name="person_children") to personDetails and personChildren。它也不起作用。

原因非常简单：关联实体的关系名称源自包含类的属性名称。所以两者PersonDetails and PersonChildren想要创建一个出站链接Person named person。如果我们渲染它，它看起来会像这样

{ _links : { 
   person : { href : … }, <- the one from PersonDetails
   person : { href : … }  <- the one from PersonChildren
}

这当然是无效的。此外，将两个链接排列在一个数组中将不再允许您区分这两个链接（哪个链接来自PersonDetails以及哪一个来自PersonChildren.

所以这里有几个选择：

1. 手动命名这些类型的关系。您可以注释Person属性与@RestResource并配置rel注释的属性不同于person.
2. 您希望两者中的任何一个根本不导出。可以使用完全相同的注释来防止链接被渲染。只需设置exported标记在@RestResource to false并且链接不会被渲染。如果指针例如从PersonDetails仅与代码相关，但实际上与 JSON 表示形式无关。