Spring Data REST-检测到具有相同关系类型的多个关联链接

Question

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

我拿了你的样本项目，http://spring.io/guides/gs/accessing-data-rest/.我能够完成您指南中提到的所有操作（POST、PATCH、PUT、GET）。

然而，我试着在Person-Entity类中添加关系，结果开始崩溃。

@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'
}

电话：

$ curl -i -X POST -H "Content-Type:application/json" -d '{ "firstName":"John", "lastName": "Doe", "personDetails": { "email": "[e-mail]", "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：我能写一篇文章，但我的GET总是失败。

问题2：当Post成功时，为什么会出现此错误？

问题3：有没有一个好的Spring指南可以帮助REST和JPA？如果你还在研究这些模块，我可以看看什么例子？

问题4：@RepositoryRestResource是问题所在吗？除非我将spring数据rest webmvc添加为依赖项，否则无法识别它。

这类似于未回答的问题Spring数据Rest不明确关联异常

更新：

它只在Person类中使用一个OneToOne映射。如果我添加两个类，则在具有OneToOne映射的Person中添加人的详细信息和人的孩子。它不工作。

我还尝试将@JointColumn（name=“person\u details”）和@JointColumn（name=“person\u children”）添加到personDetails和personChildren。它也不起作用。




Answer 1

原因很简单：关联实体的关系名来自包含类的属性名。因此PersonDetails和PersonChildren都希望创建一个指向名为Person的Person的出站链接。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（哪个来自PersonDetails，哪个来自PersonChildren）。

因此，这里有几个选项：

1. 手动命名这些类型的关系。您可以使用@RestResource注释Person属性，并将注释的rel属性配置为与Person不同的属性