无法在Spring Data REST请求中保存OneToMany / ManyToOne关系

问题描述

我正在使用Spring Data JPA和Spring Data Rest。 发出REST请求以保留实体时，出现下一个错误：

org.springframework.dao.DataIntegrityViolationException: not-null property references a null or transient value

我的数据模型具有以下实体：

合同：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING)
public class Contract implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @OneToMany(
            cascade = CascadeType.ALL,orphanRemoval = true,fetch = FetchType.LAZY,mappedBy="contract"
    )
    private List<Participation> participants = new ArrayList<Participation>();

    private String name;

}   

参与：

@Entity
public class Participation implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
        
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(nullable = false) //By default the column will be CONTRACT_ID
    private Contract contract;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(nullable = false)
    private Contact contact;

    private String clauses;
}

联系方式：

@Entity
public class Contact implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private String emailAddress;
}

我有2个JPAR存储库：

public interface ContractRepository extends JpaRepository<Contract,Long> {
    List<Contract> findByNameContainsIgnoreCase(String name);
}

public interface ContactRepository extends JpaRepository<Contact,Long> {
}

要保存有几个参与者的新合同，我在邮递员中进行下一步：

1. 创建合同并获取其href：

请求：POST http：// localhost：8080 / api / contracts

身体：

{
   "name": "Contract1"
}

响应成功：

201 Created
{
  "name": "Contract1","participants": [],"_links": {
    "self": {
      "href": "http://localhost:8080/api/contracts/4"
    },"contract": {
      "href": "http://localhost:8080/api/contracts/4"
    },}
}

1. 到目前为止一切顺利。既然合同已经生效，我将添加参与者： 联系人1已存在于数据库中。

请求：PATCH http：// localhost：8080 / api / contracts / 4

身体：

{
    "participants": [
        {
            "clauses": "Bla bla bla","contact": {
            "href": "http://localhost:8080/api/contacts/1"
            },"contract": {
            "href": "http://localhost:8080/api/contracts/4"
            }
        }
    ]
}

执行此请求时，系统会抱怨现场/ fk合同：

{
    "cause": {
        "cause": null,"message": "not-null property references a null or transient value : com.xxx.xxx.model.Participation.contract"
    },"message": "not-null property references a null or transient value : com.xxx.xxx.model.Participation.contract; nested exception is org.hibernate.PropertyValueException: not-null property references a null or transient value : com.xxx.xxx.model.Participation.contract"
}

我尝试了几种参与方式来引用合同，例如：

"contract": "http://localhost:8080/api/contracts/4"

没有运气。由于某种原因，系统会将字段留空，而不是使用在步骤1中创建的实体的前键。 我在做什么错了？

解决方法

问题可以通过以下方式解决：

1. 添加新的存储库ParticipationRepository（扩展JpaRepository）；
2. 首先创建没有参与的合同：

POST http：// localhost：8080 / api / contracts {“ name”：“ Contract1”}

响应：

201 Created
{
  "name": "Contract1","_links": {
    "self": {
      "href": "http://localhost:8080/api/contracts/3"
    },"contract": {
      "href": "http://localhost:8080/api/contracts/3"
    },"participants": {
      "href": "http://localhost:8080/api/contracts/3/participants"
    }
  }
}

1. 创建一个参与并使用刚创建的合同中的URI来设置FK。假设联系人1已存在于数据库中。

POST http：// localhost：8080 / api / participations { “ clauses”：“ bla，bla，bla”， “ contract”：“ http：// localhost：8080 / api / contracts / 3”， “ contact”：“ http：// localhost：8080 / api / contacts / 1”}

响应：

201 Created
{
  "clauses": "bla,bla,bla","_links": {
    "self": {
      "href": "http://localhost:8080/api/participations/5"
    },"participation": {
      "href": "http://localhost:8080/api/participations/5"
    },"contract": {
      "href": "http://localhost:8080/api/participations/5/contract"
    },"contact": {
      "href": "http://localhost:8080/api/contacts/5/contact"
    }
  }
}