无法在Spring数据REST请求中保存OneTomany/ManyToOne关系

Question

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

@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;

}   

@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;
}

@Entity
public class Contact implements Serializable {

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

    private String name;
    private String emailAddress;
}

我有2个JParepository：

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

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

为了保存一份有几个参与者的新合同，我正在邮递员中执行以下步骤：

1. 创建契约并获取其href:

{
   "name": "Contract1"
}

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

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

{
    "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"
}

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

没运气。出于某种原因，系统将该字段留空，而不是使用步骤1中创建的实体的foreing键。我做错了什么？

Answer 1

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. 首先创建一个没有参与的合同:

发布http://localhost:8080/api/contracts{“name”：“contract1”}

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"
    }
  }
}

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"
    }
  }
}