Spring Data Rest - 无法更新（PATCH）引用另一个实体的子实体列表

Question

我有三个实体：父级、其子级和一些参考：

家长

@Entity
@Table(name = "parents")
public class Parent extends LongId {

    @NonNull
    @Column(nullable = false)
    private String name = "Undefine";

    @NonNull
    @OneToMany(cascade = MERGE)
    private List<Child> children = new ArrayList<>();
}

孩子

@Entity
@Table(name = "children")
public class Child extends LongId {

    @NonNull
    @Column(nullable = false)
    private String name;

    @NonNull
    @ManyToOne(optional = false)
    private Reference reference;
}

参考

@Entity
@Table(name = "references")
public class Reference extends LongId {

    @NotEmpty
    @Column(nullable = false)
    @Length(min = 3)
    @NonNull
    private String description;
}

和他们的存储库：

@RepositoryRestResource
public interface ParentRepo extends JpaRepository<Parent, Long> {
}

@RepositoryRestResource
public interface ChildRepo extends JpaRepository<Child, Long> {
}

@RepositoryRestResource
public interface ReferenceRepo extends JpaRepository<Reference, Long> {
}

之前，我坚持了几个孩子的参考。然后我用一个孩子创建了一个新的 Parent：

POST http://localhost:8080/api/parents
{
    "name" : "parent2",
    "children" : [
        "http://localhost:8080/api/children/3"
        ]
}

并已成功获得状态 201 Created。但是当我尝试将另一个孩子添加到parent2 时（用 PATCH 更新它）：

PATCH http://localhost:8080/api/parents/2
{
    "name" : "parent2",
    "children" : [
        "http://localhost:8080/api/children/3",
        "http://localhost:8080/api/children/4"
        ]
}

我有一个错误：

{
  "cause": {
    "cause": null,
    "message": "Can not construct instance of restsdemo.domain.entity.Child: no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/api/children/4')\n at [Source: N/A; line: -1, column: -1]"
  },
  "message": "Could not read payload!; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of restsdemo.domain.entity.Child: no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/api/children/4')\n at [Source: N/A; line: -1, column: -1]"
}

如果我从 Child 中删除指向 Reference 实体的链接：

POST http://localhost:8080/api/parents
{
    "name" : "parent2",
    "children" : [
        "http://localhost:8080/api/children/3"
        ]
}

一切正常 - child4成功添加到parent2。

如果子实体引用了另一个实体，您能否指出如何正确更新子实体列表？

这个例子的回购在这里：https : //github.com/Cepr0/restdemo

Answer 1

我简直不敢相信！我向 Child 添加了一个带有 String 参数的空构造函数，一切正常！

@Entity
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Table(name = "children")
public class Child extends LongId {

    @NonNull
    @Column(nullable = false)
    private String name;

    @NonNull
    @ManyToOne(optional = false)
    private Reference reference;

    public Child(String reference) {
    }
}

谁能解释为什么它有效？