用jackson将双向JPA实体序列化为JSON [英] Serialize bi-directional JPA entities to JSON with jackson

问题描述

我有以下类：

  import com.fasterxml.jackson.annotation。*; 
 import javax.persistence。*; 
 import java.util.Set; 
 
 @JsonInclude（JsonInclude.Include.NON_NULL）
 @JsonIgnoreProperties（ignoreUnknown = true）
 @JsonIdentityInfo（generator = ObjectIdGenerators.PropertyGenerator.class）
 @Entity 
 public class Parent {
 @Id 
 @GeneratedValue（strategy = GenerationType.IDENTITY）
 private Long id; 
私人字符串名称; 
 
 @JsonManagedReference 
 @OneToMany（mappedBy =parent，cascade = CascadeType.ALL，fetch = FetchType.EAGER）
 private Set< Child>儿童; 
 
 // Getters and setters 
} 
  

和 p>

  import com.fasterxml.jackson.annotation。*; 
 import javax.persistence。*; 
 import java.util.HashSet; 
 import java.util.Set; 
 
 @JsonInclude（JsonInclude.Include.NON_NULL）
 @JsonIgnoreProperties（ignoreUnknown = true）
 @JsonIdentityInfo（generator = ObjectIdGenerators.IntSequenceGenerator.class）
 @Entity 
 public class Child {
 @Id 
 @GeneratedValue（strategy = GenerationType.IDENTITY）
 private Long id; 
私人字符串名称; 
 
 @JsonBackReference 
 @ManyToOne 
 @JoinColumn（name =parentId）
私有父母; 
 
 //获得者和设定者
} 
  

我是使用POJO映射从模型序列化到JSON。当我序列化一个Parent对象时，我得到以下JSON：

  {
id：1，
name：John Doe，
children：[
 {
id：1，
name：child1
} ，{
id：2，
name：child2
} 
] 
} 
  

但是当我序列化一个孩子时，我得到以下JSON：

 id：1，
name：child1
} 
  

缺少对父项的引用。
有没有办法解决这个问题？

解决方案

我想你必须在@JsonIdentityInfo和@ JsonBackReference / @ JsonManagedReference。

我会去：@JsonIdentityInfo（generator = ObjectIdGenerators.PropertyGenerator.class，property =id）在你的实体上，删除@ JsonBackReference / @JsonManagedReference对。

在要排除的字段上添加@JsonIgnore。

I'm using Jackson to serialize my JPA model into JSON.

I have the following classes:

import com.fasterxml.jackson.annotation.*;
import javax.persistence.*;
import java.util.Set;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class)
@Entity
public class Parent {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;
  private String name;

  @JsonManagedReference
  @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
  private Set<Child> children;

  //Getters and setters
}

and

import com.fasterxml.jackson.annotation.*;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class)
@Entity
public class Child {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;
  private String name;

  @JsonBackReference
  @ManyToOne
  @JoinColumn(name = "parentId")
  private Parent parent;

  //Getters and setters
}

I'm using the POJO mapping to serialize from model to JSON. When I serialize a Parent object I get the following JSON:

{
  "id": 1,
  "name": "John Doe",
  "children": [
    {
      "id": 1,
      "name": "child1"
    },{
      "id": 2,
      "name": "child2"
    }
  ]
}

But when I serialize a Child I get the following JSON:

{
  "id": 1,
  "name": "child1"
}

The reference to the parent is missing. Is there a way to solve this?

解决方案

I think you have to chose between the @JsonIdentityInfo and the @JsonBackReference/@JsonManagedReference.

I would go with : @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property="id") on your entities, removes @JsonBackReference/@JsonManagedReference pairs.

And add @JsonIgnore on the fields you want to exclude.

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