如何使用 JSON-B(Java API for JSON Binding)序列化循环引用的对象

Question

我正在使用JSON-B将对象输出到json，并且对象中有一个循环引用(请不要要求我删除循环引用(，示例代码如下

Person 类包含属性列表 和属性类引用回形成循环引用的人。

在第一次打印中可以输出json，但是在第二次打印语句中，由于触摸对象的循环引用而导致堆栈溢出错误，我不想使用@JsonbTransient忽略其中任何一个，我该如何解决这个问题？

我期待 json 输出为

{"id":1,"name":"Jhon","propertyList":[{"person":1, "propertyName":"Palace"},{"person":1, "propertyName":"Apartment"}]}

示例代码：

import java.util.ArrayList;
import java.util.List;
import javax.json.bind.Jsonb;
import javax.json.bind.JsonbBuilder;
public class JsonTest {
public static void main(String[] args) throws InterruptedException {
Person person = new Person(1, "Jhon");
Jsonb jsonb = JsonbBuilder.create();
//no error as no property is added
System.out.println("jsonPerson without property: " + jsonb.toJson(person));
Property p1 = new Property();
p1.setPropertyName("Palace");
p1.setPerson(person);
Property p2 = new Property();
p2.setPropertyName("Apartment");
p2.setPerson(person);
person.getPropertyList().add(p1);
person.getPropertyList().add(p2);
/**
* stackoverflow here
*/
System.out.println("jsonPerson with property: " + jsonb.toJson(person));
}

public static class Property {
private Person person;
private String propertyName;
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public String getPropertyName() {
return propertyName;
}
public void setPropertyName(String propertyName) {
this.propertyName = propertyName;
}
}
public static class Person {
private int id;
public Person() {
super();
}
public Person(int id, String name) {
super();
this.id = id;
this.name = name;
}
private String name;
private List<Property> propertyList = new ArrayList<>();
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Property> getPropertyList() {
return propertyList;
}
public void setPropertyList(List<Property> propertyList) {
this.propertyList = propertyList;
}
}
}

Answer 1

最后，我放弃使用 JSON-B，转而使用 Jackson，使用注释@JsonIdentityInfo这是我的信息解决方案：

import java.util.ArrayList;
import java.util.List;
import javax.json.bind.Jsonb;
import javax.json.bind.JsonbBuilder;
import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JsonTest {
private static Person person = null;
private static List<Property> propertyList = new ArrayList<>();
public static void main(String[] args) throws Exception {
person = new Person(1, "Jhon");
propertyList.add(new Property(1, person, "Palace"));
propertyList.add(new Property(2, person, "Apartment"));
person.setPropertyList(propertyList);
jacksonTest();
//jsonbTest();
}
private static void jacksonTest()
throws Exception
{
String result = new ObjectMapper().writeValueAsString(person);
System.out.println("result: " + result);
}
private static void jsonbTest()
throws Exception
{
Jsonb jsonb = JsonbBuilder.create();
/**
* stackoverflow here
*/
System.out.println("jsonPerson with property: " + jsonb.toJson(person));
}
public static class Property extends BaseEntity {
private Person person;
private String propertyName;
public Property(int id, Person person, String propertyName) {
super();
setId(id);
this.person = person;
this.propertyName = propertyName;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public String getPropertyName() {
return propertyName;
}
public void setPropertyName(String propertyName) {
this.propertyName = propertyName;
}
}
public static class Person extends BaseEntity {
public Person() {
super();
}
public Person(int id, String name) {
super();
setId(id);
this.name = name;
}
private String name;
private List<Property> propertyList = new ArrayList<>();
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Property> getPropertyList() {
return propertyList;
}
public void setPropertyList(List<Property> propertyList) {
this.propertyList = propertyList;
}
}
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
public static abstract class BaseEntity {
private int id;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
}

杰克逊输出：

result: {"id":1,"name":"Jhon","propertyList":[{"id":1,"person":1,"propertyName":"Palace"},{"id":2,"person":1,"propertyName":"Apartment"}]}