重复引用
- 定义
一个对象对另外一个对象
多个字段重复引用
集合字段重复引用.
public class JsonTest {
/**
* 学生
*/
private static class Student {
/**
* 姓名
*/
private String name;
public Student(String name) {
this.name = name;
}
/**
* Getter method for property name.
*
* @return property value of name
*/
public String getName() {
return name;
}
/**
* Setter method for property counterType.
*
* @param name value to be assigned to property <tt>name</tt>
*/
public void setName(String name) {
this.name = name;
}
}
private static class Teacher {
/**
* 姓名
*/
private String name;
/**
* 学生列表
*/
private List<Student> studentList = Lists.newArrayList();
/**
* 新增学生
* @param student
*/
public void addStudent(Student student) {
studentList.add(student);
}
/**
* Getter method for property name.
*
* @return property value of name
*/
public String getName() {
return name;
}
/**
* Setter method for property counterType.
*
* @param name value to be assigned to property <tt>name</tt>
*/
public void setName(String name) {
this.name = name;
}
/**
* Getter method for property studentList.
*
* @return property value of studentList
*/
public List<Student> getStudentList() {
return studentList;
}
/**
* Setter method for property counterType.
*
* @param studentList value to be assigned to property <tt>studentList</tt>
*/
public void setStudentList(List<Student> studentList) {
this.studentList = studentList;
}
}
public static void main(String[] args) {
Teacher teacher = new Teacher();
Student student = new Student("张三");
teacher.addStudent(student);
teacher.addStudent(student);
System.out.println(JSON.toJSONString(teacher));
}
}
结果:
{"studentList":[{"name":"张三"},{"$ref":"$.studentList[0]"}]}
循环引用
- 定义
对象A引用对象B, 对象B引用对象A 出现你中有,我中有你现象.
private static class Item{
/**
* 商品Id
*/
private String itemId;
/**
* 关联订单
*/
private Order order;
/**
* Getter method for property itemId.
*
* @return property value of itemId
*/
public String getItemId() {
return itemId;
}
/**
* Setter method for property counterType.
*
* @param itemId value to be assigned to property <tt>itemId</tt>
*/
public void setItemId(String itemId) {
this.itemId = itemId;
}
/**
* Getter method for property order.
*
* @return property value of order
*/
public Order getOrder() {
return order;
}
/**
* Setter method for property counterType.
*
* @param order value to be assigned to property <tt>order</tt>
*/
public void setOrder(Order order) {
this.order = order;
}
}
private static class Order{
/**
* 订单Id
*/
private String orderId;
/**
* 关联商品
*/
private Item item;
/**
* Getter method for property orderId.
*
* @return property value of orderId
*/
public String getOrderId() {
return orderId;
}
/**
* Setter method for property counterType.
*
* @param orderId value to be assigned to property <tt>orderId</tt>
*/
public void setOrderId(String orderId) {
this.orderId = orderId;
}
/**
* Getter method for property item.
*
* @return property value of item
*/
public Item getItem() {
return item;
}
/**
* Setter method for property counterType.
*
* @param item value to be assigned to property <tt>item</tt>
*/
public void setItem(Item item) {
this.item = item;
}
}
public static void main(String[] args) {
Order order = new Order();
Item item = new Item();
item.setItemId("itemId");
item.setOrder(order);
order.setItem(item);
order.setOrderId("orderId");
System.out.println(JSON.toJSONString(item));
System.out.println(JSON.toJSONString(order));
}
结果:
{"itemId":"itemId","order":{"item":{"$ref":".."},"orderId":"orderId"}}
{"item":{"itemId":"itemId","order":{"$ref":".."}},"orderId":"orderId"}
解决方案
- 避免循环引用这种情形出现.
- 不对循环引用的字段进行序列化.
- 编码时 使用新对象 或者 新集合 赋值,不要使用同一个对象.
- 不要关闭FastJson 引用检测机制.如果为了避免在重复引用时显示$ref而关闭它，会有很大可能导致循环引用时发生StackOverflowError异常
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