fastjson解析json时报错 class not has default constructor

在序列化用alibaba的json包把对象进行序列化的时候，总是报错

Exception in thread "main" com.alibaba.fastjson.JSONException: default constructor not found. class com.mex.test.redis.Person

Person类

public class Person {

private String name;
private int age;

public Person(String name, int age) {
this.name = name;
this.age = age;
}

public String getName() {
return name;
}

public int getAge() {
return age;
}

public void setName(String name) {
this.name = name;
}

public void setAge(int age) {
this.age = age;
}
}

User类

public class User {

private String id;
private List<Person> users = new ArrayList<Person>();

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public List<Person> getUsers() {
return users;
}

public void setUsers(List<Person> users) {
this.users = users;
}
}

测试类

public class SerializationTest {

public static void main(String[] args) {

User user = new User();
user.setId("1001");
Person p1 = new Person("xiaoming",23);
Person p2 = new Person("jack",34);
ArrayList<Person> pList = Lists.newArrayList();
pList.add(p1);
pList.add(p2);

user.setUsers(pList);

// 序列化
String s = JSON.toJSONString(user);
System.out.println(s);

User user1 = JSON.parseObject(s, User.class);
System.out.println(user1);
}
}

查找了半天的资料，fastJson在反序列化的时候需要调用对象的默认构造方法，如果该对象之中还包含其他的对象，那么都需要创建默认的无参构造方法。

解决方案：将User的默认无参构造和Person的默认无参构造补充到类中，即可。

public User() {
}

public Person() {
}

打印出来的信息为：

{"id":"1001","users":[{"age":23,"name":"xiaoming"},{"age":34,"name":"jack"}]}
com.mex.test.redis.User@15f550a

Process finished with exit code 0