fastjson解析json时报错 class not has default constructor

来源：互联网发布：java中的静态变量编辑：程序博客网时间：2024/06/10 07:30

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@15f550aProcess finished with exit code 0

0 0