Fastjson

Fastjson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object.

Fastjson Features:

Provide best performance in server side and android client

Provide simple toJSONString() and parseObject() methods to convert Java objects to JSON and vice-versa

Allow pre-existing unmodifiable objects to be converted to and from JSON

Extensive support of Java Generics

Parsing JSON with Fastjson

You can look at example in Fastjson library

Encode

import com.alibaba.fastjson.JSON;

Group group = new Group();
group.setId(0L);
group.setName("admin");

User guestUser = new User();
guestUser.setId(2L);
guestUser.setName("guest");

User rootUser = new User();
rootUser.setId(3L);
rootUser.setName("root");

group.addUser(guestUser);
group.addUser(rootUser);

String jsonString = JSON.toJSONString(group);

System.out.println(jsonString);

Output

{"id":0,"name":"admin","users":[{"id":2,"name":"guest"},{"id":3,"name":"root"}]}

Decode

String jsonString = ...;
Group group = JSON.parseObject(jsonString, Group.class);

Group.java

public class Group {

    private Long id;
    private String name;
    private List<User> users = new ArrayList<User>();

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

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

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

    public void addUser(User user) {
        users.add(user);
    }
}

User.java

public class User {

    private Long   id;
    private String name;

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

Convert the data of type Map to JSON String

Code

   Group group = new Group();
    group.setId(1);
    group.setName("Ke");

    User user1 = new User();
    user1.setId(2);
    user1.setName("Liu");

    User user2 = new User();
    user2.setId(3);
    user2.setName("Yue");
    group.getList().add(user1);
    group.getList().add(user2);

    Map<Integer, Object> map = new HashMap<Integer,Object>();
    map.put(1, "No.1");
    map.put(2, "No.2");
    map.put(3, group.getList());

    String jsonString = JSON.toJSONString(map);
    System.out.println(jsonString);

Output

{1:"No.1",2:"No.2",3:[{"id":2,"name":"Liu"},{"id":3,"name":"Yue"}]}

Syntax

• Object parse(String text)
• JSONObject parseObject(String text)
• T parseObject(String text, Class clazz)
• JSONArray parseArray(String text)
• List parseArray(String text, Class clazz)
• String toJSONString(Object object)
• String toJSONString(Object object, boolean prettyFormat)
• Object toJSON(Object javaObject)