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 (opens new window)

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)