Gson入门示例

简介

Gson 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. 

示例

本文主要涉及如下内容：

1、JSON字符串转对象；
2、JSON字符串转集合；
3、对象转JSON字符串；

App.java

package demo.gson;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import demo.gson.entity.User;

import java.util.ArrayList;
import java.util.List;

public class App {

    public static void main(String[] args) {
        App.testConvertObjectToJson();
        App.testConvertListToJson();
        App.testConvertJsonToObject();
        App.testConvertJsonToList();
    }

    private static void testConvertObjectToJson() {
        System.out.println("== testConvertObjectToJson ==");
        User user = new User("1", "0001", "程序员", "111", "[e-mail]");
        System.out.println(new Gson().toJson(user));
        // 结果：{"id":"1","usercode":"0001","username":"程序员","password":"111","email":"[e-mail]"}
    }

    private static void testConvertListToJson() {
        System.out.println("== testConvertListToJson ==");
        List<User> list = new ArrayList<>();
        list.add(new User("1", "0001", "程序员1", "111", "[e-mail]"));
        list.add(new User("2", "0002", "程序员2", "222", "[e-mail]"));
        System.out.println(new Gson().toJson(list));
        // 结果：[{"id":"1","usercode":"0001","username":"程序员1","password":"111","email":"[e-mail]"},{"id":"2","usercode":"0002","username":"程序员2","password":"222","email":"[e-mail]"}]
    }

    private static void testConvertJsonToObject() {
        System.out.println("== testConvertJsonToObject ==");
        String json = "{\"id\":\"1\",\"usercode\":\"0001\",\"username\":\"程序员\",\"password\":\"111\",\"email\":\"[e-mail]\"}";
        System.out.println(new Gson().fromJson(json, User.class));
        /*
        结果：
        User[id='1', usercode='0001', username='程序员', password='111', email='[e-mail]', createTime=null]
         */
    }

    private static void testConvertJsonToList() {
        System.out.println("== testConvertJsonToList ==");
        String json = "[{\"id\":\"1\",\"usercode\":\"0001\",\"username\":\"程序员1\",\"password\":\"111\",\"email\":\"[e-mail]\"},{\"id\":\"2\",\"usercode\":\"0002\",\"username\":\"程序员2\",\"password\":\"222\",\"email\":\"[e-mail]\"}]";
        List<User> list = new Gson().fromJson(json, new TypeToken<List<User>>(){}.getType());
        list.forEach(user -> System.out.println(user));
        /*
        结果：
        User[id='1', usercode='0001', username='程序员1', password='111', email='[e-mail]', createTime=null]
        User[id='2', usercode='0002', username='程序员2', password='222', email='[e-mail]', createTime=null]
         */
    }
}

User.java

package demo.gson.entity;

import java.util.Date;
import java.util.StringJoiner;

/**
 * @Description: 用户
 */
public class User {

    /**
     * 主键
     */
    private String id;
    /**
     * 用户编码
     */
    private String usercode;
    /**
     * 用户名称
     */
    private String username;
    /**
     * 密码
     */
    private String password;
    /**
     * 邮箱
     */
    private String email;
    /**
     * 创建时间
     */
    private Date createTime;

    public User() {}

    public User(String id, String usercode, String username, String password, String email) {
        this.id = id;
        this.usercode = usercode;
        this.username = username;
        this.password = password;
        this.email = email;
    }

    public String getId() {
        return id;
    }

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

    public String getUsercode() {
        return usercode;
    }

    public void setUsercode(String usercode) {
        this.usercode = usercode;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    @Override
    public String toString() {
        return new StringJoiner(", ", User.class.getSimpleName() + "[", "]")
                .add("id='" + id + "'")
                .add("usercode='" + usercode + "'")
                .add("username='" + username + "'")
                .add("password='" + password + "'")
                .add("email='" + email + "'")
                .add("createTime=" + createTime)
                .toString();
    }
}

链接

• Gson官网