json对象和java对象的相互转换方法(json-lib、jackson、fastjson、gson)

一 使用json-lib包下的JSONObject和JSONArray转换

代码如下：

package com.test.test;

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

import com.cn.entity.User;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
/**
 * JSONObject和JSONArray
 * @author sun.kai
 * 2016年8月7日
 */
public class TestJsonOne {

    public static void main(String[] args){
        long time1 = System.currentTimeMillis();
//        Map<String, Object> param = new HashMap<String,Object>();
//        param.put("id", 1);
//        param.put("userName", "admin管理员");
//        param.put("password", "admin123456");
//        param.put("age", 25);
//        JSONObject jsonObject = JSONObject.fromObject(param);
//        System.out.println(jsonObject);
//        JSONArray jsonArray = JSONArray.fromObject(param);
//        System.out.println(jsonArray);
        List<User> list = new ArrayList<User>();
        User user1 = new User();
        user1.setId(1);
        user1.setUserName("admin管理员");
        user1.setPassword("admin123456");
        user1.setAge(25);
        testJsonObject(user1);
        list.add(user1);
        User user2 = new User();
        user2.setId(2);
        user2.setUserName("海角七号");
        user2.setPassword("海角七号123456");
        user2.setAge(26);
        list.add(user2);
        testJsonArray(list);
        long time2 = System.currentTimeMillis();
        System.out.println(time2-time1);
    }
    @SuppressWarnings("static-access")
    public static void testJsonObject(User user){
        System.out.println("JSONObject测试");
        /*
         * java对象转换成json对象
         */
        JSONObject jsonObject1 = JSONObject.fromObject(user);
        /*
         * json对象转成字符串
         */
        String jsonsString1 = jsonObject1.toString();
        System.out.println(jsonObject1);
        System.out.println(jsonsString1);
        
        String jsonString2 = "{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}";
        /*
         * 字符串转成json对象
         */
        JSONObject jsonObject2 = JSONObject.fromObject(jsonString2);
        /*
         * json对象转成java对象
         */
        User user2 = (User) jsonObject2.toBean(jsonObject2,User.class);
        System.out.println(user2.getUserName());
        /*
         * 获取json对象中的json对象数组
         */
        String jsonString3 = "{"abc":[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},"
                + "{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}"
                + "]}";
        //字符串转成json对象
        JSONObject jsonObject3 = JSONObject.fromObject(jsonString3);
        //获取json对象中的json对象数组
        JSONArray jsonArray = jsonObject3.getJSONArray("abc");
        System.out.println(jsonArray.toString());
    }
    @SuppressWarnings("unchecked")
    public static void testJsonArray(List<User> userList){
        System.out.println("JSONArray测试");
        /*
         * java对象列表转换为json对象数组
         */
        JSONArray jsonArray1 = JSONArray.fromObject(userList);
        /*
         * json对象数组转成字符串
         */
        String arrayString1 = jsonArray1.toString();
        System.out.println(jsonArray1);
        System.out.println(arrayString1);
        
        String arrayString2 = "[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]";
        /*
         * 字符串转成json对象数组
         */
        JSONArray jsonArray2 = JSONArray.fromObject(arrayString2);
        /*
         * json对象数组转成java对象
         */
        List<User> users = (List<User>) JSONArray.toCollection(jsonArray2, User.class);
        for(User user : users){
            System.out.println(user.getUserName());
        }
        /*
         * 循环json对象数组，获取json对象
         */
        for(int i = 0;i<jsonArray2.size();i++){
            JSONObject jsonObject = jsonArray2.getJSONObject(i);
            System.out.println(jsonObject);
        }
    }
}

User实体类代码：

package com.cn.entity;

import java.io.Serializable;

public class User implements Serializable{
    private static final long serialVersionUID = -154635138564326678L;

    private Integer id;

    private String userName;

    private String password;

    private Integer age;

    public Integer getId() {
        return id;
    }

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

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName == null ? null : userName.trim();
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password == null ? null : password.trim();
    }

    public Integer getAge() {
        return age;
    }

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

执行后的结果：

JSONObject测试
{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}
{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}
admin管理员
[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]
JSONArray测试
[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]
[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]
admin管理员
海角七号
{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}
{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}
686

二 使用jackson-databind包下的ObjectMapper

代码如下：

package com.test.test;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import com.cn.entity.User;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
/**
 * jackson是spring mvc内置的json转换工具
 * @author sun.kai
 * 2016年8月7日
 */
public class TestJsonTwo {
    public static void main(String[] args) throws JsonProcessingException{
        long time1 = System.currentTimeMillis();
        List<User> users = new ArrayList<User>();
        User user1 = new User();
        user1.setId(1);
        user1.setUserName("admin管理员");
        user1.setPassword("admin123456");
        user1.setAge(25);
        users.add(user1);
        User user2 = new User();
        user2.setId(2);
        user2.setUserName("海角七号");
        user2.setPassword("海角七号123456");
        user2.setAge(26);
        users.add(user2);
        try {
            testObjectMapper(users);
        } catch (IOException e) {
            e.printStackTrace();
        }
        long time2 = System.currentTimeMillis();
        System.out.println(time2-time1);
    }
    
    public static void testObjectMapper(List<User> users) throws IOException{
        ObjectMapper mapper = new ObjectMapper();
        /*
         * java对象是一个集合
         * 转成的字符串是json对象数组
         */
        String mapperString1 = mapper.writeValueAsString(users);
        System.out.println(mapperString1);
        /*
         * java对象不是一个集合
         * 转成json对象字符串
         */
        String mapperString2 = mapper.writeValueAsString(users.get(0));
        System.out.println(mapperString2);
        /*
         * json对象数组字符串转java对象集合
         */
        String jsonString1 = "[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]";
        User[] userArray = mapper.readValue(jsonString1, User[].class);
        List<User> userList = Arrays.asList(userArray);
        for (User user : userList) {
            System.out.println(user.getUserName());
        }
        /*
         * json对象字符串转java对象
         */
        String jsonString2 = "{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}";
        User user = mapper.readValue(jsonString2, User.class);
        System.out.println(user.getUserName());
    }
}

执行后的结果：

[{"id":1,"userName":"admin管理员","password":"admin123456","age":25},{"id":2,"userName":"海角七号","password":"海角七号123456","age":26}]
{"id":1,"userName":"admin管理员","password":"admin123456","age":25}
admin管理员
海角七号
admin管理员
784

三 使用fastjson

代码如下：

package com.test.test;
import com.cn.entity.User;

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

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.TypeReference;
/**
 * fastjson是阿里做的国有开源Java工具包
 * @author sun.kai
 * 2016年8月7日
 */
public class TestJsonThree {
    
    public static void main(String[] args){
        long time1 = System.currentTimeMillis();
        List<User> users = new ArrayList<User>();
        User user1 = new User();
        user1.setId(1);
        user1.setUserName("admin管理员");
        user1.setPassword("admin123456");
        user1.setAge(25);
        users.add(user1);
        User user2 = new User();
        user2.setId(2);
        user2.setUserName("海角七号");
        user2.setPassword("海角七号123456");
        user2.setAge(26);
        users.add(user2);
        testFastjson(users);
        long time2 = System.currentTimeMillis();
        System.out.println(time2-time1);
    }
    
    @SuppressWarnings("unchecked")
    public static void testFastjson(List<User> users){
        /*
         * java对象是一个集合
         * 转成的字符串是json对象数组
         */
        String fastjsonString1 = JSON.toJSONString(users);
        System.out.println(fastjsonString1);
        /*
         * java对象不是一个集合
         * 转成json对象字符串
         */
        String fastjsonString2 = JSON.toJSONString(users.get(0));
        System.out.println(fastjsonString2);
        /*
         * json对象数组字符串转java对象集合
         */
        String jsonString1 = "[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]";
        List<User> userList = JSON.parseArray(jsonString1, User.class);
        for (User user : userList) {
            System.out.println(user.getUserName());
        }
        /*
         * json对象数组字符串转Map集合
         */
        List<Map<String, Object>> maps = JSON.parseObject(jsonString1,new TypeReference<List<Map<String,Object>>>(){});
        System.out.println(maps);
        for (Map<String, Object> map : maps) {
            System.out.println(map.get("userName"));
        }
        /*
         * json对象字符串转java对象
         */
        String jsonString2 = "{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}";
        User user = JSON.parseObject(jsonString2, User.class);
        System.out.println(user.getUserName());
        /*
         * json对象字符串转Map
         */
        Map<String, Object> map = JSON.parseObject(jsonString2, Map.class);
        System.out.println(map);
        System.out.println(map.get("userName"));
    }
}

执行结果：

[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]
{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}
admin管理员
海角七号
[{id=1, age=25, userName=admin管理员, password=admin123456}, {id=2, age=26, userName=海角七号, password=海角七号123456}]
admin管理员
海角七号
admin管理员
{id=1, age=25, userName=admin管理员, password=admin123456}
admin管理员
338

四 使用Google的Gson

代码如下：

package com.test.test;
import com.cn.entity.User;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
 * google的gson
 * https://mvnrepository.com/artifact/com.google.code.gson/gson
 * @author sun.kai
 * 2016年8月7日
 */
public class TestJsonFour {
    public static void main(String[] args){
        long time1 = System.currentTimeMillis();
        List<User> users = new ArrayList<User>();
        User user1 = new User();
        user1.setId(1);
        user1.setUserName("admin管理员");
        user1.setPassword("admin123456");
        user1.setAge(25);
        users.add(user1);
        User user2 = new User();
        user2.setId(2);
        user2.setUserName("海角七号");
        user2.setPassword("海角七号123456");
        user2.setAge(26);
        users.add(user2);
        testGson(users);
        long time2 = System.currentTimeMillis();
        System.out.println(time2-time1);
    }
    
    @SuppressWarnings("unchecked")
    public static void testGson(List<User> users){
        /*
         * 创建Gson对象
         */
        Gson gson = new Gson();
        /*
         * 获得泛型参数的类型
         */
        java.lang.reflect.Type type = new TypeToken<List<User>>() {}.getType();
        /*
         * java对象是一个集合
         * 转成的字符串是json对象数组
         */
        String gsonString1 = gson.toJson(users);
        System.out.println(gsonString1);
        /*
         * java对象不是一个集合
         * 转成json对象字符串
         */
        String gsonString2 = gson.toJson(users.get(0));
        System.out.println(gsonString2);
        /*
         * json对象数组字符串转java对象集合
         */
        String jsonString1 = "[{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"},{"age":26,"id":2,"password":"海角七号123456","userName":"海角七号"}]";
        List<User> userList = gson.fromJson(jsonString1, type);
        for (User user : userList) {
            System.out.println(user.getUserName());
        }
        /*
         * json对象数组字符串转Map集合
         */
        List<Map<String, Object>> maps = gson.fromJson(jsonString1,new TypeToken<List<Map<String, Object>>>() {}.getType());
        System.out.println(maps);
        for (Map<String, Object> map : maps) {
            System.out.println(map.get("userName"));
        }
        /*
         * json对象字符串转java对象
         */
        String jsonString2 = "{"age":25,"id":1,"password":"admin123456","userName":"admin管理员"}";
        User user = gson.fromJson(jsonString2, User.class);
        System.out.println(user.getUserName());
        /*
         * json对象字符串转Map
         */
        Map<String, Object> map = gson.fromJson(jsonString2, Map.class);
        System.out.println(map);
        System.out.println(map.get("userName"));
    }
}

执行结果：

[{"id":1,"userName":"admin管理员","password":"admin123456","age":25},{"id":2,"userName":"海角七号","password":"海角七号123456","age":26}]
{"id":1,"userName":"admin管理员","password":"admin123456","age":25}
admin管理员
海角七号
[{age=25.0, id=1.0, password=admin123456, userName=admin管理员}, {age=26.0, id=2.0, password=海角七号123456, userName=海角七号}]
admin管理员
海角七号
admin管理员
{age=25.0, id=1.0, password=admin123456, userName=admin管理员}
admin管理员
336