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

傷城~ 2022-07-19 00:27 215阅读 0赞

## 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：

## 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