方式一： json-lib

                <dependency>
			<groupId>net.sf.json-lib</groupId>
			<artifactId>json-lib</artifactId>
			<version>2.4</version>
			<classifier>jdk15</classifier>
		</dependency>

import java.util.HashMap;

import java.util.Map;

 

import net.sf.json.JSONObject;

 

public class test{

	  public static void main(String[] args) {

	        Map map = new HashMap();

	        map.put("test", "test1");

	        JSONObject jsonObject = JSONObject.fromObject(map);

	        System.out.println("输出的结果是：" + jsonObject);

	        //3、将json对象转化为json字符串

	        String result = jsonObject.toString();

	        System.out.println(result);

	    }

}

json-lib是一个比较老的解决方案，近几年都没有升级过，它的适用环境是JDK1.5，使用JDK1.6就有可能会报错。所以配置上加入classifier-jdk15来解决这个问题。 

方式二：alibaba

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.41</version>
</dependency>

  public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("test", "test1");
        map.put("target", "from");
        String jsonString = JSONObject.toJSONString(map);
        System.out.println(jsonString);
        Map<String, String> map2 = JSONObject.parseObject(jsonString, Map.class);
        System.out.println(map2.get("test"));
    }

 方式三：google–Gson

<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.3.1</version>
</dependency>

public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("test", "test1");
        map.put("target", "from");
       
        Gson gson = new Gson();
        String gsonStr = gson.toJson(map);
        System.out.println(gsonStr);
        Map map3 = gson.fromJson(gsonStr, Map.class);
        System.out.println(map3.get("target"));
    }