Gson应用：利用map和list来拼装Json消息

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import com.google.gson.Gson;

 public class GsonTest {

     public static void main(String[] args) {

         Gson g = new Gson();
         Map<String,Object> map = new HashMap<String,Object>();
         //添加两个普通节点
         map.put("a","1");
         map.put("b",2);

         //添加一个list1 => "list1":[{"c":"3","d":4}]
         Map<String,Object> m5 = new HashMap<String,Object>();
         List<Object> l = new ArrayList<Object>();
         m5.put("c","3");
         m5.put("d",4);
         l.add(m5);
         map.put("list1",l);

         //添加一个map1 =>"map1":{"e":"5","f":"6"}
         Map<String,Object> m2 = new HashMap<String,Object>();
         m2.put("e","5");
         m2.put("f","6");
         map.put("map1",m2);

         //添加一个list2 => "list2":[{"g":"7","h":8},{"g":"9","h":10}]
         List<Object> l2 = new ArrayList<Object>();
         Map<String,Object> m3 = new HashMap<String,Object>();
         Map<String,Object> m4 = new HashMap<String,Object>();
         m3.put("g","7");
         m3.put("h",8);
         m4.put("g","9");
         m4.put("h",10);
         l2.add(m3);
         l2.add(m4);
         map.put("list2",l2);

         //添加一个map2 => "map2":{"i":"5","j":[{"j":"5","k":"5"}],"l":{"j":"5","k":"5"}}
         Map<String,Object> m6 = new HashMap<String,Object>();
         List<Object> l3 = new ArrayList<Object>();
         Map<String,Object> m7 = new HashMap<String,Object>();
         m6.put("i","5");

         m7.put("j","5");
         m7.put("k","5");
         m6.put("l",m7);

         l3.add(m7);
         m6.put("j",l3);
         map.put("map2",m6);

         //转换成JSON格式内容
         String s = g.toJson(map);
         System.out.println(s);

     }

 }

输出

{"list1":[{"c":"3","d":4}],"a":"1","b":2,"map2":{"i":"5","j":[{"j":"5","k":"5"}],"l":{"j":"5","k":"5"}},"map1":{"e":"5","f":"6"},"list2":[{"g":"7","h":8},{"g":"9","h":10}]}

 {
     "list1":[
         {
             "c":"3",
             "d":4
         }
     ],
     "a":"1",
     "b":2,
     "map2":{
         "i":"5",
         "j":[
             {
                 "j":"5",
                 "k":"5"
             }
         ],
         "l":{
             "j":"5",
             "k":"5"
         }
     },
     "map1":{
         "e":"5",
         "f":"6"
     },
     "list2":[
         {
             "g":"7",
             "h":8
         },
         {
             "g":"9",
             "h":10
         }
     ]
 }