一、List转换成json字符串
这个比较简单，导入gson-x.x.jar，
List<User> users = new ArrayList<User>(); Gson gson = new Gson(), String json = gson.toJson(users)
返回的就是json格式字符串
[{"id":2,"userName":"liuwenlei","isLogin":2},{"id":3,"userName":"liuxinglei","isLogin":2}]
二、json字符串转换成List
需要导入的jar包有：
json-lib-2.4-jdk15.jar
commons-beanutils-1.8.3.jar
ezmorph-1.0.6.jar
String jsonString = "[{\"id\":2,\"userName\":\"liuwenlei\",\"isLogin\":2},{\"id\":3,\"userName\":\"liuxinglei\",\"isLogin\":2}]";
JSONArray gsonarr = JSONArray.fromObject(jsonString);
List<User> users = JSONArray.toList(gsonarr, User.class);
System.out.println(users);
输出的结果为
[User [id=2, userName=liuwenlei, isLogin=2], User [id=3, userName=liuxinglei, isLogin=2]]