在使用json的时候，麻烦的是要吧java后台的各种数据转化为json格式输出，下面列举几种情况。
首先你要引入的包有：六个常用的包 1）commons-logging-1.0.4.jar、2）commons-lang-2.3.jar、3）commons-collections-3.2.jar 、4）commons-beanutils-1.7.0.jar、5）json-lib-2.2.1-jdk15.jar、6）ezmorph-1.0.4.jar
如果用到框架还要引用struts的插件jsonplugin.jar
普通JavaBean转成json格式
1.转成JSONArray类型
User user = new User();
user.setUsername("红领巾");
user.setPassword("1234");
JSONArray json = JSONArray.fromObject(user);
System.out.println(json);//[{"password":"1234","username":"红领巾"}]
response.getWriter().print(json.toString());
2.转成JSONObject类型
JSONObject jsonObj = JSONObject.fromObject(user);
System.out.println(jsonObj);//{"password":"1234","username":"cxl"}
response.getWriter().print(jsonObj);
在js文件取数据
alert(data.username);
alert(data.password);
List转成json格式
List<User> users = new ArrayList<User>();
User user = new User();
user.setUsername("cxl");
user.setPassword("1234");
User u = new User();
u.setUsername("lhl");
u.setPassword("1234");
users.add(user);
users.add(u);
1.转成JSONArray类型
JSONArray json = JSONArray.fromObject(users);
System.out.println(json.toString());
//[{"password":"1234","username":"cxl"},
{"password":"1234","username":"lhl"}]
response.getWriter().print(json.toString());
js中取数据：alert(alert(data[0].username));
2.转成JSONObject类型
不可直接使用JSONObject jsonObj = JSONObject.fromObject(users);
可通过下列方式
JSONObject jsonObj = new JSONObject();
jsonObj.put("users", users);
jsonObj.put("u", u);
System.out.println(jsonObj);
{"users":[{"password":"1234","username":"cxl"},
{"password":"1234","username":"lhl"}],
"u":{"password":"1234","username":"lhl"}}
response.getWriter().print(jsonObj);
js中取数据：alert(data.users[0].username);
alert(data.u[0].username);
Map转成json格式
Map<String,Object> map = new HashMap<String,Object>();
map.put("users", users);
map.put("u", u);
1.转成JSONArray类型
JSONArray json = JSONArray.fromObject(map);
System.out.println(json.toString());// [{"users":
[{"password":"1234","username":"cxl"},
{"password":"1234","username":"lhl"}],"u":
{"password":"1234","username":"lhl"}}]
response.getWriter().print(json.toString);
js中取数据：alert(data[0].users[0].username);
2.转成JSONObject类型
JSONObject json = JSONObject.fromObject(map);
System.out.println(json);//
{"user":[{"password":"1234","username":"cxl"},
{"password":"1234","username":"lhl"}],"u":
{"password":"1234","username":"lhl"}}
response.getWriter().print(json);
js中取数据：alert(data.user[0].username);
不要问我是谁，请叫我红领巾