JAVA array,map 转 json 字符串

你离开我真会死。 提交于 2019-12-18 15:23:03
  1. public class User {  
  2.       
  3.     private String username;  
  4.     private String password;  
  5.       
  6.     public String getUsername() {  
  7.         return username;  
  8.     }  
  9.     public void setUsername(String username) {  
  10.         this.username = username;  
  11.     }  
  12.     public String getPassword() {  
  13.         return password;  
  14.     }  
  15.     public void setPassword(String password) {  
  16.         this.password = password;  
  17.     }  
  18.       
  19. }  


普通JavaBean(以User为例)转成json格式 
1.转成JSONArray类型 
User user = new User(); 
user.setUsername("cxl"); 
user.setPassword("1234"); 
JSONArray json = JSONArray.fromObject(user); 
System.out.println(json);//[{"password":"1234","username":"cxl"}] 
response.getWriter().print(json.toString()); 
在js文件取数据 
$.getJSON("http://localhost:8080/jQueryDemo/servlet/UserServlet",null,function(data) { 
      alert(data[0].username); 
      alert(data[0].password); 
}); 
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); 

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