JSON基础知识总结

一、 总结

JSON对象是一个无序的"名称/值"对的集合
它开始于“{”，结束于“}”。每一个属性名和值间用“:”提示，属性间用“,”分隔。一个数组开始于"["，结束于"]"，值之间用","分隔。

数组和List转换为JSON用JSONArray.fromObject 
Map、bean、beans(保存在一个List中转换)转换为JSON用 JSONObject.fromObject

JSONObject.toBean(JSONObject类型,Class类型)  // 转换为对象(如自定义类对象，Map对象等)

 

 

JSON （JavaScript Object Notation）是一种轻量级的数据交换格式，非常适合于服务器与 JavaScript 的交互. 
JSON 是 JavaScript 原生格式，这意味着在 JavaScript 中处理 JSON 数据不需要任何特殊的 API 或工具包。

Json必需的包（重新导入包后需重启下，因为这个问题浪费了我好长时间 ，需注意）
commons-beanutils.jar 
commons-lang-2.4.jar
commons-logging-1.1.1.jar
json-lib-2.2.3-jdk13.jar
ezmorph-1.0.6.jar
commons-collections-3.2.1.jar

<script language="javascript">

 function showJSON() {
     var user =
     {
         "username":"andy",
         "age":20,
         "info": { "tel": "123456", "cellphone": "98765"},
         "address":
             [
                 {"city":"beijing","postcode":"222333"},
                 {"city":"newyork","postcode":"555666"}
             ]
     }
     alert(user.username);
     alert(user.age);
     alert(user.info.cellphone);
//或       user.info["cellphone"]
     alert(user.address[0].city);
     alert(user.address[0].postcode);
 }
</script>

 这表示一个user对象，拥有username, age, info, address 等属性。
同样也可以用JSON来简单的修改数据，修改上面的例子
js 代码

function showJSON() {
    var user =
    {
        "username":"andy",
        "age":20,
        "info": { "tel": "123456", "cellphone": "98765"},
        "address":
            [
                {"city":"beijing","postcode":"222333"},
                {"city":"newyork","postcode":"555666"}
            ]
    }
    user.username = "Tom";
    alert(user.username);
}

易错地方 (注意有无外引号)：

    function testJson(){

         var str = { "name": "Violet", "password": "character" };   //JSON类型对象
//无引号，是JSON对象
         alert(typeof(str));  //JSON类型
         alert(str.password);

         //alert(obj.toJSONString());

          var a=50,b="xxx";
          var arr="{id:"+a+",name:'"+b+"'}"; //string类型
              //字符串拼接为可转换为JSON的String

          var str2 = '{ "name": "Violet", "password": "character" }';
//有引号，是String类型对象
          alert(typeof(str2)); //string类型
          var obj = eval('(' + str2 + ')');  //转换为JSON类型
          alert(typeof(obj)); //JSON类型
          alert(obj.name);  //Violet
    }
    </script>

 

JSONObject resultJSON = new JSONObject();
resultJSON.put("param1", 1);
resultJSON.put("param2", 2);
resultJSON.put("param3", 3);
System.out.println(resultJSON);
//{"param1":1,"param2":2,"param3":3}

 

二、Java代码转换成json代码

1.List集合转换成json代码+
List list = new ArrayList();
list.add( "first" );
list.add( "second" );
JSONArray jsonArray2 = JSONArray.fromObject( list );

2.Map集合转换成json代码
Map map = new HashMap();
map.put("name", "json");
map.put("bool", Boolean.TRUE);
map.put("int", new Integer(1));
map.put("arr", new String[] { "a", "b" });
map.put("func", "function(i){ return this.arr[i]; }");
JSONObject json = JSONObject.fromObject(map);
//{"func":function(i){ return this.arr[i]; },"arr":["a","b"],"int":1,"name":"json","bool":true}  

3.Bean转换成json代码
JSONObject jsonObject = JSONObject.fromObject(new JsonBean());

 

//当是对象的时候 
Student student = new Student(); 
student.setAge(18); 
student.setName("zhangsan"); 
student.setSex("male"); 
JSONObject jsonObject = JSONObject.fromObject(student); 
System.out.println(jsonObject);//输出{"age":18,"name":"zhangsan","sex":"male"}

4.数组转换成json代码
boolean[] boolArray = new boolean[] { true, false, true };
JSONArray jsonArray1 = JSONArray.fromObject(boolArray);

5.beans转换成json代码
  List  userInfosList = new ArrayList<UserInfo>();
   UserInfo u1 = new UserInfo();
   u1.setUserId(10000); 
   u1.setUserName("qqqqq");
   u1.setPassword("111111");
   UserInfo u2 = new UserInfo();
   u2.setUserId(10001); 
   u2.setUserName("wwwww"); 
   u2.setPassword("222222");
   userInfosList.add(u1);
   userInfosList.add(u2);
   JSONArray json2=JSONArray.fromObject(userInfosList);

 

     Iterator it=json2.listIterator();
        while(it.hasNext())           
        {

            JSONObject obj=(JSONObject)it.next();
            UserInfo u=(UserInfo)JSONObject.toBean(obj,UserInfo.class); 
            System.out.println(u.getPassword());
        }

6、String转JSON

String listStr = "['apple','orange']";
        //JSONArray json = JSONArray.fromObject(listStr);
                //结果：["apple","orange"]
        //必须用JSONArray来转，用JSONObject会出现以下错误信息：
            // A JSONObject text must begin with '{' at character 1 of ['apple','orange']

        String mapStr2 = "{'apple','orange'}";
        JSONObject json = JSONObject.fromObject(mapStr2);
        //用JSONObject必须是键值对，上面会出现以下错误：
            //Expected a ':' after a key at character 9 of {'apple','orange'}

        String mapStr1 = "{'age':30,'name':'Michael','baby':['Lucy','Lily']}";
        JSONObject json2 = JSONObject.fromObject(mapStr1);
                //{"age":30,"name":"Michael","baby":["Lucy","Lily"]}

        System.out.println(json);

 

三、JSON转List、Map

 

转List：   JSONArray.toCollection(json)

//JSON转List
        String str = "['apple','orange']";
        JSONArray json = JSONArray.fromObject(str);
        Collection<String> list = JSONArray.toCollection(json);
        for (String s : list) {
               System.out.println(s);
        }

 

转Map：JSONObject.toBean(json , Map.class)

//JOSN转Map
        String mapStr = "{'age':30,'name':'Michael','baby':['Lucy','Lily']}";
        JSONObject json3 = JSONObject.fromObject(mapStr);
        Map<String, Object> map = (Map) JSONObject.toBean(json3, Map.class);
        for (Map.Entry<String, Object> entry : map.entrySet()) {
            System.out.println(entry.getKey() + " " + entry.getValue());
        }
        //name Michael
        //age 30
        //baby [Lucy, Lily]

 注意其Str转JSON问题！

 

四、遍历JSON数据的两种常用方式

var json={"status":1,"info":"u83b7u53d6u6210u529f","data":[{"id":"4","name":"u77f3u5bb6u5e84","information":"u5e02","Region_id":"3","type":"1"}]}
var data=json.data;
for(i=0;i<data.length;i++)
{
    document.write("Name:"+data[i].name+",Info:"+data[i].information+"");
}

 

var json=[{"kl_id":"2","kl_title":"Test date1","kl_content":"Test date2","kl_type":"3","id":"6"},{"kl_id":"2","kl_title":"Test1","kl_content":"Test2","kl_type":"1","id":"9"}]
    var str = "";
    for (var one in json)
     {
        for(var key in json[one])
         {
             str += json[one][key] + ",";
         }
     }
     document.write(str);

 

 

。。