json对象操作

1.访问json数据

var persons = {

"programmers":[

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

],

"authors":[

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

],

"musicians":[

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

{"firstname":"yang","lastname":"rui","email","[e-mail]"},

],

}

访问：persons .programmers[0].firstname

修改：persons .programmers[0].firstname="jia"

转化：任何javascript对象都可以转换成json字符串 toJSONString()

2.Ajax

json可以轻松地将数据转换为可以在请求中发送给服务器端程序的格式(Ajax)。

1、通过Json格式来声明对象和操作对象 

function showJSON()

{   

    var user =    

    {    

        "username":"andy",

        "age":20,

        "info": { "tel": "123456", "cellphone": "98765"},

        "addresses":   

            [   

                {"city":"beijing","postcode":"222333"},

                {"city":"newyork","postcode":"555666"}

            ]   

    }

    alert(user.username);

    alert(user.age);

    alert(user.info.cellphone);

    alert(user.address[0].city);

    alert(user.address[0].postcode);

}   

这表示一个user对象，拥有username, age, info, address 等属性。

2、一般对象转换成JSON格式的字符

JSON提供了json.js包，下载http://www.json.org/json.js 后，将其引入然后就可以简单的使用object.toJSONString()转换成JSON数据。

js 代码

function Car(make, model, year, color) {   

     this.make  =  make;   

     this.model  =  model;   

     this.year  =  year;   

     this.color  =  color;   

}   

function showCar() {   

    var carr = new Car("Dodge", "Coronet R/T", 1968, "yellow");   

    alert(carr.toJSONString());   

}   

 

js对象和JSON格式的js对象、JSON格式的js对象和JSON文本的转换

可以使用eval来转换JSON字符到JSON格式的Object

js 代码

function myEval() {   

    var str = '{ "name": "张三", "sex": "男" }';   

    var obj = eval('(' + str + ')');   

    alert(obj.toJSONString());   

}   

或者使用parseJSON()方法

function myparse()

{   

    var str= '{ "name": "张三", "sex": "男" }';   

    var obj=str.parseJSON();   //把其Json文本解析成为json对象   

    alert(obj.toJSONString()); //把json对象转换成JSON 文本  

}   

3、从Java 类产生json对象(json-lib)

(1)、JSONObject

          //java对象或满足一定格式的字符串("{username:'admin',password:'12345',..}")转化为JSONObject对象,用法：

JSONObject json=JSONObject.fromObject(userinfo);

//从json对象中根据键名取对应的值, username为键名

json.getObject("username");

//json对象到java对象的转化(jsonobject-->po)

Userinfo userinfo=(Dept)JSONObject.toBean(jsonObject,Userinfo.class);

//Json对象转化成json文本字符串

String josStr=JSONObject.fromObject(userinfo).toString();

(2)、JSONArray

boolean[] boolArray={true,false};

   List list = new ArrayList();  

        Map map=new HashMap();

        object[] test={new Userinfo(),new Userinfo()};

 

       //转化为java的数组Array为json对象

       JSONArray jsonArray = JSONArray.fromObject(boolArray);  

      //System.out.println(jsonArray.toString());

      JSONArray jsonArray1=JSONArray.fromObject("['1','2','3']");

       //System.out.println(jsonArray1.toString());

   

        list.add("first");  

   list.add("second");  

    list.add(new Userinfo());

    //转换java的List为json对象

    JSONArray jsonList = JSONArray.fromObject(list);  

    System.out.println(jsonList);  

    //转换java的Map为json对象

    map.put("name", "windfree");

    map.put("bool", Boolean.TRUE);

    map.put("int",new Integer(0));

    map.put( "arr", new String[]{"a","b"} );

    map.put("func", "function (i){ return this.arr[i]; }");

    map.put("bean",test);

    JSONObject jsonMap = JSONObject.fromObject(map);  

    //System.out.println(jsonMap);