JSON學習[整理]

JSON （ JavaScript Object Notation ）一種簡單的數據格式，比 xml 更輕巧。 JSON 是 JavaScript 原生格式，這意味着在 JavaScript 中處理 JSON 數據不需要任何特殊的 API 或工具包。

JSON 的規則很簡單： 對象是一個無序的“‘名稱 / 值’對”集合。一個對象以“ { ”（左括號）開始，“ } ”（右括號）結束。每個“名稱”後跟一個“ : ”（冒號）；“‘名稱 / 值’ 對”之間使用“ , ”（逗號）分隔。 具體細節參考http://www.json.org/json-zh.html

舉個簡單的例子：

 
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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);     
    alert(user.address[0].city);     
    alert(user.address[0].postcode);     
}     
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);  
    alert(user.address[0].city);  
    alert(user.address[0].postcode);  
}    
這表示一個user對象，擁有username, age, info, address 等屬性。
同樣也可以用JSON來簡單的修改數據，修改上面的例子
js 代碼
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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);     
    alert(user.address[0].city);     
    alert(user.address[0].postcode);     
         
    user.username = "Tom";     
    alert(user.username);     
}  
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);  
    alert(user.address[0].city);  
    alert(user.address[0].postcode);  
      
    user.username = "Tom";  
    alert(user.username);  
} 
 JSON提供了json.js包，下載http://www.json.org/json.js 後，將其引入然後就可以簡單的使用object.toJSONString()轉換成
JSON數據。
js 代碼
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function showCar() {     
    var carr = new Car("Dodge", "Coronet R/T", 1968, "yellow");     
    alert(carr.toJSONString());     
}     
    
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());  
}  
 
function Car(make, model, year, color)       {  
     this.make  =  make;  
     this.model  =  model;  
     this.year  =  year;  
     this.color  =  color;  
}   
可以使用eval來轉換JSON字符到Object
js 代碼
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function myEval() {     
    var str = '{ "name": "Violet", "occupation": "character" }';     
    var obj = eval('(' + str + ')');     
    alert(obj.toJSONString());     
}  
function myEval() {  
    var str = '{ "name": "Violet", "occupation": "character" }';  
    var obj = eval('(' + str + ')');  
    alert(obj.toJSONString());  
} 
或者使用parseJSON()方法
js 代碼
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function myEval() {     
    var str = '{ "name": "Violet", "occupation": "character" }';     
    var obj = str.parseJSON();     
    alert(obj.toJSONString());     
}  
function myEval() {  
    var str = '{ "name": "Violet", "occupation": "character" }';  
    var obj = str.parseJSON();  
    alert(obj.toJSONString());  
} 
下面使用prototype寫一個JSON的ajax例子。
先寫一個servlet (我的是servlet.ajax.JSONTest1.java)就寫一句話
java 代碼
response.getWriter().print("{ /"name/": /"Violet/", /"occupation/": /"character/" }");  
再在頁面中寫一個ajax的請求
js 代碼
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function sendRequest() {     
    var url = "/MyWebApp/JSONTest1";     
    var mailAjax = new Ajax.Request(     
        url,     
        {     
            method: 'get',     
            onComplete: jsonResponse     
        }     
    );     
}     
    
function jsonResponse(originalRequest) {     
    alert(originalRequest.responseText);     
    var myobj = originalRequest.responseText.parseJSON();     
    alert(myobj.name);     
}  
function sendRequest() {  
    var url = "/MyWebApp/JSONTest1";  
    var mailAjax = new Ajax.Request(  
        url,  
        {  
            method: 'get',  
            onComplete: jsonResponse  
        }  
    );  
}  
 
function jsonResponse(originalRequest) {  
    alert(originalRequest.responseText);  
    var myobj = originalRequest.responseText.parseJSON();  
    alert(myobj.name);  
} 
prototype-<st1:chsdate w:st="on" isrocdate="False" islunardate="False" day="30" month="12"
year="1899">1.5.1</st1:chsdate>.js中提供了JSON的方法，String.evalJSON(), 可以不使用json.js, 修改上面的方法
js 代碼
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function jsonResponse(originalRequest) {     
    alert(originalRequest.responseText);     
    var myobj = originalRequest.responseText.evalJSON(true);     
    alert(myobj.name);     
}  
function jsonResponse(originalRequest) {  
    alert(originalRequest.responseText);  
    var myobj = originalRequest.responseText.evalJSON(true);  
    alert(myobj.name);  
} 
JSON還提供了java的jar包 http://www.json.org/java/index.html API也很簡單，下面舉個例子
在javascript中填加請求參數
js 代碼
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function sendRequest() {     
    var carr = new Car("Dodge", "Coronet R/T", 1968, "yellow");     
    var pars = "car=" + carr.toJSONString();     
    
    var url = "/MyWebApp/JSONTest1";     
    var mailAjax = new Ajax.Request(     
        url,     
        {     
            method: 'get',     
            parameters: pars,     
            onComplete: jsonResponse     
        }     
    );     
}  
function sendRequest() {  
    var carr = new Car("Dodge", "Coronet R/T", 1968, "yellow");  
    var pars = "car=" + carr.toJSONString();  
 
    var url = "/MyWebApp/JSONTest1";  
    var mailAjax = new Ajax.Request(  
        url,  
        {  
            method: 'get',  
            parameters: pars,  
            onComplete: jsonResponse  
        }  
    );  
} 
使用JSON請求字符串就可以簡單的生成JSONObject並進行解析,修改servlet添加JSON的處理(要使用json.jar)
java 代碼
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private void doService(HttpServletRequest request, HttpServletResponse response) throws IOException {     
        String s3 = request.getParameter("car");     
        try {     
            JSONObject jsonObj = new JSONObject(s3);     
            System.out.println(jsonObj.getString("model"));     
            System.out.println(jsonObj.getInt("year"));     
        } catch (JSONException e) {     
            e.printStackTrace();     
        }     
        response.getWriter().print("{ /"name/": /"Violet/", /"occupation/": /"character/" }");     
    }  
private void doService(HttpServletRequest request, HttpServletResponse response) throws IOException {  
        String s3 = request.getParameter("car");  
        try {  
            JSONObject jsonObj = new JSONObject(s3);  
            System.out.println(jsonObj.getString("model"));  
            System.out.println(jsonObj.getInt("year"));  
        } catch (JSONException e) {  
            e.printStackTrace();  
        }  
        response.getWriter().print("{ /"name/": /"Violet/", /"occupation/": /"character/" }");  
    } 
同樣可以使用JSONObject生成JSON字符串，修改servlet
java 代碼
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private void doService(HttpServletRequest request, HttpServletResponse response) throws IOException {     
        String s3 = request.getParameter("car");     
        try {     
            JSONObject jsonObj = new JSONObject(s3);     
            System.out.println(jsonObj.getString("model"));     
            System.out.println(jsonObj.getInt("year"));     
        } catch (JSONException e) {     
            e.printStackTrace();     
        }     
             
        JSONObject resultJSON = new JSONObject();     
        try {     
            resultJSON.append("name", "Violet")     
                      .append("occupation", "developer")     
                      .append("age", new Integer(22));     
            System.out.println(resultJSON.toString());     
        } catch (JSONException e) {     
            e.printStackTrace();     
        }     
        response.getWriter().print(resultJSON.toString());     
    }  
private void doService(HttpServletRequest request, HttpServletResponse response) throws IOException {  
        String s3 = request.getParameter("car");  
        try {  
            JSONObject jsonObj = new JSONObject(s3);  
            System.out.println(jsonObj.getString("model"));  
            System.out.println(jsonObj.getInt("year"));  
        } catch (JSONException e) {  
            e.printStackTrace();  
        }  
          
        JSONObject resultJSON = new JSONObject();  
        try {  
            resultJSON.append("name", "Violet")  
                      .append("occupation", "developer")  
                      .append("age", new Integer(22));  
            System.out.println(resultJSON.toString());  
        } catch (JSONException e) {  
            e.printStackTrace();  
        }  
        response.getWriter().print(resultJSON.toString());  
    } 
js 代碼
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function jsonResponse(originalRequest) {     
    alert(originalRequest.responseText);     
    var myobj = originalRequest.responseText.evalJSON(true);     
    alert(myobj.name);     
    alert(myobj.age);     
} 
function jsonResponse(originalRequest) {  
    alert(originalRequest.responseText);  
    var myobj = originalRequest.responseText.evalJSON(true);  
    alert(myobj.name);  
    alert(myobj.age);  
}