Ajax三種實現方法與AJAX解析JSON

package ajax.servlet; 
import java.io.IOException; 
import java.io.PrintWriter; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
/** 
 * Ajax例子后臺處理程序 
 * @author bing 
 * @version 2011-07-07 
 * 
 */ 
public class TestAjaxServlet extends HttpServlet { 
 public void doGet(HttpServletRequest request, HttpServletResponse response) 
 throws ServletException, IOException { 
 response.setContentType("text/html;charset=utf-8"); 
 PrintWriter out = response.getWriter(); 
 String name = request.getParameter("name"); 
 String age = request.getParameter("age"); 
 System.out.println("{\"name\":\"" + name + "\",\"age\":\"" + age + "\"}"); 
 out.print("{\"name\":\"" + name + "\",\"age\":" + age + "}"); 
 out.flush(); 
 out.close(); 
 } 
 public void doPost(HttpServletRequest request, HttpServletResponse response) 
 throws ServletException, IOException { 
 doGet(request,response); 
 } 
}

<p id="show">顯示區域</p> 
<p id="parameters"> 
 name:<input id="name" name="name" type="text" /><br /> 
 age:<input id="age" name="age" type="text" /><br /> 
</p>

<script type="text/javascript" src="prototype.js"></script> 
 <script type="text/javascript"> 
 function prototypeAjax() 
 { 
 var url = "servlet/testAjax";//請求URL 
 var params = Form.serialize("parameters");//提交的表單 
 var myAjax = new Ajax.Request( 
 url,{ 
 method:"post",// 請求方式 
 parameters:params, // 參數 
 onComplete:pressResponse, // 響應函數 
 asynchronous:true 
 }); 
 $("show").innerHTML = "正在處理中..."; 
 } 
 function pressResponse(request) 
 { 
 var obj = request.responseText; // 以文本方式接收 
 $("show").innerHTML = obj; 
 var objJson = request.responseText.evalJSON(); // 將接收的文本用解析成Json格式 
 $("show").innerHTML += "name=" + objJson['name'] + " age=" + objJson['age']; 
 } 
</script> 
<input id="submit" type="button" value="提交" onclick="prototypeAjax()" /><br />

<script type="text/javascript" src="jquery-1.3.2.min.js"></script> 
<script type="text/javascript" src="json2.js"></script> 
<input id="submit" type="button" value="提交" /><br /> 
<script type="text/javascript"> 
 function jqueryAjax() 
 { 
 var user={"name":"","age":""}; 
 user.name= $("#name").val(); 
 user.age=$("#age").val(); 
 var time = new Date(); 
 $.ajax({ 
 url: "servlet/testAjax?time="+time, 
 data: "name="+user.name+"&age="+user.age, 
 datatype: "json",//請求頁面返回的數據類型 
 type: "GET", 
 contentType: "application/json",//注意請求頁面的contentType 要于此處保持一致 
 success:function(data) {//這里的data是由請求頁面返回的數據 
 var dataJson = JSON.parse(data); // 使用json2.js中的parse方法將data轉換成json格式 
 $("#show").html("data=" + data + " name="+dataJson.name+" age=" + dataJson.age); 
 }, 
 error: function(XMLHttpRequest, textStatus, errorThrown) { 
 $("#show").html("error"); 
 } 
 }); 
 } 
 $("#submit").bind("click",jqueryAjax); // 綁定提交按鈕 
 </script>

<script type="text/javascript"> 
 var xmlhttp; 
 function XMLHttpRequestAjax() 
 { 
 // 獲取數據 
 var name = document.getElementById("name").value; 
 var age = document.getElementById("age").value; 
 // 獲取XMLHttpRequest對象 
 if(window.XMLHttpRequest){ 
 xmlhttp = new XMLHttpRequest(); 
 }else if(window.ActiveXObject){ 
 var activxName = ["MSXML2.XMLHTTP","Microsoft.XMLHTTP"]; 
 for(var i = 0 ; i < activexName.length; i++){ 
 try{ 
 xmlhttp = new ActiveXObject(activexName[i]); 
 break; 
 }catch(e){} 
 } 
 } 
 xmlhttp.onreadystatechange = callback; //回調函數 
 var time = new Date();// 在url后加上時間，使得每次請求不一樣 
 var url = "servlet/testAjax?name="+name+"&age="+age+"&time="+time; 
 xmlhttp.open("GET",url,true); // 以get方式發送請求 
 xmlhttp.send(null); // 參數已在url中，所以此處不需要參送 
 } 
 function callback(){ 
 if(xmlhttp.readyState == 4){ 
 if(xmlhttp.status == 200){ // 響應成功 
 var responseText = xmlhttp.responseText; // 以文本方式接收響應信息 
 var userp = document.getElementById("show"); 
 var responseTextJson = JSON.parse(responseText); // 使用json2.js中的parse方法將data轉換成json格式 
 userp.innerHTML=responseText + " name=" + responseTextJson.name + " age=" + responseTextJson.age; 
 } 
 } 
 } 
</script> 
<input id="submit" type="button" value="提交" onclick="XMLHttpRequestAjax()" /><br />

function strToJson(str){
 var json = eval('(' + str + ')');
 return json;
}

function strToJson(str){
 var json = (new Function("return " + str))();
 return json;
}

function strToJson(str){
 return JSON.parse(str);
}

var str = '{name:"jack"}';
var obj = JSON.parse(str); // --> parse error