Three Ajax implementation methods and AJAX parsing JSON

This time I will bring you three Ajax implementation methods and AJAX parsing JSON. What are the precautions for Ajax three implementation methods and AJAX parsing JSON? Here are practical cases, let’s take a look.

Preparation:

1、 prototype.js
2、 jquery1.3.2.min.js
3、 json2.js

Background processing program (Servlet), access path servlet/testAjax:

Java code

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例子后台处理程序 
 * @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); 
  } 
}

TestAjaxServlet receives two parameters: name and age, and returns a JSON String written in format.

Front page parameter input interface:

Html code

<p>显示区域</p> 
<p> 
  name:<input><br> 
  age:<input><br> 
</p>

1. Prototype implementation

Html code

<script></script> 
  <script> 
    function prototypeAjax() 
    {     
    var url = "servlet/testAjax";//请求URL 
    var params = Form.serialize("parameters");//提交的表单 
   var myAjax = new Ajax.Request( 
    url,{ 
      method:"post",// 请求方式  
      parameters:params, // 参数 
      onComplete:pressResponse, // 响应函数 
      asynchronous:true 
    }); 
    $("show").innerHTML = "正在处理中..."; 
    } 
    function pressResponse(request) 
    { 
    var obj = request.responseText; // 以文本方式接收 
    $("show").innerHTML = obj; 
    var objJson = request.responseText.evalJSON(); // 将接收的文本用解析成Json格式 
    $("show").innerHTML += "name=" + objJson[&#39;name&#39;] + " age=" + objJson[&#39;age&#39;]; 
    } 
</script> 
<input><br>

In the Ajax implementation of prototype, use the evalJSON method to convert the string into a JSON object.

2. jquery implementation

Html code

<script></script> 
<script></script> 
<input><br> 
<script> 
    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",//请求页面返回的数据类型   
         type: "GET",   
         contentType: "application/json",//注意请求页面的contentType 要于此处保持一致   
         success:function(data) {//这里的data是由请求页面返回的数据  
         var dataJson = JSON.parse(data); // 使用json2.js中的parse方法将data转换成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); // 绑定提交按钮 
 </script>

I’m new to jQuery, and I’m in json The processing is done with the help of json2.js. I also ask my seniors for advice. .

3. XMLHttpRequest implementation

##Html code

<script> 
    var xmlhttp;  
    function XMLHttpRequestAjax()  
    { 
      // 获取数据 
     var name = document.getElementById("name").value;  
       var age = document.getElementById("age").value;  
     // 获取XMLHttpRequest对象 
     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; //回调函数 
       var time = new Date();// 在url后加上时间，使得每次请求不一样 
       var url = "servlet/testAjax?name="+name+"&age="+age+"&time="+time; 
       xmlhttp.open("GET",url,true); // 以get方式发送请求 
       xmlhttp.send(null);  // 参数已在url中，所以此处不需要参送 
    }    
    function callback(){   
      if(xmlhttp.readyState == 4){   
       if(xmlhttp.status == 200){ // 响应成功  
         var responseText = xmlhttp.responseText;  // 以文本方式接收响应信息 
         var userp = document.getElementById("show"); 
         var responseTextJson = JSON.parse(responseText); // 使用json2.js中的parse方法将data转换成json格式  
         userp.innerHTML=responseText + " name=" + responseTextJson.name + " age=" + responseTextJson.age; 
       } 
      }     
    } 
</script> 
<input><br>

ps :Three ways to convert strings into JSON

During project development using Ajax, it is often necessary to return strings in JSON format to the front end, and the front end parses them into JS objects (JSON) .

ECMA-262(E3) did not write the JSON concept into the standard, but in ECMA-262(E5) the concept of JSON was officially introduced, including the global JSON object and the Date toJSON method.

1, eval method analysis, I am afraid this is the earliest analysis method.

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

Remember the parentheses on both sides of str.

2, the new Function form is quite weird.

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

In IE6/7, when the string contains a newline (\n), new Function cannot parse it, but eval can.

3, use the global JSON object.

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

Currently IE8(S)/Firefox3.5/Chrome4/Safari4/Opera10 has implemented this method.

When using JSON.parse, you must strictly abide by the JSON specification. For example, attributes need to be enclosed in quotation marks, as follows

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

name is not enclosed in quotation marks. When using JSON.parse, all browsers will throw Exception, parsing failed. The first two methods are fine.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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