本文实例讲述了AJAX+Servlet实现的数据处理显示功能。，具体如下：
实现功能：在输入框中输入字符，用AJAX传到后台Servlet处理后加上随机数，并返回到前台显示。
一、写前台jsp页面index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP 'index.jsp' starting page</title> <script type="text/javascript"> /* ajax 的几个步骤： 1、建立XmlHttpRequest对象 2、设置回调函数 3、使用Open方法建立与服务器的连接 4、向服务器发送数据 5、在回调函数中针对不同响应状态进行处理 */ var xmlHttp; function createXMLHttpRequest(){ //1建立XmlHttpRequest对象 if(window.ActiveXObject){ try{ xmlHttp = new ActiveXObject("Microsoft.XMLHttp"); }catch(e){ alert("Error!!!"); } }else{ xmlHttp = new XMLHttpRequest(); } } function showMes(){ //2设置回调函数 if(xmlHttp.readyState==4){ //数据接收完成并可以使用 if(xmlHttp.status==200){ //http状态OK //5、在回调函数中针对不同响应状态进行处理 document.getElementById("sp").innerHTML = xmlHttp.responseText; //服务器的响应内容 }else{ alert("出错："+xmlHttp.statusText); //HTTP状态码对应的文本 } } } /** //这是GET方法传送 function getMes(){ createXMLHttpRequest(); var txt = document.getElementById("txt").value; var url="servlet/AjaxServlet?txt="+txt; url = encodeURI(url); //转换码后再传输 xmlHttp.open("GET",url,true); //3使用Open方法建立与服务器的连接 xmlHttp.onreadystatechange=showMes; xmlHttp.send(null); //4向服务器发送数据 } */ /** *这是post方法 */ function postMes(){ createXMLHttpRequest(); var txt = document.getElementById("txt").value; var url = "servlet/AjaxServlet"; var params = "username="+txt; // alert(params); xmlHttp.open("POST",url,true); xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8"); xmlHttp.send(params); xmlHttp.onreadystatechange = showMes; } </script> </head> <body> <input type="text" id="txt"/> <input type="button" value="query" onclick="postMes()" /> <span id="sp"></span> </body></html>二、写后台Servlet加random随机数，关键代码如下：
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); //用utf-8转换获得传输过来的码 response.setContentType("text/html"); PrintWriter out = response.getWriter(); String txt = request.getParameter("txt");// String tx = new String(txt.getBytes("iso-8859"),"utf-8"); out.print("txt="+txt+Math.random()); out.flush(); out.close();}/*** The doPost method of the servlet. <br>** This method is called when a form has its tag value method equals to post.** @param request the request send by the client to the server* @param response the response send by the server to the client* @throws ServletException if an error occurred* @throws IOException if an error occurred*/public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String username = request.getParameter("username");// String txt = new String(username.getBytes("ISO-8859-1"),"UTF-8"); String txt = new String(username); out.print("txt="+txt+":"+Math.random()); out.flush(); out.close();}
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