jsp頁面部分：通過JS進行客戶端的表單驗證，主要驗證表單的格式、輸入是否正確，使用這種方式可以避免在提交之後才返回一個簡單的輸入錯誤，在網速較慢的情況下更能提高效率。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@page language="java" contentType="text/html;charset=GBK"%><html><head><script language="javascript" type="text/javascript"><!--var http = getHTTPObject();function handleHttpResponse(){//判斷xmlHttpRequest對象的狀態if(http.readyState == 4){if(http.status == 200){var xmlDocument = http.responseXML;//如果返回值不爲空if(http.responseText!=""){//顯示返回內容document.getElementById("showStr").style.display = "";document.getElementById("userName").style.background= "#FF0000";document.getElementById("showStr").innerText = http.responseText;}else{//如果返回值爲空，不顯示document.getElementById("userName").style.background= "#FFFFFF";document.getElementById("showStr").style.display = "none";}}else{alert("你所請求的頁面發生異常，可能會影響你瀏覽該頁的信息！");alert(http.status);}}}function handleHttpResponse1(){if(http.readyState == 4){if(http.status == 200){var xmlDocument = http.responseXML;if(http.responseText!=""){document.getElementById("comNmStr").style.display = "";document.getElementById("comNm").style.background= "#FF0000";document.getElementById("comNmStr").innerText = http.responseText;}else{document.getElementById("comNm").style.background= "#FFFFFF";document.getElementById("comNmStr").style.display = "none";}}else{alert("你所請求的頁面發生異常，可能會影響你瀏覽該頁的信息！");alert(http.status);}}}//檢測用戶名稱function chkUser(){var url = "/chkUserAndCom";var name = document.getElementById("userName").value;url += ("&userName="+name+"&oprate=chkUser");http.open("GET",url,true);http.onreadystatechange = handleHttpResponse;http.send(null);return ;}//檢測企業名稱function chkComNm(){var url = "/chkUserAndCom";var name = document.getElementById("comNm").value;url += ("&comName="+name+"&oprate=chkCom");http.open("GET",url,true);http.onreadystatechange = handleHttpResponse1;http.send(null);return ;}//該函數可以創建需要的XMLHttpRequest對象function getHTTPObject(){var xmlhttp = false;if(window.XMLHttpRequest){xmlhttp = new XMLHttpRequest();if(xmlhttp.overrideMimeType){xmlhttp.overrideMimeType('text/xml');}}else{try{xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");}catch(e){try{xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");}catch(E){xmlhttp = false;}}}return xmlhttp;}//檢測表單輸入是否合法function chkpassword(){//獲取表單var m=document.form1;//判斷密碼輸入是否合法if(len(m.password.value) > 20 || len(m.password.value) < 5 || !isStr(m.password.value)){document.getElementById("passwordStr").style.display = "";document.getElementById("password").style.background= "#FF0000";document.getElementById("passwordStr").innerText = "對不起,密碼必須爲英文字母、數字或下畫線，長度爲5~20!";}else{document.getElementById("password").style.background= "#FFFFFF";document.getElementById("passwordStr").style.display = "none";}}//判斷第二次輸入是否合法、一致function chkconfirmPassword(){var m=document.form1;if (m.password.value != m.confirmPassword.value){document.getElementById("confirmPasswordStr").style.display = "";document.getElementById("confirmPassword").style.background= "#FF0000";document.getElementById("confirmPasswordStr").innerText = "對不起,密碼與重複密碼不一致!";}else{document.getElementById("confirmPassword").style.background= "#FFFFFF";document.getElementById("confirmPasswordStr").style.display = "none";}}//判斷所有文本框中的輸入function checkfield(){var m=document.form1;if(m.userName.value.length==0){alert("對不起,用戶名必須爲英文字母、數字或下畫線，長度爲5~20。");m.userName.focus();return false;}if(m.password.value.length==0){alert("對不起,密碼必須爲英文字母、數字或下畫線，長度爲5~20。");m.password.focus();return false;}if (m.password.value != m.confirmPassword.value){alert("對不起,密碼與重複密碼不一致!");m.confirmPassword.focus();return false;}if(m.comNm.value.length==0){alert("對不起,企業名稱不能爲空！！");m.comNm.focus();return false;}m.submit();}//--></script></head><body topmargin="0"><form name="form1" method="post" action="/Control?act=Register"><table width="100%"><tr><td align="center"> <H1>Ajax 演示程序</H1></td></tr><tr><td align="center"> ------ 企業註冊 By Alpha</td></tr></table><HR><table width="400" border="0" cellpadding="1" cellspacing="1" align="center" ><tr><td><font color="red">*</font></td><td>用戶帳號:</td><td><input type="text" name="userName" maxlength="20" style="background:#FFFFFF" onBlur="chkUser()" value=""/><div id="showStr" style="background-color:#FF9900;display:none"></div></td></tr><tr><td><font color="red">*</font></td><td>企業名稱:</td><td><input type="text" name="comNm" maxlength="100" style="background:#FFFFFF" onBlur="chkComNm()" value=""/><div id="comNmStr" style="background-color:#FF9900;display:none"></div></td></tr><tr><td><font color="red">*</font></td><td>用戶密碼:</td><td><input type="password" name="password" maxlength="20" style="background:#FFFFFF" onBlur="chkpassword()"/><div id="passwordStr" style="background-color:#FF9900;display:none"></div></td></tr><tr><td><font color="red">*</font></td><td>確認密碼:</td><td><input type="password" name="confirmPassword" maxlength="20" style="background:#FFFFFF" onBlur="chkconfirmPassword()"/><div id="confirmPasswordStr" style="background-color:#FF9900;display:none"></div></td></tr></table><div align="center"><input type="button" name="ok" value=" 確 定 " onclick="checkfield()"> <input type="reset" name="reset" value=" 取 消 "></div></form></body></html>
servlet部分:進行數據庫方面的驗證，主要用於查看在數據庫中有沒有存在該用戶或企業。
package com.event;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.beans.EBaseInfo;public class CheckUserAndComNm {private String msgStr = "";protected void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException{EComBaseInfo info=new EComBaseInfo();//獲取請求中的參數String oprate=request.getParameter("oprate")).trim();String userName=request.getParameter("userName");String passWord=request.getParameter("password");String comName=request.getParameter("comName");try{//判斷是否是檢查用戶名if(oprate.equals("chkUser")){response.setContentType("text/html;charset=GB2312");if(userName.length()＜5||userName.length()＞20){msgStr = "對不起,用戶名必須爲字母、數字或下畫線，長度爲5-20個字符!";}else{boolean bTmp=info.findUser(userName);//查詢數據庫中有無該用戶名if(bTmp)msgStr ="對不起,此用戶名已經存在,請更換用戶名註冊!";elsemsgStr ="";}response.getWriter().write(msgStr);}//檢查企業名else if(oprate.equals("chkCom")){response.setContentType("text/html;charset=GB2312");if(comName.length()＜6||comName.length()＞100){msgStr = "對不起,公司名稱長度爲6-100個字符(不包括字符內的空格)!";}else{boolean bTmp=info.findCom(comName);//查找數據庫中有無該企業名if(bTmp)msgStr ="對不起,此企業名稱已經存在,請更換企業名稱註冊!";elsemsgStr ="";}response.getWriter().write(msgStr);}}catch(Exception ex){}finally{request.setAttribute("url",url);}}protected void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException{doGet(request,response);}}