08_register.jsp
<%@ page language="java" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>基于HTML，以GET或POST方式，检查注册用户名是否在数据库中已存在</title> </head> <body> <form> 用户名[GET]：<input id="usernameID" type="text" name="username" maxlength="4"/> 光标移出后，立即检查结果 </form> <hr/> <span id="resID"></span> <script type="text/javascript"> //创建AJAX异步对象，即XMLHttpRequest function createAJAX(){ var ajax = null; try{ ajax = new ActiveXObject("microsoft.xmlhttp"); }catch(e1){ try{ ajax = new XMLHttpRequest(); }catch(e2){ alert("你的浏览器不支持ajax，请更换浏览器"); } } return ajax; } </script> <script type="text/javascript"> //定位文本框，同时提供焦点失去事件 document.getElementById("usernameID").onblur = function(){ //获取文本框中输入的值 var username = this.value; //如果用户没有填内容 if(username.length == 0){ //提示 document.getElementById("resID").innerHTML = "用户名必填"; }else{ //对汉字进行UTF-8(U8)的编码 username = encodeURI(username); //NO1) var ajax = createAJAX(); //NO2) var method = "GET"; var url = "${pageContext.request.contextPath}/UserServlet?time="+new Date().getTime()+"&username=" + username; ajax.open(method,url); //NO3) ajax.send(null); //--------------------------------------------------------等待 //NO4) ajax.onreadystatechange = function(){ if(ajax.readyState == 4){ if(ajax.status == 200){ //NO5) var tip = ajax.responseText; //NO6) document.getElementById("resID").innerHTML = tip; } } } } } </script> </body> </html>
09_register.jsp
<%@ page language="java" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>基于HTML，以GET或POST方式，检查注册用户名是否在数据库中已存在</title> <!-- 引入外部js文本 --> <script type="text/javascript" src="js/ajax.js"></script> </head> <body> 用户名[POST]：<input id="usernameID" type="text" maxlength="4"/> <span id="resID"> <!-- <img src="tip变量" width="12px" height="12px"/> --> </span> <hr/> <script type="text/javascript"> document.getElementById("usernameID").onblur = function(){ var username = this.value;//杰克 //NO1) var ajax = createAJAX(); //NO2) var method = "POST"; var url = "${pageContext.request.contextPath}/UserServlet?time="+new Date().getTime(); ajax.open(method,url); //设置AJAX请求头为POST，他会将请求体中的汉字自动进行UTF-8的编码 ajax.setRequestHeader("content-type","application/x-www-form-urlencoded"); //NO3) var content = "username=" + username; ajax.send(content); //===========================================等待 //NO4) ajax.onreadystatechange = function(){ if(ajax.readyState == 4){ if(ajax.status == 200){ //NO5) var tip = ajax.responseText; //NO6) //创建img标签 var imgElement = document.createElement("img"); //设置img标签的src/width/height的属性值 imgElement.src = tip; imgElement.style.width = "12px"; imgElement.style.height = "12px"; //定位span标签 var spanElement = document.getElementById("resID"); //清空span标签中的内容 spanElement.innerHTML = ""; //将img标签加入到span标签中 spanElement.appendChild(imgElement); } } } } </script> <!-- <form action="" method="" enctype="application/x-www-form-urlencoded"></form> --> </body> </html>
package loaderman.user; 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; /** * 基于HTML，以GET或POST方式，检查注册用户名是否在数据库中已存在 */ public class UserServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { String username = request.getParameter("username"); byte[] buf = username.getBytes("ISO8859-1"); username = new String(buf,"UTF-8"); System.out.println("username=" + username); String tip = "<font color='green'>可以注册</font>"; if("杰克".equals(username)){ tip = "<font color='red'>该用户已存在</font>"; } response.setContentType("text/html;charset=UTF-8"); PrintWriter pw = response.getWriter(); pw.write(tip); pw.flush(); pw.close(); } public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); String username = request.getParameter("username"); System.out.println("username=" + username); String tip = "images/MsgSent.gif"; if("杰克".equals(username)){ tip = "images/MsgError.gif"; } response.setContentType("text/html;charset=UTF-8"); PrintWriter pw = response.getWriter(); pw.write(tip); pw.flush(); pw.close(); } }