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网页中使用传统方法实现异步校验具体解释

        学习JavaScript异步校验时往往是从最传统的XMLHttpRequest学起,今天星期六。我来谈一下对传统校验的认识:

        代码1——index.jsp文件:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%
	String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
	<head>
		<title>怎样使用传统方法异步验证username的唯一性</title>
		<script type="text/javascript">
			function goDemo(pageName){
		        window.location.href=http://www.mamicode.com/''+pageName;>

        代码2——demo1.jsp文件:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%
	String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  	<head>
    	<title>使用的servlet中的doGet方法</title>
		<script type="text/javascript">
	        function checkUserName(){
	  		    var value=http://www.mamicode.com/document.getElementById("userName").value;>

"); var responseValue=http://www.mamicode.com/xmlHttpRequest.responseText;>

</font>"; } }else{//与Servlet交互出现故障 document.getElementById("showUserName").innerHTML="<font size=\"2\" color=\"red\">请求发送失败。</font>"; } } }; if(xmlHttpRequest.readyState==0){ xmlHttpRequest.open("get","<%=basePath%>AjaxCheckUserNameServlet?userName="+value,true);//第二步:完毕请求初始化。提出请求。

open方法中的三个參数各自是:请求方式、路径、是否异步(true表示异步。false表示同步) } } } </script> </head> <body> <center style="margin-top: 10%"><font style="color: red;font-size: 18pt;font-weight: bold;">使用的servlet中的doGet方法</font><br><br> username:<input type="text" id="userName" name="userName" size="27" onblur="checkUserName();"> <font size="2" id="showUserName">  *username必填,具有唯一性。

</font> </center> </body> </html>

        代码3——demo2.jsp文件:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%
	String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+request.getContextPath()+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
	<head>
    	<title>使用的servlet中的doPost方法</title>
		<script type="text/javascript">
			function checkUserName(){
	  		    var value=http://www.mamicode.com/document.getElementById("userName").value;>

"); } if(xmlHttpRequest.readyState==4){//client接收server端信息完毕。第四步:处理server端发回来的响应信息 if(xmlHttpRequest.status==200){//与Servlet成功交互 console.log("client已全然接收server端的处理响应。

"); var responseValue=http://www.mamicode.com/xmlHttpRequest.responseText;>

。</font>"; } }else{//与Servlet交互出现故障 document.getElementById("showUserName").innerHTML="<font size=\"2\" color=\"red\">请求发送失败!

</font>"; } } }; if(xmlHttpRequest.readyState==0){ xmlHttpRequest.open("post","<%=basePath%>AjaxCheckUserNameServlet?userName="+value,true);//第二步:完毕请求初始化,提出请求。

open方法中的三个參数各自是:请求方式、路径、是否异步(true表示异步,false表示同步) } } } </script> </head> <body> <center style="margin-top: 10%"><font color="red" size="5"><strong>使用的servlet中的doPost方法</strong></font><br><br> username:<input type="text" id="userName" name="userName" size="27" onblur="checkUserName()"> <font size=2 id="showUserName">  *username必填,具有唯一性。

</font> </center> </body> </html>

        代码4——AjaxCheckUserNameServlet.java文件:

package com.ghj.packagofserlet;

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;

public class AjaxCheckUserNameServlet extends HttpServlet {

	private static final long serialVersionUID = 6387744976765210524L;

	/**
	 * 处理demo1.jsp中异步验证
	 * 
	 * @author GaoHuanjie
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
		try{
			response.setCharacterEncoding("UTF-8");
			request.setCharacterEncoding("UTF-8");
			PrintWriter out = response.getWriter();
			//System.out.println(1/0);//有益出现异常。以检查demo1.jsp中xmlHttpRequest.status!=200的分支语句是否可用
			String userName=request.getParameter("userName");//获取“username”
			System.out.println("处理demo1.jsp中异步验证,username为:"+userName);
			if ("admin".equals(userName)) {
				out.print("1");//“1”表示username不可用。

} else { out.print("2");//“2”表示username可用。 } out.flush(); out.close(); }catch (Exception e) { e.printStackTrace(); response.setStatus(405); } } /** * 处理demo2.jsp中异步验证 * * @author GaoHuanjie */ public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { try{ response.setCharacterEncoding("UTF-8"); request.setCharacterEncoding("UTF-8"); PrintWriter out = response.getWriter(); //System.out.println(1/0);//有益出现异常,以检查demo2.jsp中xmlHttpRequest.status!=200的分支语句是否可用 String userName=request.getParameter("userName");//获取“username” System.out.println("处理demo2.jsp中异步验证,username为:"+userName); if ("admin".equals(userName)) { out.print("1");//“1”表示username不可用。 } else { out.print("2");//“2”表示username可用。 } out.flush(); out.close(); }catch (Exception e) { e.printStackTrace(); response.setStatus(405); } } }

        代码5——web.xml文件:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

	<servlet>
    	<servlet-name>AjaxCheckUserNameServlet</servlet-name>
    	<servlet-class>com.ghj.packagofserlet.AjaxCheckUserNameServlet</servlet-class>
	</servlet>

	<servlet-mapping>
    	<servlet-name>AjaxCheckUserNameServlet</servlet-name>
    	<url-pattern>/AjaxCheckUserNameServlet</url-pattern>
	</servlet-mapping>
  
	<welcome-file-list>
    	<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
</web-app>
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网页中使用传统方法实现异步校验具体解释