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Detailed explanation of traditional JavaScript methods to implement asynchronous verification_javascript skills
Detailed explanation of traditional JavaScript methods to implement asynchronous verification_javascript skills
When learning JavaScript asynchronous verification, you often start with the most traditional XMLHttpRequest. This article will talk about the understanding of traditional verification:
Code 1index.jsp file:
<%@ 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>如何使用传统方法异步验证用户名的唯一性</title>
<script type="text/javascript">
function goDemo(pageName){
window.location.href='<%=basePath%>'+pageName;
}
</script>
</head>
<body>
<center style="margin-top: 10%"><font style="color: red;font-size: 18pt;font-weight: bold;">如何使用传统方法异步验证用户名的唯一性</font></center><br>
例子一：<input type="button" value="例子一" onclick="goDemo('demo1.jsp');"/><br><br>
例子二：<input type="button" value="例子二" onclick="goDemo('demo2.jsp');"/><br><br>
例子一与例子二的区别：两者都实现了使用传统方法异步验证用户名的唯一性的功能，区别在于使用的servlet中的的方法不同："例子一"使用的servlet中的doGet方法；"例子二"使用的servlet中的doPost方法。
</body>
</html>
Code 2demo1.jsp file:
<%@ 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=document.getElementById("userName").value;
if(value==""){
document.getElementById("showUserName").innerHTML="<font size=\"2\" color=red>用户名不能为空！！！</font>";
}else{
var xmlHttpRequest = null;
if(window.XMLHttpRequest){/*适用于IE7以上（包括IE7）的IE浏览器、火狐浏览器、谷歌浏览器和Opera浏览器*/
xmlHttpRequest = new XMLHttpRequest();//创建XMLHttpRequest
}else if(window.ActiveXObject){/*适用于IE6.0以下（包括IE6.0）的IE浏览器*/
xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
}//第一步：创建XMLHttpRequest对象，请求未初始化
xmlHttpRequest.onreadystatechange = function (){//readyState值发生改变时XMLHttpRequest对象激发一个readystatechange事件,进而调用后面的函数
if(xmlHttpRequest.readyState==1){
xmlHttpRequest.send();//第三步：发送请求，也可以为xmlHttpRequest.send(null)
}
if(xmlHttpRequest.readyState==2){
console.log("send()方法已执行，请求已发送到服务器端，但是客户端还没有收到服务器端的响应。");
}
if(xmlHttpRequest.readyState==3){
console.log("已经接收到HTTP响应头部信息，但是消息体部分还没有完全接收结束。");
}
if(xmlHttpRequest.readyState==4){//客户端接收服务器端信息完毕。第四步：处理服务器端发回来的响应信息
if(xmlHttpRequest.status==200){//与Servlet成功交互
console.log("客户端已完全接收服务器端的处理响应。");
var responseValue=xmlHttpRequest.responseText;
if(responseValue==1){
document.getElementById("showUserName").innerHTML="<font size=\"2\" color=\"red\"> 用户名已被使用！</font>";
}else if(responseValue==2){
document.getElementById("showUserName").innerHTML="<font size=\"2\" color=\"green\"> 用户名有效！！！</font>";
}
}else{//与Servlet交互出现问题
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：完成请求初始化，提出请求。open方法中的三个参数分别是：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>
用户名：<input type="text" id="userName" name="userName" size="27" onblur="checkUserName();">
<font size="2" id="showUserName"> *用户名必填，具有唯一性。</font>
</center>
</body>
</html>
Code 3demo2.jsp file:
<%@ 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=document.getElementById("userName").value;
if(value==""){
document.getElementById("showUserName").innerHTML="<font size=\"2\" color=red>用户名不能为空！！！</font>";
}else{
var xmlHttpRequest = null;
if(window.XMLHttpRequest){/*适用于IE7以上（包括IE7）的IE浏览器、火狐浏览器、谷歌浏览器和Opera浏览器*/
xmlHttpRequest = new XMLHttpRequest();//创建XMLHttpRequest
}else if(window.ActiveXObject){/*适用于IE6.0以下（包括IE6.0）的IE浏览器*/
xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
}//第一步：创建XMLHttpRequest对象，请求未初始化
xmlHttpRequest.onreadystatechange = function (){//readyState值发生改变时XMLHttpRequest对象激发一个readystatechange事件,进而调用后面的函数
if(xmlHttpRequest.readyState==1){
xmlHttpRequest.send();//第三步：发送请求，也可以为xmlHttpRequest.send(null)
}
if(xmlHttpRequest.readyState==2){
console.log("send()方法已执行，请求已发送到服务器端，但是客户端还没有收到服务器端的响应。");
}
if(xmlHttpRequest.readyState==3){
console.log("已经接收到HTTP响应头部信息，但是消息体部分还没有完全接收结束。");
}
if(xmlHttpRequest.readyState==4){//客户端接收服务器端信息完毕。第四步：处理服务器端发回来的响应信息
if(xmlHttpRequest.status==200){//与Servlet成功交互
console.log("客户端已完全接收服务器端的处理响应。");
var responseValue=xmlHttpRequest.responseText;
if(responseValue==1){
document.getElementById("showUserName").innerHTML="<font size=\"2\" color=\"red\"> 用户名已被使用！</font>";
}else if(responseValue==2){
document.getElementById("showUserName").innerHTML="<font size=\"2\" color=\"green\"> 用户名有效！！！</font>";
}
}else{//与Servlet交互出现问题
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：完成请求初始化，提出请求。open方法中的三个参数分别是：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>
用户名：<input type="text" id="userName" name="userName" size="27" onblur="checkUserName()">
<font size=2 id="showUserName"> *用户名必填，具有唯一性。</font>
</center>
</body>
</html>
Code 4AjaxCheckUserNameServlet.java file:
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);//故意出现异常，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“用户名”
System.out.println("处理demo1.jsp中异步验证，用户名为："+userName);
if ("admin".equals(userName)) {
out.print("1");//“1”表示用户名不可用。
} else {
out.print("2");//“2”表示用户名可用。
}
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);//故意出现异常，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“用户名”
System.out.println("处理demo2.jsp中异步验证，用户名为："+userName);
if ("admin".equals(userName)) {
out.print("1");//“1”表示用户名不可用。
} else {
out.print("2");//“2”表示用户名可用。
}
out.flush();
out.close();
}catch (Exception e) {
e.printStackTrace();
response.setStatus(405);
}
}
}
Code 5web.xml file:
<?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> The above is the detailed code for implementing asynchronous verification using traditional methods. I hope it will be helpful to everyone's learning.
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