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案例实现效果
用户在前端输入验证码，按键收起触发异步验证，验证验证码的对错
前端代码
checkcode.jsp
<%--
Created by IntelliJ IDEA.
User: cxspace
Date: 16-8-18
Time: 下午7:45
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>验证码检查</title>
<script type="text/javascript" src="js/ajax.js"></script>
</head>
<body>
<form>
<table border="0" align="center">
<th>验证码:</th>
<td><input size="3" type="text" name="checkcode" id="checkcodeID" maxlength="4"/></td>
<td><img src="check/checkImage.jsp" /></td>
<td id="res"></td>
</table>
</form>
<script type="text/javascript">
//去掉两边空格
function trim(str) {
//正则表达式去掉左边空格
str = str.replace(/^\s*/,""); //换掉左边空格
str = str.replace(/\s*$/,""); //换掉右边空格
return str;
}
</script>
<script type="text/javascript">
document.getElementById("checkcodeID").onkeyup = function () {
var checkcode = this.value;
var checkcode = trim(checkcode);
if (checkcode.length == 4){
var ajax = createAJAX();
var method = "POST";
var url = "${pageContext.request.contextPath}/checkRequest?time="+new Date().getTime();
ajax.open(method,url);
ajax.setRequestHeader("content-type","application/x-www-form-urlencoded");
var content = "checkcode="+checkcode;
ajax.send(content);
ajax.onreadystatechange = function () {
if(ajax.readyState == 4){
if (ajax.status == 200){
var tip = ajax.responseText;
var img = document.createElement("img");
img.src = tip;
img.style.width = "14px";
img.style.height = "14px";
var td = document.getElementById("res");
td.innerHTML="";
td.appendChild(img)
}
}
}
}else {
var td = document.getElementById("res");
td.innerHTML = "";
}
}
</script>
</body>
</html>
ajax.jsp
//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;
}
checkImage.jsp
<%--
Created by IntelliJ IDEA.
User: cxspace
Date: 16-8-18
Time: 下午5:39
To change this template use File | Settings | File Templates.
--%>
<%@ page language="java" pageEncoding="UTF-8" %>
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
//获取随机颜色值
public Color getColor(){
Random random = new Random();
int r = random.nextInt(256);
int g = random.nextInt(256);
int b = random.nextInt(256);
Color color = new Color(r,g,b);
return color;
}
//获取四位随机数连成的字符串
public String getNum(){
String str = "";
Random random = new Random();
for(int i = 0 ; i < 4 ; i++){
str += random.nextInt(10);
}
return str;
}
%>
<%
//设置浏览器不缓存图片
response.setHeader("pragma","mo-cache");
response.setHeader("cache-control","no-cache");
response.setDateHeader("expires",0);
//设置图片大小和背景
BufferedImage image = new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB);
//创建画笔对象
Graphics g = image.getGraphics();
g.setColor(new Color(200,200,200));
g.fillRect(0,0,80,30);
for (int i = 0 ; i < 20 ; i++){
Random random = new Random();
int x = random.nextInt(80);
int y = random.nextInt(30);
int x1 = random.nextInt(x+10);
int y1 = random.nextInt(y+10);
//背景模糊线使用随机色
g.setColor(getColor());
g.drawLine(x,y,x+x1,y+y1);
}
g.setFont(new Font("serif",Font.BOLD,16));
g.setColor(Color.black);
String checkNum = getNum();
//给字符串字符之间加空格
StringBuffer sb = new StringBuffer();
for (int i = 0 ; i < checkNum.length() ; i ++){
sb.append(checkNum.charAt(i)+" ");
}
g.drawString(sb.toString(),10,20);
session.setAttribute("checkNum",checkNum);
ImageIO.write(image,"jpeg",response.getOutputStream());
out.clear();
out = pageContext.pushBody();
%>
后端代码
action配置
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
<package name="myPackage" namespace="/" extends="struts-default">
<action name="checkRequest"
class="checkcode.CheckcodeAction"
method="check">
</action>
</package>
</struts>
checkcode.CheckcodeAction
package checkcode;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import org.apache.struts2.ServletActionContext;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;
/**
* Created by cxspace on 16-8-18.
*/
public class CheckcodeAction extends ActionSupport{
private String checkcode;
public void setCheckcode(String checkcode) {
this.checkcode = checkcode;
}
public String check() throws Exception {
String tip = "images/MsgError.gif";
String checkcodeServer = (String) ActionContext.getContext().getSession().get("checkNum");
if (checkcode.equals(checkcodeServer)){
tip="images/MsgSent.gif";
}
HttpServletResponse response = ServletActionContext.getResponse();
response.setContentType("text/html;charset=UTF-8");
PrintWriter pw = response.getWriter();
pw.write(tip);
pw.flush();
pw.close();
return null;
}
}
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原文地址：http://www.cnblogs.com/cxspace/p/5785266.html
