1、前台的代码
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP ‘pic-login.jsp‘ starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script type="text/javascript" src="js/jquery-1.8.3.min.js"></script>
<script type="text/javascript">
function reload(){
document.getElementById("image").src="<%=request.getContextPath() %>/ImageServlet?date="+new Date().getTime();
$("#checkcode").val(""); // 将验证码清空
}
function verificationcode(){
var text=$.trim($("#checkcode").val());
$.post("${pageContext.request.contextPath}/VerificationServlet",{op:text},function(data){
data=parseInt($.trim(data));
if(data>0){
$("#span").text("验证成功!").css("color","green");
}else{
$("#span").text("验证失败!").css("color","red");
reload(); //验证失败后需要更换验证码
$("#checkcode").val(""); // 将验证码清空
}
});
}
</script>
</head>
<body>
验证码：<input type="text" name="checkcode" id="checkcode" onchange="javascript:verificationcode()"/>
<img src="<%=request.getContextPath() %>/ImageServlet" title="点击换一张" id="image" onclick="javascript:reload()"/> <span id="span"></span>
</body>
</html>
2、这里图片的src是一个servlet-ImageServlet.java
package com.java.servlet;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet("/ImageServlet")
public class ImageServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public ImageServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
//在内存中创建图象
int width = 80;
int height = 25;
BufferedImage bfi = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//创建图象
Graphics g = bfi.getGraphics();
g.fillRect(0, 0, width, height);
//验证码字符范围
char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".toCharArray();
Random r = new Random();
int index;
StringBuffer sb = new StringBuffer(); //保存字符串
//随机产生认证码
for(int i=0; i<4; i++){
index = r.nextInt(ch.length);
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
Font font = new Font("Tines Nev Roman", 30, 20);
g.setFont(font);
g.drawString(ch[index]+"", (i*20)+2, 23);
sb.append(ch[index]);
}
// 添加噪点
int area = (int) (0.02 * width * height);
for(int i=0; i<area; ++i){
int x = (int)(Math.random() * width);
int y = (int)(Math.random() * height);
bfi.setRGB(x, y, (int)(Math.random() * 255));
}
//设置验证码中的干扰线
for (int i = 0; i < 1; i++) {
//随机获取干扰线的起点和终点
int xstart = (int)(Math.random() * width);
int ystart = (int)(Math.random() * height);
int xend = (int)(Math.random() * width);
int yend = (int)(Math.random() * height);
g.setColor(interLine(1, 255));
g.drawLine(xstart, ystart, xend, yend);
}
HttpSession session = request.getSession(); //保存到session
session.setAttribute("verificationCode", sb.toString());
ImageIO.write(bfi, "JPG", response.getOutputStream()); //写到输出流
}
private static Color interLine(int Low, int High){
if(Low > 255)
Low = 255;
if(High > 255)
High = 255;
if(Low < 0)
Low = 0;
if(High < 0)
High = 0;
int interval = High - Low;
int r = Low + (int)(Math.random() * interval);
int g = Low + (int)(Math.random() * interval);
int b = Low + (int)(Math.random() * interval);
return new Color(r, g, b);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
这里使用ImageServlet生成图片验证码，使用post后台验证，在点击标签换验证码图片的时候，一定要在调用生成图片前加一个时间戳，也就是上面的document.getElementById("image").src="<%=request.getContextPath() %>/imageServlet?date="+new Date().getTime();这句代码的最后加？后面的代码一定不能少，因为浏览器是由缓存的，如果不加时间戳，在点击标签换图片时，验证码图片不会正常更换。
为了便于比对结果，一定要将字符串保存到session。因为session是当前会话有效的，也就是说在你关闭浏览器之前，session里的值都是可以取到的。这里为了增加验证的难度，是不区分大小写的。噪点和干扰线的数量也是可调的。
3、最后是使用VerificationServlet对验证码图片上的字符与输入的字符串进行比对！把存入session中的verificationCode取出来与checkcode进行比对，返回结果
package com.java.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet("/VerificationServlet")
public class VerificationServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public VerificationServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session =request.getSession();
String verificationCode = (String)session.getAttribute("verificationCode");
String checkcode = request.getParameter("op");
PrintWriter out = response.getWriter();
if(checkcode.equals(verificationCode)){
out.println(1);
}else{
out.println(0);
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
4、效果
摘自：http://blog.csdn.net/weixian52034/article/details/52186207
时间： 2024-08-05 20:53:42