jsp登陆页面:
<html>
<head>
<title>验证码</title>
<script type="text/javascript">
function again(obj) {
obj.src = "imageServlet?"+Math.random();
}
</script>
</head>
<body>
<center>
<form action="checkServlet.jsp" method="post">
<label>用户名:</label><input type="text" name="user"/><br><br>
<label>密 码:</label><input type="password" name="pwd"/><br>
<label>验证码:</label>
<input type="text" name="randomCode" value="区分大小写"/> <img title="点击更换" onclick="javascript:again(this);" src="imageServlet"><br/>
<input type="submit" value="submit">
</form>
</center>
</body>
</html>
jsp的验证页面(部分)：
<body>
<sql:query var="result" dataSource="${dbs }">
select name,password from user
</sql:query>
<c:set var="user" value="${result.rows[0].name }"></c:set>
<c:set var="password" value="${result.rows[0].password }"></c:set>
<c:set var="checkcode" value="${param.randomCode }"></c:set>
<c:set var="session" value="${sessionScope.RANDOMVALIDATECODEKEY }"></c:set>
<c:if test="${password==param.pwd }">
<c:if test="${user==param.user }">
<c:if test="${session==checkcode }">
<c:redirect url="http://localhost:8080/ToTal/Alltogether.jsp"></c:redirect>
</c:if>
</c:if>
</c:if>
</body>
验证码的制作（借鉴他人的）：
serlet：
package com.wf.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ImageServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片
response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expire", 0);
RandomValidateCode randomValidateCode = new RandomValidateCode();
try {
randomValidateCode.getRandcode(request, response);//输出图片方法
} catch (Exception e) {
e.printStackTrace();
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
生成随机数字和字母图片：
package com.wf.web;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class RandomValidateCode {
public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";//放到session中的key
private Random random = new Random();
private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串
private int width = 80;//图片宽
private int height = 26;//图片高
private int lineSize = 40;//干扰线数量
private int stringNum = 4;//随机产生字符数量
/*
* 获得字体
*/
private Font getFont(){
return new Font("Fixedsys",Font.CENTER_BASELINE,18);
}
/*
* 获得颜色
*/
private Color getRandColor(int fc,int bc){
if(fc > 255)
fc = 255;
if(bc > 255)
bc = 255;
int r = fc + random.nextInt(bc-fc-16);
int g = fc + random.nextInt(bc-fc-14);
int b = fc + random.nextInt(bc-fc-18);
return new Color(r,g,b);
}
/**
* 生成随机图片
*/
public void getRandcode(HttpServletRequest request,
HttpServletResponse response) {
HttpSession session = request.getSession();
//BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
Graphics g = image.getGraphics();//产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18));
g.setColor(getRandColor(110, 133));
//绘制干扰线
for(int i=0;i<=lineSize;i++){
drowLine(g);
}
//绘制随机字符
String randomString = "";
for(int i=1;i<=stringNum;i++){
randomString=drowString(g,randomString,i);
}
session.removeAttribute(RANDOMCODEKEY);
session.setAttribute(RANDOMCODEKEY, randomString);//将生成的随机数字和字母图片放在session中，
//以供在验证登陆中取出和用户输入的文本内容比较（大小写区分）
System.out.println(randomString);
g.dispose();
try {
ImageIO.write(image, "JPEG", response.getOutputStream());//将内存中的图片通过流动形式输出到客户端
} catch (Exception e) {
e.printStackTrace();
}
}
/*
* 绘制字符串
*/
private String drowString(Graphics g,String randomString,int i){
g.setFont(getFont());
g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121)));
String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
randomString +=rand;
g.translate(random.nextInt(3), random.nextInt(3));
g.drawString(rand, 13*i, 16);
return randomString;
}
/*
* 绘制干扰线
*/
private void drowLine(Graphics g){
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(13);
int yl = random.nextInt(15);
g.drawLine(x, y, x+xl, y+yl);
}
/*
* 获取随机的字符
*/
public String getRandomString(int num){
return String.valueOf(randString.charAt(num));
}
}