JSP验证码

 ImageServlet.java

package cn.hist.test.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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ImageServlet  extends HttpServlet{
    
    // 生成随机颜色  
    Color getRandColor(int fc, int bc) {  
        Random random = new Random();  
        if (fc > 255)  
            fc = 255;  
        if (bc > 255)  
            bc = 255;  
        int r = fc + random.nextInt(bc - fc);  
        int g = fc + random.nextInt(bc - fc);  
        int b = fc + random.nextInt(bc - fc);  
        return new Color(r, g, b);  
    } 
    
    public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
        HttpSession session = request.getSession();
        // 设置图形验证码中字符串的字体和大小  
        Font myFont = new Font("", Font.PLAIN, 25); 
        // 阻止生成的页面内容被缓存，保证每次重新生成随机验证码  
        response.setHeader("Pragma", "No-cache");  
        response.setHeader("Cache-Control", "no-cache");  
        response.setDateHeader("Expires", 0);  
        response.setContentType("image/jpeg");
        // 指定图形验证码图片的大小
        int width = 64, height = 41;
        // 生成一张新图片
        BufferedImage image=new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
        Graphics g=image.getGraphics(); //通过缓冲区创建一个画布
        Random random = new Random();
        g.setColor(getRandColor(200, 250));//为画布创建背景颜色
        g.fillRect(0, 0, width,height); //fillRect:填充指定的矩形
        g.setColor(new Color(82, 82, 82));  //字体颜色
        //g.drawRect(0, 0, width - 1, height - 1); //产生边框
        g.setFont(myFont);
        // 随机生成线条，让图片看起来更加杂乱  
        g.setColor(getRandColor(160, 200));  
        for (int i = 0; i < 155; i++) {  
            int x = random.nextInt(width - 1);// 起点的x坐标  
            int y = random.nextInt(height - 1);// 起点的y坐标  
            int x1 = random.nextInt(6) + 1;// x轴偏移量  
            int y1 = random.nextInt(12) + 1;// y轴偏移量  
            g.drawLine(x, y, x + x1, y + y1);  
        }   
        // 随机生成线条，让图片看起来更加杂乱  
        for (int i = 0; i < 70; i++) {  
            int x = random.nextInt(width - 1);  
            int y = random.nextInt(height - 1);  
            int x1 = random.nextInt(12) + 1;  
            int y1 = random.nextInt(6) + 1;  
            g.drawLine(x, y, x - x1, y - y1);  
        } 
        // 该变量用来保存系统生成的随机字符串  
        String sRand = "";  
        for (int i = 0; i < 6; i++) {  
            // 取得一个随机字符  
            String tmp = getRandomChar();  
            sRand += tmp;  
            // 将系统生成的随机字符添加到图形验证码图片上  
            g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
            //将验证码显示在图像中
            g.drawString(tmp, 15 * i + 3, 30);  //字体距左边及上边的距离
        }  
         
        // 将系统生成的图形验证码添加  
        session.setAttribute("rand", sRand);  
        g.dispose();  
        // 输出图形验证码图片  
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }
    // 随机生成一个字符  
    private String getRandomChar() {  
        int rand = (int) Math.round(Math.random() * 2);// 将0～2的小数四舍五入生成整数  
        long itmp = 0;  
        char ctmp = 'u0000';  
        // 根据rand的值来决定是生成一个大写字母、小写字母和数字  
        switch (rand) {  
        // 生成大写字母的情形  
        case 1:  
            itmp = Math.round(Math.random() * 25 + 65);  
            ctmp = (char) itmp;  
            return String.valueOf(ctmp);  
            // 生成小写字母  
        case 2:  
            itmp = Math.round(Math.random() * 25 + 97);  
            ctmp = (char) itmp;  
            return String.valueOf(ctmp);  
            // 生成数字  
        default:  
            itmp = Math.round(Math.random() * 9);  
            return String.valueOf(itmp);  
        }  
    }  
}  
           

index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<base href="<%=basePath%>">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>Test</title>
<link rel="stylesheet" href="">
<script>
    //刷新验证码
    function refresh() {
        var time = new Date().getTime();
        document.getElementById("imagecode").src = "ImageServlet?d=" + time;
    }
</script>
</head>
<body>
    <form action="ImageCompare">
        <p>
            <label for="icode">验证码</label><input type="text" name="icode"
                id="icode" placeholder="请输入验证码" /><img alt="验证码"
                id="imagecode" class="imagecode" src="ImageServlet"
                onclick="refresh()" /><a href="javascript:void(0);"
                onclick="refresh()">看不清？</a>
        </p>
    </form>
</body>
</html>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <display-name></display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>ImageServlet</servlet-name>
        <servlet-class>cn.hist.test.servlet.ImageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ImageServlet</servlet-name>
        <url-pattern>/ImageServlet</url-pattern>
    </servlet-mapping>
</web-app>

ImageCompare.java

package cn.hist.test.servlet;

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;
import javax.servlet.http.HttpSession;

/**
 * 比较输入的验证码是否正确
 * @author Administrator
 *
 */
public class ImageCompare extends HttpServlet{
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        PrintWriter out = resp.getWriter();
        HttpSession session = req.getSession();
        // 获取验证码中的字符
        String rand = (String) session.getAttribute("rand");
        System.out.println(rand);
        String icode = req.getParameter("icode");
        System.out.println(icode);
        if (icode.equals(rand)) {
            out.print("success");
        }
        else {
            out.print("fail");
        }
    }
}

 将rand与icode都转换成大写或小写再进行比较，实现输入验证码时不区分大小写