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);

        }

    }

}
           

<%@ 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>

<?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>

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");

        }

    }

}