Java web验证码

绘制验证码的主要步骤：

　　　1，设置宽度高度，验证码个数，干扰线个数，可选字符，背景颜色，字体格式

　　　2，画干扰线，随机生成颜色，字体，字符

　　　3，设置缓冲区，得到画笔，设置边框，读写数据，存储图片。

1,Servlet方法：

　　CheckCodeServlet类：

package org.servlet;

import java.io.IOException;
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 java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpSession;

import sun.java2d.loops.DrawLine;

/**
 * 输出随机的验证码
 */
@WebServlet({ "/CheckCode", "/checkCode.jpg" })
public class CheckCodeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /* 宽度 */
    private final int WIDTH = 200;
    /* 高度 */
    private final int HEIGHT = 40;
    /* 生成验证码的个数 */
    private final int COUNT = 4;
    /* 干扰线条数 */
    private final int LINE_ROW = 6;

    /* 输出的基本码表，如果使用中文，则使用utf-8的码表，类似 \ue234 ，而且应该使用常用字，避免出现偏僻字 */
    private final char[] BASECODE = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
            'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u',
            'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
            'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U',
            'V', 'W', 'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7',
            '8', '9' };

    // 写出数据
    private void write(HttpServletRequest request, HttpServletResponse response)
            throws IOException {
        HttpSession session = request.getSession();

        BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
                BufferedImage.TYPE_INT_RGB);
        Graphics graphics = image.getGraphics();

        setBackground(graphics);
        drawBorder(graphics);
        drawDot(graphics);
        drawLine(graphics);
        drawString(graphics, session);

        // 写出数据流
        ImageIO.write(image, "jpg", response.getOutputStream());

    }

    // 写字
    private void drawString(Graphics graphics, HttpSession session) {
        StringBuffer sb = new StringBuffer();
        Random random = new Random();

        graphics.setFont(new Font("宋体", Font.BOLD, 18));
        graphics.setColor(Color.BLACK);

        for (int i = 0; i < COUNT; i++) {
            String ch = String
                    .valueOf(BASECODE[random.nextInt(BASECODE.length)]);
            sb.append(ch);

            // 设置位置
            int x = i * 20 + random.nextInt(12) + 10;
            int y = random.nextInt(HEIGHT / 3) + 12;

            // 旋转字体
            double theta = Math.PI / 180 * random.nextInt(20);
            // rotate(graphics, theta);

            graphics.drawString(ch, x, y);

            // 恢复。。
            // rotate(graphics, -theta);
        }
        session.setAttribute("checkCode", sb.toString());

        System.out.println("   验证码：" + sb.toString());
    }

    // 旋转
    private void rotate(Graphics graphics, double theta) {
        ((Graphics2D) graphics).rotate(theta);
    }

    // 画随机线条
    private void drawLine(Graphics graphics) {
        Random random = new Random();
        for (int i = 0; i < LINE_ROW; i++) {
            int x1 = random.nextInt(WIDTH);
            int y1 = random.nextInt(HEIGHT);
            int x2 = random.nextInt(WIDTH);
            int y2 = random.nextInt(HEIGHT);
            setRandomColor(graphics);
            graphics.drawLine(x1, y1, x2, y2);
        }
    }

    // 画斑点
    private void drawDot(Graphics graphics) {
        Random random = new Random();
        graphics.setColor(Color.red);
        for (int i = 0; i < WIDTH; i++) {
            int x = i;
            int y = random.nextInt(HEIGHT);
            int r = random.nextInt(2);
            // graphics.fillOval(x, y, r, r);
            graphics.drawOval(x, y, r, r);
        }
    }

    // 画边框
    private void drawBorder(Graphics graphics) {
        graphics.setColor(Color.BLACK);
        graphics.drawRect(1, 1, WIDTH - 2, HEIGHT - 2);
    }

    // 设置背景
    private void setBackground(Graphics graphics) {
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, WIDTH, HEIGHT);// 填充背景色
    }

    // 设置随机的画笔颜色
    private void setRandomColor(Graphics g) {
        Random random = new Random();
        g.setColor(new Color(random.nextInt(255), random.nextInt(255), random
                .nextInt(255)));
    }

    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {

        // 输出图片流的头信息
        response.setContentType("image/jpeg");
        response.setHeader("Expires", "-1");
        response.setHeader("Cache-Control", "no-cache");

        // 写出数据
        write(request, response);

    }

    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}
　　

2,XML文件配置：

　　　　将CheckCodeServlet写入配置。

3，jsp文件显示验证码：

　　　　

<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <script type="text/javascript">
        function flushCheckCode(obj) {
            obj.src = (obj.src + '?' + new Date())
        }
    </script>
</head>
<body>
	<form action="LoginServlet" method="post" align="center">
	<table align="center">
	    <caption><p class="text1">用户登陆</p></caption>
	       <tr>
	         <td>
	                           用户名：
	         </td>
	         <td>
	           <input name="username" type="text" placeholder="Userneme">
	         </td>
	       </tr>
	       <tr>
	        <td>
	                            密 码:
	        </td>
	        <td>
	           <input name="password" type="password"  placeholder="Password">
	        </td>
	       </tr>
	       <tr>
	       <td>
	                       验证码：
	       </td>
	       <td>
           <input type="text" name="checkCode" placeholder="CheckCode"/>
           </td>
           </tr>
           </table>
           <tr>
           <td>
                          
           <img src="checkCode.jpg" onclick=flushCheckCode(this) alt="点击刷新验证码" />
	       </td>
	       </tr>
	       <br/>
	       <input name="submit" type="submit" class="button" value="登陆"/></br>
	       <p class="text2"><a href="register.jsp">没有账号？来注册一个吧！</a></font></p>
	</form>
</body>
</html>