java实现图片验证码

这段时间一直在忙着搞课设，没顾得上写，今天终于找到了一点时间，赶快开写啦~

ImageServlet.java（image.do）：用于生成验证码图片

package com.ymw.web.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.ServletOutputStream;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 {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {int width = 80;// 验证码图片宽度int height = 26;// 验证码图片高度BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_3BYTE_BGR);Graphics g = image.getGraphics();Random random = new Random();// 创建一个随机类g.setColor(getRandColor(200, 250));// 背景颜色要偏淡g.fillRect(0, 0, width, height);// 画背景g.setColor(getRandColor(0, 255));// 边框颜色g.drawRect(0, 0, width - 1, height - 1);// 画边框g.setColor(getRandColor(160, 200));// 随机产生5条干扰线，使图象中的认证码不易被其它程序探测到for (int i = 0; i < 8; i++) {int x = random.nextInt(width);int y = random.nextInt(height);int x1 = random.nextInt(width);int y1 = random.nextInt(height);g.drawLine(x, y, x1, y1);}g.setColor(getRandColor(160, 200));// 随机产生100点，使图象中的认证码不易被其它程序探测到for (int i = 0; i < 100; i++) {int x = random.nextInt(width);int y = random.nextInt(height);g.drawLine(x, y, x, y);}Font font = new Font("Times New Roman", Font.ITALIC, 20); // 创建字体，字体的大小应该根据图片的高度来定。g.setFont(font);// 设置字体int length = 4; // 设置默认生成4个验证码String s = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; // 设置备选验证码:包括"a-z"和数字"0-9"String sRand = "";// 用随机产生的颜色将验证码绘制到图像中。// 生成随机颜色(因为是做前景，所以偏深)// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成g.setColor(new Color(20 + random.nextInt(110),20 + random.nextInt(110), 20 + random.nextInt(110)));for (int i = 0; i < length; i++) {String ch = String.valueOf(s.charAt(random.nextInt(s.length())));sRand += ch;g.drawString(ch, 11 * i + 12, (random.nextInt(5) - 2) * i + 20);}// 将生成的字符串存储在session中（这点很重要！之后验证时要用到！）HttpSession session = request.getSession();session.setAttribute("checkCode", sRand);g.dispose();// 图像生效// 禁止图像缓存response.setHeader("Pragma", "No-cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expires", 0);response.setContentType("image/jpeg");// 创建二进制的输出流ServletOutputStream sos = response.getOutputStream();// 将图像输出到Servlet输出流中。ImageIO.write(image, "jpeg", sos);sos.flush();sos.close();}public Color getRandColor(int lower, int upper) {Random random = new Random();if (upper > 255)upper = 255;if (upper < 1)upper = 1;if (lower < 1)lower = 1;if (lower > 255)lower = 255;int r = lower + random.nextInt(upper - lower);int g = lower + random.nextInt(upper - lower);int b = lower + random.nextInt(upper - lower);return new Color(r, g, b);}}

<script>function changeImage(){var obj = document.getElementById("image");obj.src = "image.do?r="+Math.random();}</script>。。。<tr><td class="field">验证码：</td><td><input type="text" name="veryCode" /><img id="image" src="image.do" /><a onclick="changeImage()" style="cursor:pointer">看不清楚？点击这里更换</a><br />${imageCodeResult }</td></tr>

style=”cursor:pointer”鼠标移上是手型；

LoginServlet.java：用于处理login.jsp提交上来的请求

public class LoginServlet extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {request.setCharacterEncoding("utf-8");//解决乱码问题String veryCode = request.getParameter("veryCode");//得到用户输入的验证码//先将从session中获取的验证码与用户输入的验证码进行比较，如果相同再验证用户名和密码，否则将错误信息带回登陆界面if(veryCode.equals(session.getAttribute("checkCode"))){//进行其他信息的验证}else {String imageCodeResult="验证码输入错误，请重新输入！";//千万不要忘记把表示验证情况的信息放到request中去，否则前台是不能看到的request.setAttribute("imageCodeResult", imageCodeResult);request.getRequestDispatcher("login.jsp").forward(request, response);}} }