java登录验证码实现代码

package com.spring.controller;import java.awt.Color;         import java.awt.Font;         import java.awt.Graphics2D;         import java.awt.image.BufferedImage;         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;  import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;@Controllerpublic class VerifyCodeServlet extends HttpServlet {  // 验证码图片的宽度。             private int width = 60;             // 验证码图片的高度。             private int height = 20;             // 验证码字符个数             private int codeCount = 4;             private int x = 0;             // 字体高度             private int fontHeight;             private int codeY;             char[] codeSequence = { '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' };             /**            * 初始化验证图片属性            */            public void initxuan() throws ServletException {                 // 从web.xml中获取初始信息                 // 宽度                 String strWidth ="80";                 // 高度                 String strHeight ="30";                 // 字符个数                 String strCodeCount = "4";                 // 将配置的信息转换成数值                 try {                     if (strWidth != null && strWidth.length() != 0) {                         width = Integer.parseInt(strWidth);                     }                     if (strHeight != null && strHeight.length() != 0) {                         height = Integer.parseInt(strHeight);                     }                     if (strCodeCount != null && strCodeCount.length() != 0) {                         codeCount = Integer.parseInt(strCodeCount);                     }                 } catch (NumberFormatException e) {                 }                 x = width / (codeCount + 1);                 fontHeight = height - 2;                 codeY = height - 4;             }       @RequestMapping(value="xuan/verifyCode",method=RequestMethod.GET)    public void service(HttpServletRequest req, HttpServletResponse resp)                     throws ServletException, java.io.IOException {         initxuan();        // 定义图像buffer                 BufferedImage buffImg = new BufferedImage(width, height,                         BufferedImage.TYPE_INT_RGB);                 Graphics2D g = buffImg.createGraphics();                 // 创建一个随机数生成器类                 Random random = new Random();                 // 将图像填充为白色                 g.setColor(Color.WHITE);                 g.fillRect(0, 0, width, height);                 // 创建字体，字体的大小应该根据图片的高度来定。                 Font font = new Font("Fixedsys", Font.PLAIN, fontHeight);                 // 设置字体。                 g.setFont(font);                 // 画边框。                 g.setColor(Color.BLACK);                 g.drawRect(0, 0, width - 1, height - 1);                 // 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。                 g.setColor(Color.BLACK);                 for (int i = 0; i < 10; i++) {                     int x = random.nextInt(width);                     int y = random.nextInt(height);                     int xl = random.nextInt(12);                     int yl = random.nextInt(12);                     g.drawLine(x, y, x + xl, y + yl);                 }                 // randomCode用于保存随机产生的验证码，以便用户登录后进行验证。                 StringBuffer randomCode = new StringBuffer();                 int red = 0, green = 0, blue = 0;                 // 随机产生codeCount数字的验证码。                 for (int i = 0; i < codeCount; i++) {                     // 得到随机产生的验证码数字。                     String strRand = String.valueOf(codeSequence[random.nextInt(36)]);                     // 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。                     red = random.nextInt(255);                     green = random.nextInt(255);                     blue = random.nextInt(255);                     // 用随机产生的颜色将验证码绘制到图像中。                     g.setColor(new Color(red, green, blue));                     g.drawString(strRand, (i + 1) * x, codeY);                     // 将产生的四个随机数组合在一起。                     randomCode.append(strRand);                 }                 // 将四位数字的验证码保存到Session中。                 HttpSession session = req.getSession();                 session.setAttribute("validateCode", randomCode.toString());                 // 禁止图像缓存。                 resp.setHeader("Pragma", "no-cache");                 resp.setHeader("Cache-Control", "no-cache");                 resp.setDateHeader("Expires", 0);                 resp.setContentType("image/jpeg");                 // 将图像输出到Servlet输出流中。                 ServletOutputStream sos = resp.getOutputStream();                 ImageIO.write(buffImg, "jpeg", sos);                 sos.close();             }         }