JSP验证码生成 点击按钮更新

点击“看不清换一张”

测试用例：

Index.jsp

package javaServlet;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.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class ImageMaskServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setHeader("Pragma", "No-cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expires", 0);int width = 60, height = 20;//创建图象 BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);//获取图形上下文 Graphics graphics = image.getGraphics();//生成随机类Random random = new Random();//设定背景色 graphics.setColor(getRandColor(200, 250));//验证码大小graphics.fillRect(0, 0, width, height);//设置字体graphics.setFont(new Font("Times New Roman", Font.PLAIN, 18));    //graphics.setColor(getRandColor(160, 200));//随机产生155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 < 155; i++) {int x = random.nextInt(width);int y = random.nextInt(height);int xl = random.nextInt(12);int yl = random.nextInt(12);graphics.drawLine(x, y, x + xl, y + yl);}//取随机产生的认证码(4位数字) String sRand = "";for (int i = 0; i < 4; i++) {//0~9String rand = String.valueOf(random.nextInt(10));sRand += rand;//设置数字颜色graphics.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));//把随机产生的4位数画在图片上graphics.drawString(rand, 13 * i + 6, 16);}//放在session中request.getSession().setAttribute("imageMask", sRand);//图象生效 graphics.dispose();//输出图象到页面 ImageIO.write(image, "JPEG", response.getOutputStream());}//生成随机颜色public 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);}}