java实现图片验证码
ImageGenerator 生成一张包含四位随机数的图片package com.my.page;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.OutputStream;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 这个class主要实现随机生成一个4位数的验证码，并写入session， */public class ImageGenerator extends HttpServlet {private static 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);}private static String charsLong = "23456789abcdefghjklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";private static String charsShort = "0123456789";private static String chars = charsLong;@Overridepublic void doGet(HttpServletRequest request, HttpServletResponse response) {try {int charsLength = chars.length();response.setHeader("Pragma", "No-cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expires", 0);int width = 75, height = 20;BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);Graphics g = image.getGraphics();Random random = new Random();g.setColor(getRandColor(200, 250));g.fillRect(0, 0, width, height);g.setFont(new Font("Times New Roman", Font.ITALIC, height));g.setColor(getRandColor(160, 200));for (int i = 0; i < 35; 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);}StringBuilder sRand = new StringBuilder();String[] fontNames = { "Times New Roman", "Arial", "Book antiqua","" }; for (int i = 0; i < 4; i++) {g.setFont(new Font(fontNames, Font.ITALIC,height));char rand = chars.charAt(random.nextInt(charsLength));sRand.append(rand);g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));g.drawString(String.valueOf(rand), 16 * i + random.nextInt(6)+ 3, height - random.nextInt(4));} g.setColor(getRandColor(160, 200)); for (int i = 0; i < 19; i++) {int x = random.nextInt(width);int y = random.nextInt(height);int xl = random.nextInt(width);int yl = random.nextInt(width);g.drawLine(x, y, x + xl, y + yl);} request.getSession().setAttribute("Login_Image_Code",sRand.toString()); g.dispose(); try {Thread.sleep(100);} catch (Exception ex) {}OutputStream os = response.getOutputStream();ImageIO.write(image, "JPEG", os);os.flush();os.close();} catch (Exception ex) { }}}
在web.xml加入一下内容
<servlet><servlet-name>imageGenerator</servlet-name><servlet-class>com.my.page.ImageGenerator</servlet-class></servlet> <servlet-mapping><servlet-name>imageGenerator</servlet-name><url-pattern>/image.jpg</url-pattern></servlet-mapping>
运用
<input type="text" class="txt" wicket:id="validate"/><br/><img src="/image.jpg" onclick= "this.src= '/image.jpg? '+(new Date()) "/>
其中onclick事件作用是：单击该验证图片，进行刷新，实现看不清换一张的效果
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