在程序开发中往往会遇到为了防止别人恶意登陆而设置验证码，验证码是在程序界普遍应用很多，所以用户对验证码也很熟悉
工具/原料
myeclipse
新建servelet 类ImageRandServlet
1、新建一个servelet 名字叫ImageRandServlet
2、在doget方法中填写如下代码
3、ImageRandServlet 类的代码如下：import java.awt.Color;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.OutputStream;import java.util.Random;import java.awt.Font;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 ImageRandServlet extends HttpServlet { private static final String CONTENT_TYPE = "image/jpeg"; //Initialize global variables public void init() throws ServletException { } //Process the HTTP Get request public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { response.setHeader("Pragma", "No-cache"); response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expires", 0); int width = 60, height = 20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); OutputStream os = response.getOutputStream(); Graphics g = image.getGraphics(); Random random = new Random(); g.setColor(getRandColor(200, 250)); g.fillRect(0, 0, width, height); g.setFont(new Font("Arial", Font.PLAIN, 18)); g.setColor(getRandColor(160, 200)); 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); g.drawLine(x, y, x + xl, y + yl); } String sRand = ""; for (int j = 0; j < 4; j++) { String rand = String.valueOf(random.nextInt(10)); sRand += rand; g.setColor(new Color(20 + random.nextInt(110), 20 + random .nextInt(110), 20 + random.nextInt(110))); g.drawString(rand, 13 * j + 6, 16); } request.getSession().setAttribute("rand", sRand); g.dispose(); ImageIO.write(image, "JPEG", os); os.flush(); os.close(); os = null; response.flushBuffer(); // out.clear(); // out = pageContext.pushBody(); } catch (IllegalStateException e) { e.printStackTrace(); } } //Process the HTTP Post request public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } //Clean up resources public void destroy() { } 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); }}
新建test.jsp
1、新建test.jsp页面，此页面是来现实验证码的界面
2、在<body></body>之间添加如下代码：<img src="servlet/imageRandServlet">
3、jsp代码如下：<挢旗扦渌;%@ page language="java" import="j锾攒揉敫ava.util.*" pageEncoding="utf-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'test.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <img src="<%=basePath%>servlet/imageRandServlet"> </body></html>
servelet的web.xml配置
1、在WEB-INF目录下找到web.xml 在<web-app></web-app>节点之间添加<servlet> <servlet-name>imageRandServlet</servlet-name> <servlet-class>com.xianmeixian.util.ImageRandServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>imageRandServlet</servlet-name> <url-pattern>/servlet/imageRandServlet</url-pattern> </servlet-mapping>
2、运行程序，结果如下
