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注，本代码引用来之张孝祥的最新力作<深入体验java web开发内幕-核心基础>，保留所有权利。 此段servlet完整展示了动态验证码的生成过程，通俗易懂，不愧为张老师所写的代码，在此遇到一个问题，就是常说的javax.servlet包无法引入，我按要求都把servlet包放入了lib目录中，可还是一样找不到，因此实际调试效果还没看到。 首先是一个简单的登录页面。 Check_login.htm  <html> <head> <title>实现验证码功能</title> </head> <body> <h1>带有验证码功能的登录演示</h1> <form action="LogonFormServlet"> <table> <tr> <td>用户名：</td> <td><input type="text" name="userName"></td> </tr> <tr> <td>密码：</td> <td><input type="password" name="password"></td> </tr> <tr> <td>验证码：</td> <td><input type="text" value="mildo" name="passport"><img src="CheckCodeServlet"></td> </tr> <tr colspan="2"> <td><input type="submit" value="登录"></td> </tr> </table> </form></body></html>接下来就是生成图片验证码的Servlet了，源代码： CheckCodeServlet.java import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.awt.*;import java.awt.image.*;import javax.imageio.ImageIO;public class CheckCodeServlet extends HttpServlet...{ private static int WIDTH=60; private static int HIGHT=20; public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException ...{ HttpSession session = Request.session(); response.setContent("image/jpeg"); ServletOutputStream sos = response.getOutputStream(); //设置浏览器不要缓存图片 response.setHead("Pragma","No-cache"); response.setHead("Cache-Control","no-cache"); response.setDateHead("Expires",0); //创建内建图像，并获得上下文 BufferedImage image = new BufferedImage(WIDTH,HIGHT,BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); //生成随机认证码 char [] rands = new generateCheckCode(); //产生图像 drawBackgrounds(g); drawRands(g,rands); //结束图像绘制，完成输出 g.dispose(); //输出到客户端 ByteArrayOutputStream bos = new ByteArrayOutputStream(); ImageIO.write(image,"jpeg",bos); byte [] buf = bos.toByteArray(); response.setContentLength(buf.length); //下面的语句也可以写成 bos.write(sos); sos.wirte(buf); bos.close(); sos.close(); //将当前验证码插入到session中 session.setAttribute("check_code",new String(rands)); } private char[] generateCheckCode() ...{ //定义验证码的字符集 String str = "0123456789abcdefghjklmnopqrstuvwxyz"; char [] rands = new char[4]; for(int i=0;i<4;i++) ...{ int rand = (int)(Math.random()*36); rands[i] = chars.charAt(rand); } return rands; } private void drawRands(Graphics g,char[] rands) ...{ g.setColor(Color.black); g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18)); //在不同的高度输出验证码的字符 g.drawString(""+rands[0],1,16); g.drawString(""+rands[1],16,18); g.drawString(""+rands[2],32,15); g.drawString(""+rands[3],51,17); System.out.println(rands); } private void drawBackground(Graphics g) ...{ //画背景 g.setColor(Color.cyan); g.fillRect(0,0,WIDTH,HIGHT); //添加随机120个杂点 for(int i=0;i<120;i++) ...{ int x = (int)(Math.random()*WIDTH); int y = (int)(Math.random()*HIGHT); int red = (int)(Math.random()*255); int blue = (int)(Math.random()*255); int green = (int)(Math.random()*255); g.setColor(new Color(red,green,blue)); g.drawOval(x,y,1,0); } }}用来验证的servlet代码： LogonFormServlet.java import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.awt.*;import java.awt.image.*;import javax.imageio.ImageIO;public class CheckCodeServlet extends HttpServlet...{ private static int WIDTH=60; private static int HIGHT=20; public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException ...{ HttpSession session = Request.session(); response.setContent("image/jpeg"); ServletOutputStream sos = response.getOutputStream(); //设置浏览器不要缓存图片 response.setHead("Pragma","No-cache"); response.setHead("Cache-Control","no-cache"); response.setDateHead("Expires",0); //创建内建图像，并获得上下文 BufferedImage image = new BufferedImage(WIDTH,HIGHT,BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); //生成随机认证码 char [] rands = new generateCheckCode(); //产生图像 drawBackgrounds(g); drawRands(g,rands); //结束图像绘制，完成输出 g.dispose(); //输出到客户端 ByteArrayOutputStream bos = new ByteArrayOutputStream(); ImageIO.write(image,"jpeg",bos); byte [] buf = bos.toByteArray(); response.setContentLength(buf.length); //下面的语句也可以写成 bos.write(sos); sos.wirte(buf); bos.close(); sos.close(); //将当前验证码插入到session中 session.setAttribute("check_code",new String(rands)); } private char[] generateCheckCode() ...{ //定义验证码的字符集 String str = "0123456789abcdefghjklmnopqrstuvwxyz"; char [] rands = new char[4]; for(int i=0;i<4;i++) ...{ int rand = (int)(Math.random()*36); rands[i] = chars.charAt(rand); } return rands; }  private void drawRands(Graphics g,char[] rands)  ...{ g.setColor(Color.black); g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));  //在不同的高度输出验证码的字符 g.drawString(""+rands[0],1,16); g.drawString(""+rands[1],16,18); g.drawString(""+rands[2],32,15); g.drawString(""+rands[3],51,17); System.out.println(rands); }  private void drawBackground(Graphics g)  ...{ //画背景 g.setColor(Color.cyan); g.fillRect(0,0,WIDTH,HIGHT);  //添加随机120个杂点 for(int i=0;i<120;i++)  ...{ int x = (int)(Math.random()*WIDTH); int y = (int)(Math.random()*HIGHT); int red = (int)(Math.random()*255); int blue = (int)(Math.random()*255); int green = (int)(Math.random()*255);  g.setColor(new Color(red,green,blue)); g.drawOval(x,y,1,0); } } }这些做好了，当然要对servlet进行注册和映射了，web.xml  <servlet-name>CheckCodeServlet</servlet-name> <servlet-class>CheckCodeServlet</servlet-class> </servlet>  <servlet> <servlet-name>LogonFormServlet</servlet-name> <servlet-class>LogonFormServlet</servlet-class> </servlet>  <servlet-mapping> <serlet-name>CheckCodeServlet</serlet-name>  <url-pattern>/CheckCodeServlet</url-pattern> </servlet-mapping>  <servlet-mapping> <serlet-name>LogonFormServlet</serlet-name>  <url-pattern>/LogonFormServlet</url-pattern> </servlet-mapping> |
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来自： ShangShujie > 《java》
通过servlet生成随机验证码实例
