servlet+jsp实现验证码demo

package com.check; import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet("/ImageServlet") public class ImageServlet extends HttpServlet { private static final long serialVersionUID = 1L; public ImageServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //生成验证码，生成bufferdimage BufferedImage bi = new BufferedImage(68, 32, BufferedImage.TYPE_INT_RGB);//定义图片的高度和宽度 Graphics graphics=bi.getGraphics(); //画一个图片 Color color=new Color(200, 150, 255); graphics.setColor(color); graphics.fillRect(0, 0, 68, 32); List list=new ArrayList(); char[] num="1234567890".toCharArray(); char[] strUpper="ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray(); char[] strLower="abcdefghijklmnopqrstuvwxyz".toCharArray(); for (int i = 0; i < num.length; i++) { list.add(num[i]); } for (int i = 0; i < strUpper.length; i++) { list.add(strUpper[i]); } for (int i = 0; i < strLower.length; i++) { list.add(strLower[i]); } Object[] ch=list.toArray(); //char[] ch="1234567890".toCharArray(); //生成随机数 int len=ch.length,index; Random random=new Random(); StringBuffer sb=new StringBuffer(); for (int i = 0; i < 4; i++) { index=random.nextInt(len); //生成随即的字符，从char数组中获取，指定数组的长度 graphics.setColor( new Color( random.nextInt(88), random.nextInt(188), random.nextInt(255))); graphics.setFont(new Font("italic", Font.ITALIC, 20)); graphics.drawString(ch[index]+"", (i*15)+3, 18); sb.append(ch[index]); } request.getSession().setAttribute("piccode", sb.toString()); //将sb对象转为string类型进行验证 ImageIO.write(bi, "JPG", response.getOutputStream()); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }