本文介绍了一个简单的验证码生成系统实现，包括生成带有随机干扰线的图片验证码，并通过Servlet和JSP技术将其集成到Web应用中进行用户输入验证。该系统利用Java图形库绘制验证码并保存在会话中，以便后续验证。
------------产生验证码图片的文件-----image.servlet-------------------------------------------
package untitled1;import java.io.*;import java.net.*;import javax.servlet.*;import javax.servlet.http.*;import java.awt.*;import java.awt.image.*;import java.util.*;import javax.imageio.*;
/** *//**
* * @author http://www.tot.name * @version
*/public class Image extends HttpServlet ...{
/** *//** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods. * @param request servlet request * @param response servlet response
*/ protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException ...{ response.setContentType("image/jpeg"); response.setHeader("Pragma","No-cache"); response.setHeader("Cache-Control","no-cache"); response.setDateHeader("Expires", 0); HttpSession session=request.getSession(); // 在内存中创建图象 int width=60, height=20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 获取图形上下文 Graphics g = image.getGraphics(); //生成随机类 Random random = new Random(); // 设定背景色 g.setColor(getRandColor(200,250)); g.fillRect(0, 0, width, height); //设定字体 g.setFont(new Font("Times New Roman",Font.PLAIN,18)); //画边框 //g.setColor(new Color()); //g.drawRect(0,0,width-1,height-1); // 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 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); } // 取随机产生的认证码(4位数字) String sRand=""; for (int i=0;i<4;i++)...{ String rand=String.valueOf(random.nextInt(10)); sRand+=rand; // 将认证码显示到图象中 g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 g.drawString(rand,13*i+6,16); } // 将认证码存入SESSION session.setAttribute("rand",sRand); // 图象生效 g.dispose(); ServletOutputStream responseOutputStream =response.getOutputStream(); // 输出图象到页面 ImageIO.write(image, "JPEG", responseOutputStream); //以下关闭输入流！ responseOutputStream.flush(); responseOutputStream.close(); } Color getRandColor(int fc,int bc)...{//给定范围获得随机颜色 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); } // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> /** *//** Handles the HTTP <code>GET</code> method. * @param request servlet request * @param response servlet response */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException ...{ processRequest(request, response); } /** *//** Handles the HTTP <code>POST</code> method. * @param request servlet request * @param response servlet response */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException ...{ processRequest(request, response); } /** *//** Returns a short description of the servlet. */ public String getServletInfo() ...{ return "Short description"; } // </editor-fold>}<%...@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %><html><head><title>认证码验证页面</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><META HTTP-EQUIV="Pragma" CONTENT="no-cache"> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> <META HTTP-EQUIV="Expires" CONTENT="0"> </head><body><%... String rand = (String)session.getAttribute("rand");String input = request.getParameter("rand");%>系统产生的认证码为： <%= rand %><br>您输入的认证码为： <%= input %><br><br><%... if (rand.equals(input)) {%><font color=green>输入相同，认证成功！</font><%... } else {%><font color=red>输入不同，认证失败！</font><%
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