验证码：快速操作，简单易懂

CodeServlet：package com.lxs.servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.OutputStream;import java.util.Random;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 CodeServlet extends HttpServlet {private static final long serialVersionUID = 1L;protected void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String codes="abcdefghijklmnopqrstuvwxyzABCDEFJHIJKLMNOPQRSTUVWXYZ0123456789";BufferedImage img=new BufferedImage(80,30,BufferedImage.TYPE_3BYTE_BGR);Graphics g=img.getGraphics();//填充图片g.setColor(new Color(255,255,255));g.fillRect(0, 0, 80, 30);//画入五个随机数Random rm=new Random();StringBuffer sb=new StringBuffer();for(int i=0;i<5;i++){int index=rm.nextInt(codes.length());char code=codes.charAt(index);g.setColor(new Color(rm.nextInt(256),rm.nextInt(256),rm.nextInt(256)));g.setFont(new Font("宋体", Font.BOLD, 25));g.drawString(code+"", 2+15*i, 22);sb.append(code);}//画干扰线for(int i=0;i<10;i++){g.setColor(new Color(rm.nextInt(256),rm.nextInt(256),rm.nextInt(256)));g.drawLine(rm.nextInt(100), rm.nextInt(50), rm.nextInt(100), rm.nextInt(50));}//将验证码图片回写给浏览器response.setContentType("image/jpeg;charset=utf-8");OutputStream out=response.getOutputStream();ImageIO.write(img, "jpeg", out);//将随机字符串保存在session中request.getSession().setAttribute("code", sb.toString());}}image.jsp：<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="utf-8"%><%!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);}%><%out.clear();                           /*这句针对resin服务器，如果是tomacat可以不要这句*/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);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.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 i=0;i<4;i++){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*i+6,16);}// 将认证码存入SESSIONsession.setAttribute("sRand",sRand);g.dispose();ImageIO.write(image, "JPEG", response.getOutputStream());%>使用方法：第一种:image.jsp<script type="text/javascript">         function loadImage(){     document.getElementById("randImage").src = "${pageContext.request.contextPath}/image.jsp?"+Math.random(); //Math.random()方法非常重要，它使每次的请求都不同以便重新发送。如果每次的请求都一样，那么不会重新生成页面         }      </script> <img onClick="javascript:loadImage();"  title="换一张试试" id="randImage"           src="${pageContext.request.contextPath}/image.jsp"  border="1" >第二种：servlet方式 <servlet-name>CodeServlet</servlet-name>    <servlet-class>com.yinhe.web.servlet.CodeServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>CodeServlet</servlet-name>    <url-pattern>/checkCode</url-pattern>  </servlet-mapping><img src="checkCode" alt="" id="codeImg"style="width: 80px; height: 30px; border: 1px solid black;" /> <a href="javascript:;" onclick="document.getElementById('codeImg').src = 'checkCode?'+(new Date()).getTime()">换一张</a><span id="codemsg" style="color: red; font-size: 20px;"></span>

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