JSP + Servlet实现生成登录验证码示例

package servlet;import java.awt.BasicStroke;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.geom.AffineTransform;import java.awt.geom.Line2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;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;import javax.servlet.http.HttpSession;public class PictureCheckCode extends HttpServlet {   private static final long serialVersionUID = 1L;     public PictureCheckCode() {       super();     }     public void destroy() {       super.destroy();      }     public void init() throws ServletException {       super.init();     }     /*该方法主要作用是获得随机生成的颜色*/      public Color getRandColor(int s,int e){       Random random=new Random ();       if(s>255) s=255;       if(e>255) e=255;       int r,g,b;       r=s+random.nextInt(e-s);  //随机生成RGB颜色中的r值       g=s+random.nextInt(e-s);  //随机生成RGB颜色中的g值       b=s+random.nextInt(e-s);  //随机生成RGB颜色中的b值       return new Color(r,g,b);     }   public void doGet(HttpServletRequest request, HttpServletResponse response)      throws ServletException, IOException {    System.out.println("this is doGet method");    this.doPost(request, response);  }  public void doPost(HttpServletRequest request, HttpServletResponse response)      throws ServletException, IOException {    //设置不缓存图片     response.setHeader("Pragma", "No-cache");     response.setHeader("Cache-Control", "No-cache");     response.setDateHeader("Expires", 0);     //指定生成的响应图片,一定不能缺少这句话,否则错误.     response.setContentType("image/jpeg");     int width=80,height=35;   //指定生成验证码的宽度和高度     BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //创建BufferedImage对象,其作用相当于一图片     Graphics g=image.getGraphics();   //创建Graphics对象,其作用相当于画笔     Graphics2D g2d=(Graphics2D)g;    //创建Grapchics2D对象     Random random=new Random();     Font mfont=new Font("楷体",Font.BOLD,16); //定义字体样式     g.setColor(getRandColor(200,250));     g.fillRect(0, 0, width, height);  //绘制背景     g.setFont(mfont);          //设置字体     g.setColor(getRandColor(180,200));     //绘制100条颜色和位置全部为随机产生的线条,该线条为2f     for(int i=0;i<100;i++){       int x=random.nextInt(width-1);       int y=random.nextInt(height-1);       int x1=random.nextInt(6)+1;       int y1=random.nextInt(12)+1;       BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定制线条样式       Line2D line=new Line2D.Double(x,y,x+x1,y+y1);       g2d.setStroke(bs);       g2d.draw(line);   //绘制直线     }     //输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。     String sRand="";     String ctmp="";     int itmp=0;     //制定输出的验证码为四位     for(int i=0;i<4;i++){       switch(random.nextInt(3)){         case 1:   //生成A-Z的字母            itmp=random.nextInt(26)+65;            ctmp=String.valueOf((char)itmp);            break;         case 2:   //生成汉字            String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};             //生成第一位区码            int r1=random.nextInt(3)+11;            String str_r1=rBase[r1];            //生成第二位区码            int r2;            if(r1==13){              r2=random.nextInt(7);              }else{              r2=random.nextInt(16);            }            String str_r2=rBase[r2];            //生成第一位位码            int r3=random.nextInt(6)+10;            String str_r3=rBase[r3];            //生成第二位位码            int r4;            if(r3==10){              r4=random.nextInt(15)+1;            }else if(r3==15){              r4=random.nextInt(15);            }else{              r4=random.nextInt(16);            }            String str_r4=rBase[r4];            //将生成的机内码转换为汉字            byte[] bytes=new byte[2];            //将生成的区码保存到字节数组的第一个元素中            String str_12=str_r1+str_r2;            int tempLow=Integer.parseInt(str_12, 16);            bytes[0]=(byte) tempLow;            //将生成的位码保存到字节数组的第二个元素中            String str_34=str_r3+str_r4;            int tempHigh=Integer.parseInt(str_34, 16);            bytes[1]=(byte)tempHigh;            ctmp=new String(bytes);            break;         default:            itmp=random.nextInt(10)+48;            ctmp=String.valueOf((char)itmp);            break;       }       sRand+=ctmp;       Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110));       g.setColor(color);       //将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示       /*将文字旋转制定角度*/       Graphics2D g2d_word=(Graphics2D)g;       AffineTransform trans=new AffineTransform();       trans.rotate((45)*3.14/180,15*i+8,7);       /*缩放文字*/       float scaleSize=random.nextFloat()+0.8f;       if(scaleSize>1f) scaleSize=1f;       trans.scale(scaleSize, scaleSize);       g2d_word.setTransform(trans);       g.drawString(ctmp, 15*i+18, 14);     }     HttpSession session=request.getSession(true);     session.setAttribute("randCheckCode", sRand);     System.out.println(sRand);    g.dispose();  //释放g所占用的系统资源     ImageIO.write(image,"JPEG",response.getOutputStream()); //输出图片   }}

<servlet>  <description>This is the description of my J2EE component</description>  <display-name>This is the display name of my J2EE component</display-name>  <servlet-name>PictureCheckCode</servlet-name>  <servlet-class>servlet.PictureCheckCode</servlet-class> </servlet><servlet-mapping>  <servlet-name>PictureCheckCode</servlet-name>  <url-pattern>/pictureCheckCode</url-pattern> </servlet-mapping>

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>登录页面</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"><script language="javascript">  function myReload() {    document.getElementById("CreateCheckCode").src = document        .getElementById("CreateCheckCode").src        + "?nocache=" + new Date().getTime();  }</script></head><body>  <form action="loginServlet" method="get">      <p class="font tdheight">        验证码：<input type="text" name="checkCode"          style="width:70px;height:35px;"> <img          src="pictureCheckCode" id="CreateCheckCode" align="middle"          style="margin-top:-10px;"> <br> <a href=""          onclick="myReload()"          style="font-size:12px;color:red;margin-left:156px;"> 看不清,换一个</a>      </p>      <br><input type="submit" value="提交"            class="font" style="width:240px;height:35px;background:#f19e28">    </form></body></html>

public void doGet(HttpServletRequest request, HttpServletResponse response)      throws ServletException, IOException {    String code = request.getParameter("checkCode");    HttpSession session = request.getSession();    if (!code.equals(session.getAttribute("randCheckCode"))) {      request.setAttribute("errormsg", "验证码不正确");    }     System.out.println(request.getAttribute("errormsg"));  }