项目结构如图一：
第一步，新建PictureCode.java：
package com.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.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 PictureCode extends HttpServlet{ @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //设置不缓存 resp.setHeader("pragma", "no-cache"); resp.setHeader("cache-control", "no-cache"); resp.setDateHeader("expires", 0); //指定生成的图片的格式 resp.setContentType("image/jpeg"); //验证码的张宽 int width=80,height=30; //图片流 BufferedImage image=new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR); 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 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 Random random=new Random(); 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); Line2D line2d=new Line2D.Double(x,y,x+x1,y+y1); g2d.setStroke(bs); g2d.draw(line2d); } //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++){ //random.nextInt(2)在0-2中间去随机，不包含2，这样是为了下面不去生成中文验证码，验证出现中文时，不好判断 switch(random.nextInt(2)){ case 1: //生成A-Z的字母 itmp=random.nextInt(26)+65; ctmp=String.valueOf((char)itmp); 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); } //打开session，并放入验证图片 HttpSession session=req.getSession(true); session.setAttribute("randCheckCode", sRand); g.dispose(); //释放g所占用的系统资源 ImageIO.write(image,"JPEG",resp.getOutputStream()); //输出图片 } public PictureCode() { super(); } public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } 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); } }
第二步，新建index.jsp和Check.jsp
index.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>My JSP 'index.jsp' starting page
Check.jsp:
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>My JSP 'index.jsp' starting page <% String checkcode=request.getParameter("checkCode"); if(checkcode.equals("")||checkcode==null){ out.print(""); }else{ if(!checkcode.equalsIgnoreCase((String)session.getAttribute("randCheckCode"))){ out.print(""); }else{ out.print("登录成功;"); } } %>
第四步：配置web.xml中的servlet，部署运行：
web.xml:
PictureCode com.servlet.PictureCode PictureCode /PictureCode index.jsp
在tomcat等服务器中部署后，打开浏览器键入：
即可查看到如图二，图三中，随机生成的验证码
