package util;
import java.util.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.sun.image.codec.jpeg.*;   /** 生成验证码图片*/
public class ValidateCode extends HttpServlet
{  private Font imgFont=new Font("宋体",Font.BOLD,16);//设置字体   public void doPost(HttpServletRequest request,HttpServletResponse response)   throws ServletException,IOException   {   doGet(request,response);   }   //设置浏览器不要缓存此图片response.setHeader("Pragma","No-cache");response.setHeader("Cache-Control","no-cache");response.setDateHeader("Expires", 0);/* * 在给定范围内获得随机颜色 */ private 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); }/public void doGet(HttpServletRequest request,HttpServletResponse response)     throws ServletException,IOException   {   String strCode  ="";   //验证码(字符串形式)int intCode  =0;     //验证码(数字形式)Random random = new Random();//随机类//生成随机四位数字intCode = (new Random()).nextInt(9999);   if(intCode<1000){intCode+=1000;  }//将数字转化为字符串strCode=intCode+"";   /** 绘图*/response.setContentType("image/gif");   //获得servlet输出流ServletOutputStream servletOutputStream =response.getOutputStream();  //创建表示图像的对象(参数是：宽、高、图片类型)BufferedImage image=new BufferedImage(60,25,BufferedImage.TYPE_INT_RGB); //创建表示图形上下文的对象   Graphics graph=image.getGraphics();//设置此图形上下文的颜色graph.setColor(Color.blue);   //设定矩形的横、纵坐标，及宽、高graph.fillRect(1,1,48,18);   //将此图形上下文的字体设置为指定字体(参数为Font类型)graph.setFont(imgFont);   //随机产生10条干扰线，使图象中的认证码不易被其它程序探测到 graph.setColor(getRandColor(160,200)); for (int i=0;i<10;i++) {           int x = random.nextInt(85); int y = random.nextInt(20); int xl = random.nextInt(12); int yl = random.nextInt(12); //在此图形上下文的坐标系统中，使用当前颜色在点 (x,y) 和 (x1,y1) 之间画一条线graph.drawLine(x,y,x+xl,y+yl); } //分解验证码字符串char c;   for(int i=0;i<4;i++)   {   //返回验证码字符串指定索引处的char值(单个数字)c=strCode.charAt(i);   //使用此图形上下文的当前字体和颜色绘制由指定 string 给定的文本(x->文本的横坐标，y->文本的纵坐标)graph.drawString(c+"",9*i+4,16);     }   //对servlet输出流进行JPEG格式编码JPEGImageEncoder imageEncoder=JPEGCodec.createJPEGEncoder(servletOutputStream);   imageEncoder.encode(image);   //将获得的验证码字符串存入sessionHttpSession  session=request.getSession(true);   session.removeAttribute("VerifyCode");   session.setAttribute("VerifyCode",strCode);   //关闭输出流servletOutputStream.close();   }   }