验证码（Java实现）

 

package book.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
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;

public class ImageCodeMakerServlet extends HttpServlet {

 private static final long serialVersionUID = 1L;

 public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
  doPost(request,response);
 }
 public void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
  //首先设置页面不缓存
  response.setHeader("Pargma","No-cache");
  response.setHeader("Cache-Control","no-cache");
  response.setDateHeader("Expires",0);
  
  //定义图片的宽度和高度
  int width=90;
  int height=40;
  //创建一个图片对象
  BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
  //得到图象的环境对象
  Graphics g=image.createGraphics();
  Random random=new Random();
  //用随机颜色填充图象背景
  g.setColor(getRandColor(180,250));
  g.fillRect(0,0,width,height);
  for(int i=0;i<5;i++){
   g.setColor(getRandColor(50,100));
   int x=random.nextInt(width);
   int y=random.nextInt(height);
   g.drawOval(x,y,4,4);
  }
  g.setFont(new Font("",Font.PLAIN,40));//设置字体，下面准备随机数
  String sRand="";
  for(int i=0;i<4;i++){
   String rand=String.valueOf(random.nextInt(10));
   sRand+=rand;
   //生成随机颜色
   g.setColor(new Color(20+random.nextInt(80),20+random.nextInt(100),20+random.nextInt(90)));
   g.drawString(rand,(17+random.nextInt(3))*i+8,34);
   for(int k=0;k<12;k++){
    int x=random.nextInt(width);
    int y=random.nextInt(height);
    int x1=random.nextInt(9);
    int y1=random.nextInt(9);
    g.drawLine(x,y,x+x1,y+y1);
   }
  }
  request.getSession().setAttribute("randcode",sRand);
  g.dispose();
  ImageIO.write(image,"JPEG",response.getOutputStream());//输出图象到页面
 }
 public 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);
 }
}