验证码

package com.lovo.service;

import java.awt.*;
import java.awt.image.*;

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;
import com.sun.image.codec.jpeg.*;

public class CheckCodeService extends BaseService{
 

 @Override
 public String press() {

//  设置内容类型为图片
  response.setContentType("image/jpeg");
  
  //设置客户端不加图片缓存
  response.setHeader("Pragma","No-cache");

        response.setHeader("Cache-Control","no-cache");

        response.setDateHeader("Expires", 0);
  
  //创建一个内存图片
  BufferedImage img = new BufferedImage(100,20,
    BufferedImage.TYPE_INT_RGB);
  
  //获得画笔
  Graphics g = img.getGraphics();
  
  //创建StringBuffer对象
  StringBuffer sb = new StringBuffer();
  
  for(int i=0;i<4;i++){
  //获得0-10的随机整数
   int temp = (int)(Math.random()*10);
   sb.append(temp+"   ");
  }
  
  HttpSession session = request.getSession();
  //去掉字符串
  session.setAttribute("check", sb.toString().replaceAll(" ", ""));
  
  //设置画笔颜色
  g.setColor(new Color(167,178,23));
  //绘制矩形的背景
  g.fillRect(0,0,200,30);
  
  //设置字体颜色
  g.setColor(new Color(0,0,0));
  //向画布绘制字符串
  g.drawString(sb.toString(),20,15);
  
  //得到输出字节流
  ServletOutputStream out ;
  try {
   out = response.getOutputStream();
//   发送图片数据
   JPEGImageEncoder jpg =JPEGCodec.createJPEGEncoder(out);
   jpg.encode(img);
  } catch (IOException e) {
   // TODO 自动生成 catch 块
   e.printStackTrace();
  }
  
  return null;
 }
}