java生成验证码的源代码

package com.jun.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class ImageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//如何让浏览器三秒自动刷新一次
resp.setHeader(“refresh”,“3”);
//在内存中创建一个图片
BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
//得到图片
Graphics2D g = (Graphics2D)image.getGraphics();
//设置图片背景颜色
g.setColor(Color.white);
g.fillRect(0,0,80,20);
//给图片写数据
g.setColor(Color.blue);
g.setFont(new Font(null,Font.BOLD,20));
g.drawString(makeNum(),0,20);
//告诉浏览器，这个请求用图片的方式打开
resp.setContentType(“image/jpeg”);
//网站存在缓存，不让浏览器缓存
resp.setDateHeader(“expires”,-1);
resp.setHeader(“Cache-Control”,“no-cache”);
resp.setHeader(“Pragma”,“no-cache”);
//把图片写给浏览器
ImageIO.write(image,“jpg”,resp.getOutputStream());

}

//生成随机数
private String makeNum() {
Random random=new Random();
String num=random.nextInt(999999)+“”;
StringBuffer sb=new StringBuffer();
for (int i = 0; i < 6-num.length(); i++) {
sb.append(“0”);
}
num=sb.toString()+num;
return num;
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    doGet(req, resp);
}

}