java学习的第三十二天：javaweb 验证码：

package com.xiao.servlet;

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3s刷新一次：
resp.setHeader("refresh","3");

 

// 在内存中创建一张图片：
BufferedImage bufferedImage=new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
// 得到图片：
Graphics2D graphics=(Graphics2D) bufferedImage.getGraphics(); // 笔
// 设置图片的背景颜色：
graphics.setColor(Color.WHITE);
graphics.fillRect(0,0,80,20);
// 给图片写数据：

}

 

// 生成随机数：
private String makeNum{
Random random=new Random();
String num= random.nextInt(9999)+"";
StringBuffer sb=new StringBuffer();
for(int i=0;i<7-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);
}
}