package com.gen;

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 imageController extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //设置浏览器三秒刷新一次

        resp.setHeader("refresh", "3");

        //在内存中创建一个图片

        BufferedImage bufferedImage = new BufferedImage(100, 30, BufferedImage.TYPE_INT_RGB);

        //获取图片

        Graphics2D graphics = (Graphics2D) bufferedImage.getGraphics();

        //设置背景颜色

        graphics.setColor(Color.white);

        //设置字体

        graphics.setFont(new Font(null,Font.BOLD,30));

        graphics.drawString(makenum(), 0, 30);

        //指定浏览器要打开的方式

        resp.setContentType("image/jpeg");

        //设置浏览器无缓存

        resp.setDateHeader("expires",-1);

        resp.setHeader("Cache-control","no-cache");

        resp.setHeader("Pragma","no-cache");

        //输出客户端

        ImageIO.write(bufferedImage,"jpg",resp.getOutputStream());

    }

    private String makenum() {

        int num = new Random().nextInt(9999);

        StringBuffer sb = new StringBuffer();

        for (int j = 0; j < 4.; j++) {

            sb.append("0");

        }

        return sb.toString() + num;

    }

    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        doGet(req, resp);

    }

}