JavaWeb11（Response验证码实现）

Response验证码实现

1.编写ImageServlet

package com.hao.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 {
    
    
        //让浏览器五秒刷新一次
        resp.setHeader("refresh","5");
        //在内存中创建一个图片
        BufferedImage bufferedImage = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
        //得到图片
        //创建画笔
        Graphics2D graphics2D = (Graphics2D)bufferedImage.getGraphics();
        //设置图片的背景颜色
        graphics2D.setColor(Color.white);
        graphics2D.fillRect(0,0,80,20);

        //写随机数
        graphics2D.setColor(Color.BLUE);
        //设置字体样式
        graphics2D.setFont(new Font("宋体",Font.BOLD,20));
        graphics2D.drawString(Randomnum(),0,20);

        //告诉浏览器以图片的形式打开请求
        resp.setContentType("image/png");
        //不让浏览器缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragme","no-cache");
        //把图片写进浏览器
        ImageIO.write(bufferedImage,"png",resp.getOutputStream());
    }
    private String Randomnum(){
    
    
        Random random = new Random();
        String str =random.nextInt(99999)+"";
        StringBuffer stringBuffer = new StringBuffer();
        //随机数不足五位时自动补0
        for (int i = 0; i <5-str.length() ; i++) {
    
    
            stringBuffer.append("0");
        }
        str = stringBuffer.toString()+str;
        return str;
    }

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

2.编写映射

<servlet>
        <servlet-name>response_image</servlet-name>
        <servlet-class>com.hao.servlet.ImageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>response_image</servlet-name>
        <url-pattern>/image</url-pattern>
    </servlet-mapping>

3.测试访问

验证码每五秒刷新一次