Servlet中Response对象应用2(输出随机验证码图片)

预期结果如图：

可用于登陆界面的验证

需要使用random类和绘画相关的几个类。以及imageio的内容。

import java.awt.*;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Random;

import javax.imageio.ImageIO;

//1、创建一个内存图像，并设置长和高BufferedImage

//2、得到该图像 的画笔Graphics

//2.1画边框

//2.2画背景色

//2.3画干扰线9条

//2.4画验证数字4个数字

//3、输出response的输出流中ImageIO

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下面是源码

package com.response;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet4 extends HttpServlet {
    private static int WIDTH = 120;
    private static int HEIGHT = 25;
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //不要缓存
        response.setHeader("Expires", "-1");
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        //1、创建一个内存图像，并设置长和高BufferedImage
        BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
        //2、得到该图像 的画笔Graphics
        Graphics g = image.getGraphics();
            //2.1画边框
            g.setColor(Color.BLUE);
            g.drawRect(0, 0, WIDTH, HEIGHT);
            //2.2画背景色
            g.setColor(Color.GRAY);
            g.fillRect(1, 1, WIDTH-2, HEIGHT-2);
            //2.3画干扰线9条
            g.setColor(Color.YELLOW);
            Random r = new Random();
            for(int i=0;i<9;i++){
                g.drawLine(r.nextInt(WIDTH), r.nextInt(HEIGHT), r.nextInt(WIDTH), r.nextInt(HEIGHT));
            }
            //2.4画验证数字4个数字
            g.setColor(Color.RED);
            g.setFont(new Font("宋体",Font.BOLD,20));
            int x = 5;
            for(int i=0;i<4;i++){
                g.drawString(r.nextInt(9)+"", x, 20);
                x+=30;
            }
        //3、输出response的输出流中ImageIO
        ImageIO.write(image, "jpeg", response.getOutputStream());
        System.out.println("有浏览器请求了验证码");

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        out.flush();
        out.close();
    }

}