Response_验证码_分析以及代码实现

Response_验证码_分析以及代码实现

本质：图片

目的：防止恶意表单注册

步骤：

　　1.创建对象，在内存中图片（验证码图片对象）

　　2.美化图片

　　3.将图片输出到页面展示

package com.example.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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;

@WebServlet(name = "ResponseDemo5", value = "/ResponseDemo5")
public class ResponseDemo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        int width = 100;// 高
        int height = 50;// 宽

        //1.创建一对象，在内存中图片
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

        //2.美化图片
        //2.1填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0, 0, width, height);

        //2.2画边框
        g.setColor(Color.BLACK);
        g.drawRect(0, 0, width - 1, height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();

        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            //2.3验证码
            g.drawString(ch+"", width/5*i, height/2);
        }

        //2.4画干扰线
        g.setColor(Color.GREEN);
        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);

            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1, x2, y1, y2);
        }
        
        //3.将图片输出到页面展示
        ImageIO.write(image, "jpg", response.getOutputStream());
    }
}