Servlet验证码

代码

package cn.itcast.web.verificationCode;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkCode")
public class CheckCodeServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int width = 100;
        int height = 50;
        //创建一对象，验证码图片对象
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

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

        //画验证码的边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width-1,height-1);

        String str="ABCDEFGHIGKLMNOPQRSTUVWXYZ0123456789";
        Random ran = new Random();

        //生成随机角标并获取字符
        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            char c = str.charAt(index);
            g.drawString(c+"",i*20,height/2);
        }


        //画线

        for (int i = 0; i < 6; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);
            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }


        //3.将图片输出到界面展示
        ImageIO.write(image,"jpg",resp.getOutputStream());


    }

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

相关类

Class BufferedImage

  包位置：
        java.lang.Object 
        java.awt.Image 
        java.awt.image.BufferedImage

//继承关系
public class BufferedImage
extends Image
implements WritableRenderedImage, Transparency

  BufferedImage类描述了一个 Image与访问图像数据缓冲区。一个 BufferedImage是由一个 ColorModel和Raster图像数据。
  在 Raster的 SampleModel数量和类型的乐队必须匹配的数量和类型的 ColorModel要求代表它的颜色和alpha分量。
  所有的 BufferedImage对象的左上角坐标（0， 0）。任何 Raster用来构建一个 BufferedImage必须有X = 0和迷你= 0。 
  这类依赖于数据的读取和Raster设置方法，并对ColorModel颜色表征方法。