自己动手用写简单的验证码(JAVA)

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("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    private static final int WIDTH = 100;
    private static final int HEIGHT = 50;
    private static final int NUMBEROF_CODES = 4;
    private static final int NUMBEROF_LINES = 7;
    private static final int FONTSIZE = 16;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 创建图像
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_3BYTE_BGR);
        // 获取画笔对象
        Graphics pointer = image.getGraphics();
        // 填充验证码矩形图像的背景色
        pointer.setColor(Color.BLACK);
        pointer.fillRect(0, 0, WIDTH, HEIGHT);
        // 绘制边框
        pointer.setColor(Color.YELLOW);
        pointer.drawRect(0, 0, WIDTH -1, HEIGHT -1);
        // 准备待展示验证码字符集和颜色
        pointer.setColor(Color.WHITE);
        String codeSet = "ABCDEFGHIGKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        // 将验证码绘制在矩形里，并存下字符串值
        Random ran = new Random();
        int last = WIDTH / (NUMBEROF_CODES * 2);
        StringBuffer sb = new StringBuffer();
        for(int i = 0; i < NUMBEROF_CODES; i++) {
            char ch = codeSet.charAt(ran.nextInt(codeSet.length()));
            pointer.setFont(new Font("verdana", Font.BOLD, FONTSIZE));
            pointer.drawString(ch+"",
                    last = ran.nextInt(WIDTH) / NUMBEROF_CODES + last,
                    ran.nextInt((NUMBEROF_CODES - 1) * HEIGHT / NUMBEROF_CODES) + HEIGHT / NUMBEROF_CODES);
            sb.append(ch);
        }
        // 设置干扰线
        pointer.setColor(Color.PINK);
        for(int i = 0; i < NUMBEROF_LINES; i++) {
            int x1 = ran.nextInt(WIDTH), y1 = ran.nextInt(HEIGHT);
            int x2 = ran.nextInt(WIDTH), y2 = ran.nextInt(HEIGHT);
            pointer.drawLine(x1, y1, x2, y2);
        }

        // 将图片输出到页面展示
        ImageIO.write(image, "jpg", resp.getOutputStream());
    }
}

原文地址：https://www.cnblogs.com/fromneptune/p/12371546.html