生成一个简单的javaweb验证码

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互联网集市收集整理的这篇技术教程文章主要介绍了生成一个简单的javaweb验证码，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含1722字，纯文字阅读大概需要3分钟。

内容图文

只是生成一个验证码图片

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 {
        //Set the browser refresh time
        resp.setHeader("refresh","4");
        //Set image size
        BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
        //Make a brush
        Graphics g = image.getGraphics();
        //Set the brush color
        g.setColor(Color.white);
        //The background of the fill image is white
        g.fillRect(0,0,80,20);
        //Set the brush color to pink
        g.setColor(Color.pink);
        g.setFont(new Font("null",Font.BOLD,20));
        //Draw a seven-digit number
        g.drawString(makeNum(),0,20);
        //Set the browser's content type to image
        resp.setContentType("image/jpg");
        //Disable browser caching
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");
        //Displays images to the client
        ImageIO.write(image,"jpg",resp.getOutputStream());
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    private String makeNum(){
        Random r = new Random();
        //Pseudorandom generates a seven-digit number
        String num = String.valueOf(r.nextInt(9999999));
        StringBuilder s = new StringBuilder();
        //If there are fewer than seven digits, add a 0 in front of it.
        for (int i = 0; i < 7-num.length(); i++){
            s.append("0");
        }
        num = s.toString()+num;
        return num;
    }
}

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