利用servlet绘制验证码

最新推荐文章于 2025-06-05 10:44:36 发布

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文章标签：

#验证码 #authCode #servlet #img

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本文介绍了一种使用Java Servlet生成包含数字和字母的图形验证码的方法。该方法通过随机选择字符并将其绘制到图片上，同时加入干扰线以提高安全性。验证码被存储在HTTP会话中以便后续验证。

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package arithmetic_web;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
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;
import javax.servlet.http.HttpSession;
/**
 * 通过servlet生成验证码
 * @author liujd
 *
 */
public class AuthCode extends HttpServlet {

	private static final long serialVersionUID = 1L;

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//告诉浏览器当做图片处理
		resp.setContentType("image/jpeg");
		//告诉浏览器不缓存
		resp.setHeader("pragma", "no-cache");
		resp.setHeader("cache-control", "no-cache");
		resp.setHeader("expires", "0");
		
		//产生由四位数字,字母构成的验证码
		int length = 4;
		String[] code = {"0","1","2","3","4","5","6","7","8","9",
						"a","b","c","d","e","f","g","h","i","j",
						"k","l","m","n","o","p","q","r","s","t",
						"u","v","w","x","y","z","A","B","C","D","E","F"
						,"F","H","I","J","K","L","M","N","O","P","Q","R","S"
						,"T","U","V","W","X","Y","Z"};
		StringBuilder authCode = new StringBuilder("");
		Random random = new Random();
		for(int i = 0 ; i<length ; i++) 
			authCode.append(code[random.nextInt(code.length)]);
		//把产生的验证码放到session里面
		HttpSession session = req.getSession();
		session.setAttribute("authCode", authCode);
		//产生图片
		int width = 70;
		int height = 20;
		BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		//获取一个Graphics(java中一个绘图类)
		Graphics g = img.getGraphics();
		//设置背景色
		g.setColor(Color.WHITE);
		//填充指定的矩形
		g.fillRect(0, 0, width, height);
		//填充干扰线
		for(int i = 0 ; i<100 ; i++) {
			  g.setColor(new Color(random.nextInt(100)+155,random.nextInt(100)+155,random.nextInt(100)+155));
			  //使用当前颜色在(x1,y1)和(x2,y2)之间画线
			  g.drawLine(random.nextInt(width), random.nextInt(height),random.nextInt(width), random.nextInt(height));
		}
		// 绘制边框
       g.setColor(Color.GRAY);
       g.drawRect(0, 0, width-1, height-1);
       // 绘制验证码(随机的字体)
       Font[] fonts = {new Font("隶书",Font.BOLD,18),new Font("楷体",Font.BOLD,18),new Font("宋体",Font.BOLD,18),new Font("幼圆",Font.BOLD,18)};
       for(int i=0; i<length; i++){
    	   //利用当前颜色，字体绘制验证码
           g.setColor(new Color(random.nextInt(150),random.nextInt(150),random.nextInt(150)));
           g.setFont(fonts[random.nextInt(fonts.length)]);
           //验证码出现位置
           g.drawString(authCode.charAt(i)+"", width/authCode.length()*i+2, 18);
       }
       // 释放此图形的上下文以及它使用的所有系统资源。
       g.dispose();
       ImageIO.write(img, "jpeg", resp.getOutputStream());
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doGet(req, resp);
	}
}