基于Servlet的验证码Demo

package com.aloha.identifyingcode;

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;

public class IdentifyingCode extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//告诉所有品牌客户端不使用缓存
		response.setHeader("pragma", "no-cache");
		response.setHeader("cache-control", "no-cache");
		response.setHeader("expires", "0");
		
		int width = 110;
		int height = 25;
		//在内存中创建一个图像
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		//获取图像
		Graphics g = image.getGraphics();
		//设置验证码块的底色为粉色~
		g.setColor(Color.PINK);
		g.fillRect(1, 1, width-2, height-2);
		//设置验证码块的边框为红色~
		g.setColor(Color.RED);
		g.drawRect(0, 0, width-1, height-1);
		//设置文本格式
		g.setColor(Color.BLUE);
		g.setFont(new Font("宋体", Font.BOLD|Font.ITALIC, 15));
		//给图片添加文本
		Random random = new Random();
		int position = 20;
		for (int i = 0; i < 4; i++) {
			g.drawString(random.nextInt(10)+"", position , 20);
			position += 20;
		}
		//给图片加上9条干扰线
		for (int i = 0; i < 9; i++) {
			g.drawLine(random.nextInt(width), random.nextInt(height), random.nextInt(width), random.nextInt(height));
		}
		//图片以流的形式输出到客户端
		ImageIO.write(image, "jpg", response.getOutputStream());
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>验证码</title>
<script type="text/javascript">
	function changeCode(){
		var image = document.getElementsByTagName("img")[0];
		image.src="/identifying_code/servlet/identifyingcode?time="+new Date().getTime();
	}
</script>
</head>
<body>
	<form action="#" method="post">
	用户名：<input type="text" name="userName" /><br/>
	密&nbsp;&nbsp;&nbsp;&nbsp;码：<input type="password" name="pwd" /><br />
	验证码：<input type="text" name="code" />
	<img src="/identifying_code/servlet/identifyingcode" onclick="changeCode()"><a href="javascript:changeCode()">看不清换一张</a><br />
	<input type="submit" name="登录">
	</form>
</body>
</html>

当然，变相对象我们可以导入别人做好的jar包直接用~

基于Servlet的验证码Demo

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