servlet实现无刷新页面更换验证码

最新推荐文章于 2019-08-21 16:36:44 发布

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#servlet #random #import #string #stylesheet #session

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本文详细介绍了如何使用Java生成动态验证码，并将其应用于HTTP请求处理。通过设置字体、颜色和干扰线，确保了验证码的不可预测性和安全性。此外，文章还展示了如何将生成的验证码存储在session中，以便于客户端进行验证。

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index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://"
			+ request.getServerName() + ":" + request.getServerPort()
			+ path + "/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
	<head>
		<base href="<%=basePath%>">

		<title>My JSP 'index.jsp' starting page</title>
		<meta http-equiv="pragma" content="no-cache">
		<meta http-equiv="cache-control" content="no-cache">
		<meta http-equiv="expires" content="0">
		<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
		<meta http-equiv="description" content="This is my page">
		<!--   
    <link rel="stylesheet" type="text/css" href="styles.css">   
    -->
		<script>
function refresh() {
	document.getElementById("authImg").src = 'servlet/check?now=' + new Date();
}
</script>
	</head>

	<body>
		<form>
			<input type="text" name="d">
		</form>
		验证码如图：
		<img src="servlet/check" id="authImg" />
		
		<a href="#" onClick="refresh()">看不清？</a>
	</body>
</html>

servlet

package com.zljy.test;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;
/**
 * @author zcshun
 * @see 
 * @date 2012-7-6 上午11:02:07
 */
public class check extends HttpServlet {
	
	//设置验证码字符的字体和字号。
	private Font mFont = new Font("Arial Black", Font.PLAIN, 16);

	public void init() throws ServletException {
		super.init();
	}

	Color getRandColor(int fc, int bc) {
		Random random = new Random();
		if (fc > 255)
			fc = 255;
		if (bc > 255)
			bc = 255;
		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);
		return new Color(r, g, b);
	}

	public void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		response.setContentType("image/jpeg");

		//设置验证码图片的长度和高度。
		int width = 100, height = 23;
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);

		Graphics g = image.getGraphics();
		Random random = new Random();
		g.setColor(getRandColor(200, 250));
		g.fillRect(1, 1, width - 1, height - 1);
		g.setColor(new Color(102, 102, 102));
		g.drawRect(0, 0, width - 1, height - 1);
		g.setFont(mFont);

		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 155; i++) {
			int x = random.nextInt(width - 1);
			int y = random.nextInt(height - 1);
			int xl = random.nextInt(6) + 1;
			int yl = random.nextInt(12) + 1;
			g.drawLine(x, y, x + xl, y + yl);
		}
		for (int i = 0; i < 70; i++) {
			int x = random.nextInt(width - 1);
			int y = random.nextInt(height - 1);
			int xl = random.nextInt(12) + 1;
			int yl = random.nextInt(6) + 1;
			g.drawLine(x, y, x - xl, y - yl);
		}

		String sRand = "";
		//设置验证码字符串的长度。当前为6个。
		for (int i = 0; i < 6; i++) {
			String tmp = getRandomChar();
			sRand += tmp;
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			g.drawString(tmp, 15 * i + 10, 15);
		}

		HttpSession session = request.getSession(true);
		// 把验证码防到session中，用来前台对比。
		session.setAttribute("rand", sRand);
		g.dispose();
		ImageIO.write(image, "JPEG", response.getOutputStream());
	}

	private String getRandomChar() {
		int rand = (int) Math.round(Math.random() * 2);
		long itmp = 0;
		char ctmp = '\u0000';
		switch (rand) {
		case 1:
			itmp = Math.round(Math.random() * 25 + 65);
			ctmp = (char) itmp;
			return String.valueOf(ctmp);
		case 2:
			itmp = Math.round(Math.random() * 25 + 97);
			ctmp = (char) itmp;
			return String.valueOf(ctmp);
		default:
			itmp = Math.round(Math.random() * 9);
			return String.valueOf(itmp);
		}
	}
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>check</servlet-name>
    <servlet-class>com.zljy.test.check</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>check</servlet-name>
    <url-pattern>/servlet/check</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>