使用session實現一次性驗證碼

<div id="article_content" class="article_content csdn-tracking-statistics tracking-click" data-mod="popu_519" data-dsm="post" style="overflow: hidden;"> <div class="htmledit_views">html

在登陸頁面和各類頁面，會看到有驗證碼輸入，這樣作的目的是爲了防止密碼猜想工具破解密碼，保護了用戶密碼安全，驗證碼只能使用一次，這樣就給密碼猜想工具帶來了很大的困難，基本上阻斷了密碼猜想工具的使用。        能夠使用session得到一次性驗證碼。先看一下登陸頁面，即顯示驗證碼的頁面，代碼爲： <div class="dp-highlighter bg_html"><div class="bar"><div class="tools">[html] <a href="#" class="ViewSource" title="view plain" onclick="dp.sh.Toolbar.Command('ViewSource',this);return false;">view plain</a> <a href="#" class="CopyToClipboard" title="copy" onclick="dp.sh.Toolbar.Command('CopyToClipboard',this);return false;">copy</a><div style="position: absolute; left: 498px; top: 388px; width: 16px; height: 16px; z-index: 99;"><embed id="ZeroClipboardMovie_1" src="http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf" loop="false" menu="false" quality="best" bgcolor="#ffffff" width="16" height="16" name="ZeroClipboardMovie_1" align="middle" allowscriptaccess="always" allowfullscreen="false" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" flashvars="id=1&width=16&height=16" wmode="transparent"></div> <a href="#" class="PrintSource" title="print" onclick="dp.sh.Toolbar.Command('PrintSource',this);return false;">print</a><a href="#" class="About" title="?" onclick="dp.sh.Toolbar.Command('About',this);return false;">?</a></div></div><ol start="1" class="dp-xml"><li class="alt"><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  </li><li class=""><html>  </li><li class="alt">  <head>  </li><li class="">    <title>CheckCode.html</title>  </li><li class="alt">    <meta http-equiv="content-type" content="text/html; charset=UTF-8">  </li><li class="">  </head>  </li><li class="alt">    </li><li class="">  <body>  </li><li class="alt">    <form action="/learnJS/servlet/LoginFormServlet" method="post">  </li><li class="">    用戶名：<input type="text" name="name"/><br/>  </li><li class="alt">    密     碼:<input type="password" name="pass"><br/>  </li><li class="">    驗證碼：<input type="text" name="check_code"/>  </li><li class="alt">    <img src="/learnJS/servlet/CheckCodeServlet"/><br/>  </li><li class="">   <input type="submit" name="登陸"/>   </li><li class="alt">    </form>  </li><li class="">  </body>  </li><li class="alt"></html>  </li></ol></div><pre class="html" name="code" style="display: none;"><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>CheckCode.html</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head>java

<body> <form action="/learnJS/servlet/LoginFormServlet" method="post"> 用戶名：<input type="text" name="name"/> 密碼:<input type="password" name="pass"> 驗證碼：<input type="text" name="check_code"/> <img src="/learnJS/servlet/CheckCodeServlet"/> <input type="submit" name="登陸"/> </form> </body> </html> </pre> 驗證碼存放在一張圖片上，那圖片是經過servlet產生的，在servlet中先產生驗證碼存放到session中，供之後驗證使用，而後在畫一張圖片，將驗證碼無規則的放在圖片上，在圖片上畫上干擾字符，而後就能夠啦。代碼以下：瀏覽器

<div class="dp-highlighter bg_java"><div class="bar"><div class="tools">[java] <a href="#" class="ViewSource" title="view plain" onclick="dp.sh.Toolbar.Command('ViewSource',this);return false;">view plain</a> <a href="#" class="CopyToClipboard" title="copy" onclick="dp.sh.Toolbar.Command('CopyToClipboard',this);return false;">copy</a><div style="position: absolute; left: 496px; top: 859px; width: 16px; height: 16px; z-index: 99;"><embed id="ZeroClipboardMovie_2" src="http://static.blog.csdn.net/scripts/ZeroClipboard/ZeroClipboard.swf" loop="false" menu="false" quality="best" bgcolor="#ffffff" width="16" height="16" name="ZeroClipboardMovie_2" align="middle" allowscriptaccess="always" allowfullscreen="false" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" flashvars="id=2&width=16&height=16" wmode="transparent"></div> <a href="#" class="PrintSource" title="print" onclick="dp.sh.Toolbar.Command('PrintSource',this);return false;">print</a><a href="#" class="About" title="?" onclick="dp.sh.Toolbar.Command('About',this);return false;">?</a></div></div><ol start="1" class="dp-j"><li class="alt">package com.you.servlet;  </li><li class="">  </li><li class="alt">import java.awt.Color;  </li><li class="">import java.awt.Font;  </li><li class="alt">import java.awt.Graphics;  </li><li class="">import java.awt.image.BufferedImage;  </li><li class="alt">import java.io.ByteArrayOutputStream;  </li><li class="">import java.io.IOException;  </li><li class="alt">  </li><li class="">import javax.imageio.ImageIO;  </li><li class="alt">import javax.servlet.ServletException;  </li><li class="">import javax.servlet.ServletOutputStream;  </li><li class="alt">import javax.servlet.http.HttpServlet;  </li><li class="">import javax.servlet.http.HttpServletRequest;  </li><li class="alt">import javax.servlet.http.HttpServletResponse;  </li><li class="">import javax.servlet.http.HttpSession;  </li><li class="alt">  </li><li class="">public class CheckCodeServlet extends HttpServlet {  </li><li class="alt">    private static int WIDTH = 60;  </li><li class="">    private static int HEIGHT = 20;  </li><li class="alt">  </li><li class="">    public void doGet(HttpServletRequest request, HttpServletResponse response)  </li><li class="alt">            throws ServletException, IOException {  </li><li class="">        HttpSession session = request.getSession();  </li><li class="alt">        response.setContentType("image/jpeg");  </li><li class="">        ServletOutputStream sos = response.getOutputStream();  </li><li class="alt">          </li><li class="">        //設置瀏覽器不要緩存此圖片  </li><li class="alt">        response.setHeader("Pragma", "No-cache");  </li><li class="">        response.setHeader("Cache-Control", "no-cache");  </li><li class="alt">        response.setDateHeader("Expires", 0);  </li><li class="">          </li><li class="alt">        //建立內存圖像並得到其圖形上下文  </li><li class="">        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);  </li><li class="alt">        Graphics g = image.getGraphics();  </li><li class="">          </li><li class="alt">        //產生隨機的驗證碼  </li><li class="">        char[] rands = generateCheckCode();  </li><li class="alt">          </li><li class="">        //產生圖像  </li><li class="alt">        drawBackground(g);  </li><li class="">        drawRands(g, rands);  </li><li class="alt">          </li><li class="">        //結束圖像的繪製過程，完成圖像  </li><li class="alt">        g.dispose();  </li><li class="">          </li><li class="alt">        //將圖像輸出到客戶端  </li><li class="">        ByteArrayOutputStream bos = new ByteArrayOutputStream();  </li><li class="alt">        ImageIO.write(image, "JPEG", bos);  </li><li class="">        byte[] buf = bos.toByteArray();  </li><li class="alt">        response.setContentLength(buf.length);  </li><li class="">        sos.write(buf);  </li><li class="alt">        bos.close();  </li><li class="">        sos.close();  </li><li class="alt">          </li><li class="">        //將當前驗證碼存入到session中  </li><li class="alt">        session.setAttribute("check_code", new String(rands));  </li><li class="">  </li><li class="alt">    }  </li><li class="">  </li><li class="alt">    public void doPost(HttpServletRequest request, HttpServletResponse response)  </li><li class="">            throws ServletException, IOException {  </li><li class="alt">  </li><li class="">        doGet(request, response);  </li><li class="alt">    }  </li><li class="">      </li><li class="alt">    private char[] generateCheckCode() {  </li><li class="">        //定義驗證碼的字符集  </li><li class="alt">        String chars = "0123456789abcdefghigklmnopqrstuvwxyz";  </li><li class="">        char[] rands = new char[4];  </li><li class="alt">        for(int i = 0; i < 4; i++) {  </li><li class="">            int rand = (int)(Math.random() * 36);  </li><li class="alt">            rands[i] = chars.charAt(rand);  </li><li class="">        }  </li><li class="alt">        return rands;  </li><li class="">    }  </li><li class="alt">      </li><li class="">    private void drawRands(Graphics g, char[] rands) {  </li><li class="alt">        g.setColor(Color.BLACK);  </li><li class="">        g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));  </li><li class="alt">        //在不一樣的高度上輸出驗證碼的每一個字符  </li><li class="">        g.drawString("" + rands[0], 1, 17);  </li><li class="alt">        g.drawString("" + rands[1], 16, 15);  </li><li class="">        g.drawString("" + rands[2], 31, 18);  </li><li class="alt">        g.drawString("" + rands[3], 46, 16);  </li><li class="">        System.out.println(rands);  </li><li class="alt">    }  </li><li class="">      </li><li class="alt">    private void drawBackground(Graphics g) {  </li><li class="">        //畫背景  </li><li class="alt">        g.setColor(new Color(0xDCDCDC));  </li><li class="">        g.fillRect(0, 0, WIDTH, HEIGHT);  </li><li class="alt">        //隨機產生120個干擾點   </li><li class="">        for(int i = 0; i < 120; i++) {  </li><li class="alt">            int x = (int)(Math.random() * WIDTH);  </li><li class="">            int y = (int)(Math.random() * HEIGHT);  </li><li class="alt">            int red = (int)(Math.random() * 255);  </li><li class="">            int green = (int)(Math.random() * 255);  </li><li class="alt">            int blue = (int)(Math.random() * 255);  </li><li class="">            g.setColor(new Color(red, green, blue));  </li><li class="alt">            g.drawOval(x, y, 1, 0);  </li><li class="">        }  </li><li class="alt">    }  </li><li class="">  </li><li class="alt">}  </li></ol></div><pre class="java" name="code" style="display: none;">package com.you.servlet;緩存

import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.ByteArrayOutputStream; import java.io.IOException;安全

import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;服務器

public class CheckCodeServlet extends HttpServlet { private static int WIDTH = 60; private static int HEIGHT = 20;session

public void doGet(HttpServletRequest request, HttpServletResponse response)
		throws ServletException, IOException {
	HttpSession session = request.getSession();
	response.setContentType("image/jpeg");
	ServletOutputStream sos = response.getOutputStream();
	
	//設置瀏覽器不要緩存此圖片
	response.setHeader("Pragma", "No-cache");
	response.setHeader("Cache-Control", "no-cache");
	response.setDateHeader("Expires", 0);
	
	//建立內存圖像並得到其圖形上下文
	BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
	Graphics g = image.getGraphics();
	
	//產生隨機的驗證碼
	char[] rands = generateCheckCode();
	
	//產生圖像
	drawBackground(g);
	drawRands(g, rands);
	
	//結束圖像的繪製過程，完成圖像
	g.dispose();
	
	//將圖像輸出到客戶端
	ByteArrayOutputStream bos = new ByteArrayOutputStream();
	ImageIO.write(image, "JPEG", bos);
	byte[] buf = bos.toByteArray();
	response.setContentLength(buf.length);
	sos.write(buf);
	bos.close();
	sos.close();
	
	//將當前驗證碼存入到session中
	session.setAttribute("check_code", new String(rands));

}

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

	doGet(request, response);
}

private char[] generateCheckCode() {
	//定義驗證碼的字符集
	String chars = "0123456789abcdefghigklmnopqrstuvwxyz";
	char[] rands = new char[4];
	for(int i = 0; i &lt; 4; i++) {
		int rand = (int)(Math.random() * 36);
		rands[i] = chars.charAt(rand);
	}
	return rands;
}

private void drawRands(Graphics g, char[] rands) {
	g.setColor(Color.BLACK);
	g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));
	//在不一樣的高度上輸出驗證碼的每一個字符
	g.drawString("" + rands[0], 1, 17);
	g.drawString("" + rands[1], 16, 15);
	g.drawString("" + rands[2], 31, 18);
	g.drawString("" + rands[3], 46, 16);
	System.out.println(rands);
}

private void drawBackground(Graphics g) {
	//畫背景
	g.setColor(new Color(0xDCDCDC));
	g.fillRect(0, 0, WIDTH, HEIGHT);
	//隨機產生120個干擾點 
	for(int i = 0; i &lt; 120; i++) {
		int x = (int)(Math.random() * WIDTH);
		int y = (int)(Math.random() * HEIGHT);
		int red = (int)(Math.random() * 255);
		int green = (int)(Math.random() * 255);
		int blue = (int)(Math.random() * 255);
		g.setColor(new Color(red, green, blue));
		g.drawOval(x, y, 1, 0);
	}
}

} </pre> 而後是登陸以後處理用戶是否登陸成功的servlet，在這個servlet中經過比較session中存放的驗證碼和用戶輸入的驗證碼，若是匹配則進行下一步判斷，若是不匹配直接輸出驗證碼不匹配的問題。代碼爲：app

import java.io.IOException; import java.io.PrintWriter;工具

import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;

public class LoginFormServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
		throws ServletException, IOException {
	response.setContentType("text/html;charset=utf-8");
	PrintWriter out = response.getWriter();
	
	HttpSession session = request.getSession(false);
	if(session == null) {
		out.print("驗證碼處理問題");
		return;
	}
	
	String saveCode = (String)session.getAttribute("check_code");
	if(saveCode == null) {
		out.print("驗證碼處理問題");
		return;
	}
	
	String checkCode = request.getParameter("check_code");
	if(!saveCode.equals(checkCode)) {
		out.print("驗證碼無效!");
		return;
	}
	
	session.removeAttribute("check_code");
	out.print("驗證碼經過，服務器正在校驗用戶名和密碼！");

}

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

	doGet(request, response);
}

} </pre> </div> </div>