jsp中生成的验证码和存在session里面的验证码不一致的处理

╰半橙微兮° 2024-02-17 14:20 32阅读 0赞

今天在调试项目的时候发现，在提交表单的时候的验证码有问题，问题是这样的：就是通过debug模式查看得知：jsp页面生成的验证码和表单输入的页面输入的一样，但是到后台执行的时候，你会发现他们是不一样的，现在上图看看：

1.这是表单提交的时候:

![SouthEast][]

2.这是后台得到的生成的验证码：

![SouthEast 1][]

3.这是后台得到输入的验证码：

![SouthEast 2][]

这样的问题还是头一次出现，以前没遇到过，经过google，baidu，最后得知是这样的：因为加载jsp页面比加载session快一些

那怎么办才能解决这个办法呢，

又经过多次搜索，思考，实践，终于想出了个好办法

1.在jsp页面用js生成验证码并保存在变量中，验证码作为参数传到java(继承了HttpServlet)类

2.根据jsp页面中传过来的验证码画出一个有干扰线或干扰点的图片

3.在WEB-INF/web.xml中配置 servlet

4.在jsp页面调用配置好的servlet，一般是通过<img src="servlet名" id="code"/>调用

5.提交数据之前验证

局部刷新验证码：<a href="\#" οnclick="javascript:show();return false;">看不清,换一张！</a>-----return false;很重要啊

下面直接附上我的例子：

截图如下：

![SouthEast 3][]

代码如下：

1.JAVA类：CodeServlet.java:

package cn.gov.csrc.servlet;
    
    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.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.sun.image.codec.jpeg.JPEGCodec;
    import com.sun.image.codec.jpeg.JPEGImageEncoder;
    
    public class CodeServlet extends HttpServlet {
    
    	/**
    	 * 产生验证码图片
    	 */
    	public void doGet(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    		response.setContentType("image/jpeg");
    		response.setHeader("Cache-Control", "no-cache");
    		response.setHeader("Pragma", "No-cache");
    		response.setDateHeader("Expires", 0L);
    		int width = 80;
    		int height = 30;
    		BufferedImage image = new BufferedImage(width, height, 1);
    		Graphics g = image.getGraphics();
    		Random random = new Random();
    		g.setColor(getRandColor(200, 250));
    		g.fillRect(0, 0, width, height);
    		g.setFont(new Font("Arial", 0, 25));
    		g.setColor(getRandColor(160, 200));
    		for (int i = 0; i < 155; i++) {
    			int x = random.nextInt(width + 100);
    			int y = random.nextInt(height + 100);
    			int xl = random.nextInt(10);
    			int yl = random.nextInt(12);
    			g.drawOval(x, y, x + xl, y + yl);
    		}
    		String code = request.getParameter("code");
    		String sRand = code;
    		for (int i = 0; i < sRand.length(); i++) {
    			String rand = sRand.substring(i, i + 1);
    			g.setColor(new Color(20 + random.nextInt(110), 20 + random
    					.nextInt(110), 20 + random.nextInt(110)));
    			g.drawString(rand, 14 * i + 5, 25);
    		}
    		g.dispose();
    		javax.servlet.ServletOutputStream imageOut = response.getOutputStream();
    		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(imageOut);
    		encoder.encode(image);
    	}
    
    	private 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);
    	}
    
    }

2.Web.xml文件：

<?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">
    	<display-name></display-name>
    	<welcome-file-list>
    		<welcome-file>index.jsp</welcome-file>
    	</welcome-file-list>
    	<servlet>
    		<servlet-name>CodeServlet</servlet-name>
    		<servlet-class>cn.gov.csrc.servlet.CodeServlet</servlet-class>
    	</servlet>
    	<servlet-mapping>
    		<servlet-name>CodeServlet</servlet-name>
    		<url-pattern>/CodeServlet</url-pattern>
    	</servlet-mapping>
    </web-app>

3.index.jsp：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <%
    	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>验证码测试</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">
    <script language="javascript" type="text/javascript">
    var code ; //在全局 定义验证码 
    function createCode(){  
        code = "";  
        var codeLength = 5;//验证码的长度  
        //所有候选组成验证码的字符，可以用中文  
        var selectChar = new Array(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','g','h','i','j','k','l','m','n','o','p',
        		'q','r','s','t','u','v','w','x','y','z');  
        for(var i=0;i<codeLength;i++){  
            var charIndex = Math.floor(Math.random()*60);  
            code +=selectChar[charIndex];  
        }  
        return code;  
    }  
    function validate (){  
        var inputCode = document.getElementById("vcode").value.toLowerCase();  
        if(inputCode.length <=0){  
            alert("请输入验证码！");  
            return false;  
        }  
        else if(inputCode != code.toLowerCase()){  
            alert("验证码输入错误！");  
            show();//刷新验证码  
            return false;  
        }else{  
            alert("^-^ OK");  
            return true;  
        }  
    }  
    function show(){  
            //显示验证码  
            document.getElementById("code").src="CodeServlet?code="+createCode();  
    }  
    window.onload = function() {
    		//document.οnlοad=show();  
            show();//页面加载时加载验证码  
            //这时无论在ie还是在firefox中，js没有加载完，页面的东西是不会被执行的；  
        }  
    </script>
    </head>
    
    <body>
    	<form οnsubmit="return validate();" action="" method="post">
    		<h3>jsp+js+servlet实现验证码</h3>
    		<br /> 用户名：<input type="text" name="" /><br /> 请输入验证码： <input
    			type="text" id="vcode" style="width: 60;" maxLength="5" /> <img
    			src="" id="code" /> <a href="#" mce_href="#"
    			οnclick="javascript:show();return false;">看不清,换一张!</a><br /> <input
    			type="submit" />
    	</form>
    </body>
    </html>

下载代码请访问：http://www.zuidaima.com/share/1720368578202624.htm

[SouthEast]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/590244fe8514431baf784918c3a7a7ef.png
[SouthEast 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/3617552e29e74a8db7b3255b0aa1a2c2.png
[SouthEast 2]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/f701ca70821b4597a381ec34db8500dd.png
[SouthEast 3]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/ae9f9efe93db4fb38e6283a285710fe1.png