jsp中生成的验证码和存在session里面的验证码不一致的处理

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:



2.这是后台得到的生成的验证码：



3.这是后台得到输入的验证码：



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

<form onsubmit="return validate();"……/>

局部刷新验证码：<a href="#" onclick="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：



代码如下：

1.JAVA类：CodeServlet.java:

[java] view plain copy print?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);
}

}

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：

[html] view plain copy print?<?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>

<?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：

[javascript] view plain copy print?<%@ 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.onload=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 onsubmit="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="#"
onclick="javascript:show();return false;">看不清,换一张!</a><br /> <input
type="submit" />
</form>
</body>
</html>

<%@ 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.onload=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 onsubmit="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="#"            onclick="javascript:show();return false;">看不清,换一张!</a><br /> <input            type="submit" />    </form></body></html>