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" />调用

5.提交数据之前验证

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

局部刷新验证码：<a href="#" >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:

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); ???}}