tomcat6换7之后为什么在jsp页面session.setAttribute( )，后端java代码怎么都获取不到这个属性？

tomcat6换7之后为什么在jsp页面session.setAttribute( )，后端java代码怎么都获取不到这个属性？

后端代码：
package com.cdc.core.filter;

import java.io.IOException;
import java.security.interfaces.RSAPrivateKey;
import java.util.HashMap;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import com.cdc.core.util.RsaUtil;

/**

• 验证码验证过滤器及防止CSRF攻击

• @author SnoopyChen (ceo@vmeitime.com)
  *
  */
  public class CodeFilter implements Filter {

  public void destroy() {

  }

  public void doFilter(ServletRequest request, ServletResponse response,
  FilterChain chain) throws IOException, ServletException {
  HttpServletRequest req = (HttpServletRequest)request;
  HttpSession session = req.getSession();

  RSAPrivateKey privateKey = (RSAPrivateKey)session.getAttribute("privateKey");
  String random = req.getParameter("random");
  String username = req.getParameter("j_username");
  String tokenStr = req.getParameter("tokenStr");
  
  try{
      String sessionTokenStr = req.getSession().getAttribute("tokenStr").toString();
  
      String sRand = (String)session.getAttribute("rand");
  
      if( null != sRand && null!=random && sessionTokenStr.equals(RsaUtil.decryptStringByJs(privateKey, tokenStr))) {
          if(sRand.equalsIgnoreCase(RsaUtil.decryptStringByJs(privateKey,random.trim()))){
              session.removeAttribute("rand");
  
              HashMap<Object,Object> map=new HashMap(request.getParameterMap());  
              String password = request.getParameter("j_password").toString();
              password = RsaUtil.decryptStringByJs(privateKey, password);
              map.put("j_password", password);
              map.put("j_username", RsaUtil.decryptStringByJs(privateKey, username));
  

  // // System.out.println(password);

              ParameterRequestWrapper wrapRequest=new ParameterRequestWrapper(req,map);      
              chain.doFilter(wrapRequest, response);  
  

// chain.doFilter(request, response);
}else{
request.setAttribute("codeError","验证码输入不正确！");
request.setAttribute("username",RsaUtil.decryptStringByJs(privateKey, username));
//request.getRequestDispatcher("/user/login.jsp").forward(request,response);
request.getRequestDispatcher("/").forward(request,response);
}
}else{
request.getRequestDispatcher("/").forward(request,response);
}
}catch (Exception e){
e.printStackTrace();
request.setAttribute("codeError","登录失败,请重试！");
request.getRequestDispatcher("/").forward(request,response);
}

}

public void init(FilterConfig arg0) throws ServletException {

}

}

把代码贴出来