java - httprequest.getsession 返回 null

Question

我编写了一个过滤器，它会使当前 session 无效并创建新 session 并将旧 session 的属性复制到新 session 中。这在 tomcat5 和 jdk 1,4 中工作正常但是当我将它切换到 tomcat6 和 jdk 1.6 时过滤器运行后，下一个请求 httprequest.getsession(false ) 为 null。为什么它在 tomcat 6 中表现不同。请帮忙。这是代码片段

public void doFilter(ServletRequest request, ServletResponse response,
                        FilterChain chain) throws IOException, ServletException 
                        { 
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        System.out.println("within GenerteNewSessionFilter");
        System.out.println("within GenerteNewSessionFilter getRequestURI"+httpRequest.getRequestURI());
        System.out.println("within GenerteNewSessionFilter getRequestURL"+httpRequest.getRequestURL());

        System.out.println("within GenerteNewSessionFilter session false"+httpRequest.getSession(false));

        String reqUrl=httpRequest.getRequestURL().toString();
        if (reqUrl==null){
            reqUrl="";
        }
        int idxLogin=reqUrl.indexOf("LoginSubmit.jsp");
        int idxReg=reqUrl.indexOf("RegistrationSubmit.jsp");
        int idxErr=reqUrl.indexOf("Error");

    int idxSave=-1;
    System.out.println("within GenerteNewSessionFilter reqUrl "+reqUrl);
    System.out.println("within GenerteNewSessionFilter idxLogin index"+idxLogin);
    System.out.println("within GenerteNewSessionFilter idxReg index"+idxReg);
    System.out.println("within GenerteNewSessionFilter idxErr index"+idxErr);

    if (httpRequest.getSession(false) != null  &&  (idxLogin >0 || idxReg >0) && idxErr <0 ){
      //copy session attributes from old session to a map. 
        System.out.println("copy session attributes from old session to a map");
        HttpSession session = httpRequest.getSession();

      HashMap old=new HashMap();
      Enumeration keys = (Enumeration) session.getAttributeNames();
      while (keys.hasMoreElements()) {
        String key = (String) keys.nextElement();

       old.put(key, session.getAttribute(key));
          session.removeAttribute(key);


      }
      System.out.println("old  session id  "+session.getId());

      //invalidate session and create new session.
      session.invalidate();
      //create new session
      session = httpRequest.getSession(true);

      //copy session attributes from map session to new session
      Iterator it = old.entrySet().iterator(); //iterator
      while (it.hasNext()) {
          Map.Entry pairs = (Map.Entry)it.next();
          //putitng old attributes in to new session
          session.setAttribute((String) pairs.getKey(), pairs.getValue());

      }//end while loop
          System.out.println("end copy  session attributes");
          System.out.println("new session id status "+httpRequest.getSession(false));
          System.out.println("final new   session session id  "+session.getId());
    }
    chain.doFilter(request, response);
    }
      public void init(FilterConfig filterConfig) throws ServletException {


    }

}         

Answer 1

HttpServletRequest.getSession(boolean create) 的 javadoc明确指出，如果您将 false 值传递给它的参数，它只会返回 HttpSession(如果已经存在)。如果没有与请求关联的 session ，它将返回 null。

因此，如果您使当前 session 无效，显然在您的下一个请求中调用 request.getSession(false) 将返回 null。

如果您想在使当前 session 无效后创建一个新 session ，请使用:request.getSession(true) 或更简单:request.getSession()。