servlet过滤器中取值问题？

Question

public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
  
  HttpServletRequest req = (HttpServletRequest) arg0;
  HttpSession session = ((HttpServletRequest)arg0).getSession();
    if(session.getAttribute("backSubmit")!=null){
     String backSubmit=session.getAttribute("backSubmit").toString();
       String nowSubmit=req.getParameter("secondSubmitFlag");
       if(backSubmit.equals(nowSubmit)){
       ((HttpServletResponse)arg1). sendRedirect(((HttpServletRequest)arg0).getContextPath()+"/hello.jsp");
       }else{
       session.setAttribute("backSubmit", nowSubmit); 
       }
    
    }else{
        String backSubmit=req.getParameter("secondSubmitFlag");
                          //此时为null
        session.setAttribute("backSubmit", backSubmit);
    }
         
          
  arg2.doFilter(arg0, arg1);  }
请问为什么我取不到secondSubmitFlag这个值呢？<input type="hidden" name="secondSubmitFlag" value="value1">

Answer 1

req.getRequestURI()；
看看你请求的路径是否被filter过滤啦

Answer 2

 String aa=req.getRequestURI() 
 我这样获取了
 为什么输出如下内容呢？为什么不是url啊？
------------/QIS/css/operationdata.css
11:05:39,843 INFO  [STDOUT] ------------/QIS/css/data.css
11:05:39,875 INFO  [STDOUT] ------------/QIS/js/pagelist.js
11:05:39,890 INFO  [STDOUT] ------------/QIS/js/tbindex.js
11:05:39,906 INFO  [STDOUT] ------------/QIS/js/operationData.js
11:05:39,906 INFO  [STDOUT] ------------/QIS/js/refer.js
11:05:39,953 INFO  [STDOUT] ------------/QIS/js/prototype.js
11:05:39,968 INFO  [STDOUT] ------------/QIS/js/tooltips.js
11:05:40,125 INFO  [STDOUT] ------------/QIS/js/effects.js
11:05:40,156 INFO  [STDOUT] ------------/QIS/js/validation_cn.js
11:05:40,171 INFO  [STDOUT] ------------/QIS/css/style_min.css
11:05:40,171 INFO  [STDOUT] ------------/QIS/js/focus.js

Answer 3

String aa=req.getRequestURI() 
第一条是你请求的action的path,也就是 *.do 是你工程名后面的 以后的是些什么JS，CSS，