request.getAttribute is null when I call it in jsp
<p>It calls Servlet by click a href.</p>

<pre><code>    &lt;li &gt;&lt;a href="&lt;%=request.getContextPath() %&gt;/ProviderServlet"&gt;privilegeManagement&lt;/a&gt;&lt;/li&gt;
</code></pre>

<p>this code is include in the navigation.jsp which is included in the main.jsp.</p>

<p>then it's my servlet.</p>

<pre><code>@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    // TODO Auto-generated method stub
    ProviderDao pd  = new ProviderDao();
    List&lt;ProviderArchives&gt; list = pd.getArchives();
    String str = "chenfeng";
    req.setAttribute("list", list);
    req.setAttribute("hu" , str);
    getServletContext().getRequestDispatcher("/jsp/main.jsp").forward(req,resp);
}
</code></pre>

<p>then it's my main.jsp.</p>

<pre><code>    &lt;%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%&gt;
&lt;%@page import="java.util.*"%&gt;
&lt;%@page import="com.chenfeng.javabean.ProviderArchives"%&gt;
&lt;%@ taglib prefix="c"    uri="http://java.sun.com/jsp/jstl/core" %&gt;
&lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"&gt;
&lt;html&gt;
&lt;head&gt;
&lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8"&gt;
&lt;title&gt;main&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
    &lt;%@ include file="navigation.jsp"%&gt;
    &lt;div&gt;
        &lt;%@ include file="management.jsp"%&gt;
    &lt;/div&gt;
    &lt;div&gt;
      &lt;%
             String k = (String)request.getAttribute("hu");
             out.println(k);
      %&gt;
       &lt;c:forEach items="${list}"  var="item"&gt;
       &lt;tr&gt; 
        &lt;td&gt;${item.provideID() }&lt;/td&gt; 
        &lt;td&gt;${item.GID }&lt;/td&gt; 
        &lt;td&gt;${item.Gname }&lt;/td&gt; 
        &lt;td&gt;${item.PID }&lt;/td&gt; 
        &lt;td&gt;${item.TEL }&lt;/td&gt; 
        &lt;td&gt;${item.ADDR }&lt;/td&gt;
        &lt;td&gt; 
         &lt;a href="QueryUserByIdServlet?id=${item.provideID }"&gt;Modify&lt;/a&gt; 
         &lt;a href="DeleteUserServlet?id=${item.provideID }"&gt;Delete&lt;/a&gt; 
        &lt;/td&gt; 
       &lt;/tr&gt; 
      &lt;/c:forEach&gt; 
    &lt;/div&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>then when I run this on server,it shows like this
<a href="https://i.stack.imgur.com/H1v3E.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/H1v3E.png" alt="result"></a>
thank in advance for any help!</p>