title: Jsp cache problem
body: <p>I use javascript and css to build a multi-level drop down menu with following markups:</p>
  
  <pre><code>&lt;ul&gt;
     &lt;li&gt;menu item 1&lt;/li&gt;
         &lt;ul&gt;
           &lt;li&gt;&lt;a href="#"&gt;sub menu menu item 1&lt;/a&gt;&lt;/li&gt;
           ................. 
  </code></pre>
  
  <p>This markup is generated by a custom JSP tag <code>&lt;mui:menu .../&gt;</code> which loads menu data from a database.</p>
  
  <p>I hope my jsp page can behave like this:</p>
  
  <ul>
  <li>if menu data has not changed since last time I visited the page, just use browser's cache</li>
  <li>otherwise load from database...</li>
  </ul>
  
  <p>How can I do it? I don't know much detail about cache mechanism.</p>