I write the user"s status bar in a separate jsp file, and then include it in other jsp files. But one of the three websites can pop up the drop-down box, and the other two can"t.
<div class="btn-group">
<button type="button" class="btn btn-primary dropdown-toggle" data-toggle="dropdown" ><%=session.getAttribute("nickname")%></button>
<ul class="dropdown-menu" role="menu">
<li><a class="dropdown-item" href="-sharp"></a></li>
<li><a class="dropdown-item" href="javascript：void(0)" onclick="logout("<%=logoutPath%>")"></a></li>
</ul>
</div>