Using Liferay Util Body Top
The body top tag is not a self-closing tag. The content placed between the opening and closing of this tag is moved to the top of the body tag. When something is passed using this taglib, the body_top.jsp is passed markup and outputs in this JSP.
This tag also has an optional outputKey attribute. If several portlets on the page include the same resource with this tag, you can specify the same outputKey value for each tag so the resource is only loaded once.
The example configuration below uses the <liferay-util:body-top> tag to include JavaScript provided by the portlet’s bundle:
<liferay-util:body-top outputKey="bodytop" >
<script
src="/o/my-liferay-util-portlet/js/my_custom_javascript_body_top.js"
type="text/javascript"></script>
</liferay-util:body-top>
Now you know how to use the <liferay-util:body-top> tag to include additional resources in the top of the page’s body.