How can a JSP fragment include its dependencies into the parent's head tag?

Question

I have a JSP file called header.jsp which looks like this.

<%@ taglib prefix="c" uri="/c" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<!DOCTYPE html>
<html>
<head>
...
</head>
<body>

I then have a content fragment which looks like this.

<jsp:include page="../header.jsp" />
My Page Content Here.

If that content fragment has certain dependencies like CSS and Javascript includes which have to go inside the head tag, how can I include them there? Each fragment might have its own set of CSS and Javascript files which are different, and I don't want to include every single possible CSS and Javascript file I might use into the header for every single page. What's the proper way to handle this? I'm a dumb intern at a startup, so forgive my ignorance. Thank you in advanced.

Simple c:import templating might be enough if your needs are minimal. That said, is there *enough* different CSS/JS to make it worth the effort? After compression, they tend to be relatively small, compared, say, to images. — Dave Newton, Jul 09 '12 at 18:28

score 3 · Answer 1 · edited May 23 '17 at 10:32

It's easy, you can do the following by using <jsp:invoke /> tag instead of the <include /> tag. It's new for jsp 2.0 and allows you to take some fragments from one page to another, making very easy the task of building templates. You can check a tutorial here.

And this is the way to solve your problem: Create a tag folder and put this in it.

template.tag

<%@tag description="Main template of the page" pageEncoding="UTF-8" trimDirectiveWhitespaces="true" %>

<%@attribute name="header" fragment="true" required="false" %>
<html>
    <head>
        ...some css and javasctipt used on all the pages...
        <!-- Custom css and javascript for one page -->
        <jsp:invoke fragment="header"/>
    </head>
    <body>
        <jsp:doBody />
    </body>
</html>

Use the previous template on your page by including the tag folder:

useOfTemplate.jsp

<%@page contentType="text/html" pageEncoding="UTF-8" %>

<%@taglib prefix="custom" tagdir="/WEB-INF/tags" %>

<custom:template>
    <jsp:attribute name="header">
        ...Here you can include your custom css and javascript for this page...
    </jsp:attribute>
    <jsp:body>
        ...here comes the info of the page...
    </jsp:body>
</custom:template>

How can a JSP fragment include its dependencies into the parent's head tag?

1 Answers1