As to *why* you want this... that's a more interesting question. JSP is a poor technology for generalized out-of-container templating; I'd consider using something else, like FreeMarker, Velocity, etc.
It's unclear what you want to do with the import result, but if you're using JSP here are a couple of options provided by JSTL:
1) Use to capture the result in a scoped var of type String without including it in the page's output. You can always include it later if you want.
2) Use to expose a scoped var of type Reader that can be used to process the result without including it in the page's output. In this case, importReader has nested visibility - meaning that it cannot be accessed after the end tag for <c:import>. The <util:importHandler> tag is just an example and you would need to either create your own tag or use an existing one. A "real" example that parses the result into a scoped var of type Document:
Here. Have a potato. I grew it in my armpit. And from my other armpit, this tiny ad: