Since version 7 OpenCms is a Servlet 2.4 and JSP 2.0 conforming application. In addition to the improved expression language (EL) JSP 2.0 also brings in the possibility of developing custom tags(actions) using JSP rather than writing Java code. This allows for some pretty neat things and enables you to go one step further towards cleaner view code. I’ve used this in one of my last projects extensively to refactor common code like pagers and link generation. For example:
<cms:include file="/system/modules/com.example.ocms.commons/elements/pager">
<cms:param name="currentPage">
<c:out value="${model.currentPage}"/>
</cms:param>
<cms:param name="pageCount">
<c:out value="${model.pageCount}"/>
</cms:param>
</cms:include>
Became:
<wt:pager model="${model}"/>
Not does it only look cleaner and is much more focused, it also decouples your view more from the underlying CMS solution. Of course you could also develop a custom tag library using Java (which I have done a few times) but using a JSP the advantage that code can be changed on the fly and even from a web designer. You can always refactor your JSP taglib into a Java one if you need to do it. There are some limitations of JSP tag files (like you can’t use scriptlets in the body) but they are easy to get around.
But as always: This is no silver bullet. There are problems with tag files which may not be obvious at the first glance.
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