Depends on the app server. Tag caching and pooling is going to be a new thing in JRun 3.1, which is coming out in beta 1 soon (next week). I don't know how
Tomcat and others handle it.
I predict by the end of the year everyone will support efficient tag reuse and pooling, but there were a lot of disagreements about how to do it on the JSP spec group during the 1.2 specification development. How you do it largely depends on when release() is called on a tag handler and what that should do, and this was a matter of contention among various vendors and experts involved in the spec.
Take a look at the generated
Servlet code to see how your JSP tags are handled on the back end. Also note that with the modern, optimizing-JIT JVMs (especially HotSpot and Sun & IBM 1.3 JVMs), object creation and deletion for short-lived objects is cheap, and pooling can actually interfere with the optimizing JVM's management of allocation and garbage collection.
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Scott Stirling
Author of
Java Server Pages Application Development
[This message has been edited by Scott Stirling (edited March 07, 2001).]