Hi Mr. Slim,

this was asked many moons ago in another forum--might be useful, might
be junk.  Here's the link, nonetheless:

http://groups.google.com/group/weblogic.developer.interest.jsp/browse_frm/thread
/8319e1f3a6a52728/421d9e3e61f90655?lnk=st&q=threading+custom+tags+jsp&rnum=2&hl=
en#421d9e3e61f90655

or, if'n that broke, here it is again:

http://linkfrog.net/dabl

Bye, Abigale

I don't think so. If that was the case all tags would be non thread-safe. Tag instances are created
and gc'ed once the response is generated.

.k

No, tags work in a different way to Servlets. A tag object is only in
use at one point by one request at a time. That allows properties to be
set on the instance and state to be kept.

Depending on the JSP implementation, the tag object may or may not be
reused. If it is reused, it will never be in simultaneous use and is not
responsible for synchronisation. Most tag creation is little more than
memory allocation, and therefore pooling is of dubious benefit. The
reuse of tags is not done through weak reference or other uses of the
garbage collector, so the JSP implementation has no reasonable way of
detecting abuses. IIRC, the JavaDocs have some basic state diagrams.

Because a tag can be reused, you should not keep any references to it
outside of its scope. This is roughly analogous to storing request state
in a servlet instance variables. I have seen programmers attempting to
"reuse" the tag class. It doesn't work, and isn't very good style
anyway. The only clients of a tag should be the JSP page and other tags
through ancestry. If you need to keep any state beyond the tag, copy it
into a new class.

Obviously, the use of static variables is generally thread-hostile, and
should be avoided.

Tom Hawtin