JSP 1.1 had conflicting descriptions of tag handler pooling
requirements, and implementations had made conflicting assumptions. We
locked everybody involved in a closed room without food until white
smoke came up... You should consult JSP 1.2 for the results.
- eduard/o
Dennis Sosnoski wrote:
>
> Mac Ferguson wrote:
>
> > ...
> > Theoretically tags should be stateless, so these default values should be
> > being assigned in the doStartTag() method not in instance variable
> > declarations. Another part of the spec which was pointed out to me indicates
> > that successive calls to the same tag with the same attribute values may not
> > trigger the setter methods, here's the quote from the spec:
> >
> > "From the spec, JSP 10.1, "Once properly set, all properties are expected
> > to be
> > persistent, so that if the JSP container ascertains that a property has
> > already
> > been set on a given tag handler instance, it needs not set it again.""
> >
> > which once again implies that if any instance-specific initialization needs
> > to be done in a tag, it should be done in doStartTag() or some submethod
> > which will be called on every use of the tag instance.
> >
> > My first thought was that release() should be implemented to reset state,
> > but the comments for the lifecycle diagram on page 165 of the spec indicate
> > that release is "intended to be for relleasing long-term data" and there is
> > no guarantee that properties are retained or not.
>
> 5.4.2 of the JSP 1.1 spec says explicitly that "Once all invocations on the tag
> handler are completed, the release method is invoked on it. Once release method
> is invoked all properties are assumed to have been reset to an unspecified
> value."
>
> Unless something has changed in 1.2 release() is what should be resetting the
> state, including all the property values. That still leaves the issues from
> Shawn's email regarding properties set for one use of the tag carrying over to
> another use of the tag.
>
> I'd suggest that the spec should either require reset to be called before a tag
> is reused (at least with a different set of attributes), or should have some way
> of explicitly setting an attribute to the unused state. I haven't looked into
> 1.2 to see if it has such a requirement, though.
>
> - Dennis
