Rony
RF> If possible I would like to write a single tagclass, but use it
RF> for two or more different tags, as the implementation would share
RF> quite a lot of code. Besides, it might be helpful for debugging.
CS> Feel free to build a base class with the shared code and then implement
CS> the differences in subclasses.
Sure, implementing a sub-class of TagSupport that acts as a custom tag
super-class works fine.
RF> I would have a need to find out the tag name
RF> that caused the tagclass to run.
RF>
RF> Is this possible? If so, how would one be able to get at
RF> that tag name (any brief hints would suffice) ?
Not sure exactly what you mean...
Here's an example:
- CustomTagImplementation.java contains:
public class CustomTagImplementation extends TagSupport
- tags.tld contains:
<tag>
<name>CustomTag1</name>
<tag-class>tags.CustomTagImplementation</tag-class>
</tag>
<tag>
<name>CustomTag2</name>
<tag-class>tags.CustomTagImplementation</tag-class>
</tag>
- page.jsp contains:
<td>
<tags:CustomTag1 />
</td>
Are either of these what you mean?
A. Get surrounding tag "<td>" - TagSupport/CustomTagImplementation/getParent(),
for calculating something like an xpath?
B. Get tag definition name "CustomTag1" - Ouch. Sorry, no help there. How
about an intellectual exercise to kill some time? :-)
Suppose you had a map of classes and associated tag names from either parsing
tags.tld directly or exposing whatever structure holds classes instantiated
from it. You might still have a lookup problem due to a one-to-many
relationship. Using CustomTagImplementation/getClassName() as the map lookup
key would have 2 theoretical answers, both "CustomTag1" and "CustomTag2".
By the time the page code is executed, the JSP has aleady been compiled.
Looking at pre-compiled org/apache/jsp/page_jsp.java, each call to
<tags:CustomTag1 /> gets its own _jspx_meth_* method. There is a comment in
each method, "// tags:CustomTag1". Seems kinda messy in there, and
potentially fragile to depend on the pre-compiler output format.
It's too bad TagSupport is not auto-magically fed as a parameter the name of
tag definition in the page that "called" it. All in the engine, no changes to
JSP pages.
While I have not used it myself, have you looked at SimpleTagSupport to see if
it has something useful?
--
Cris Berneburg
CACI Senior Software Engineer
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