Reference taglibs in web.xml

Question

Hi,
I'm trying to find a way to avoid having to always reference commonly used taglibs in all my jsps. Its kind of a hassle to manually change all references when the taglib.tld changes name.
I looked at the <tag-lib> element for web.xml and am a little confused as to what purpose it serves. Does anyone know if this is suppose to provide the functionality I want or is used for earlier jsp specifications? Thanks.

Answer 1

Which taglibs are you having trouble with that keep renaming their taglib.tld? Are they custom ones or standard ones available over the net?
There are two methods of doing this, one by specifying a uri inside the taglib (like JSTL does) the second by setting up mappings in web.xml.
The web.xml file can provide a mapping between the uri you specify in the jsp, and the actual tld file.
So for example if you have in your jsp:
<%@ taglib prefix="test" uri="http://my.testtag" %>in web.xml you would have the following:
  <taglib>
    <taglib-uri>/http://my.testtag</taglib-uri>
    <taglib-location>/WEB-INF/mytag.tld</taglib-location>
  </taglib>This sets up the mapping between the uri you used, and the actual tld on disk
Now if the name of the tld file changes, all you do is change it in web.xml, and all your jsp pages will point at it.
The better method IMO is to use the <uri> element in the tld file.
For instance taking an example from JSTL 1.1 , c.tld
<taglib>
<uri>http://java.sun.com/jsp/jstl/core</uri>
...The c.tld file is bundled with the JSTL file standard.jar in the META-INF directory.
This lets your jsp page just import the taglib with the uri, and the server will find it in the appropriate jar file. No need for any entries in web.xml to do this.
If the tag library is written half-decently nowadays, they follow this pattern, and installing a new taglib becomes painless.
Hope this helps,
evnafets