What does “INFO: TLD skipped. URI is already defined” mean?

Question

When running my JSF 2 application in eclipse I am getting several info logs that TLD was skipped because it\'s already defined as follows:

Answer 1

Priority order of URIs required by spec is:

J2EE platform taglibs - Tomcat doesn't provide these

web.xml entries

JARS in WEB-INF/lib & TLDs under WEB-INF (equal priority)

Additional entries from the container

Tomcat loads tld twice.

1, when Tomcat starts up, it loads tld to find listeners in tld files.

2, when first jsp file is compiled, it build a cache of tld pairs.

1, load tld to find listeners in tld files

When loading from web.xml, it puts taglib-uri from web.xml and uri from tld file into a set. When loading from WEB-INF or jar, the uri is from tld file.

Tomcat needs to avoid duplicate tld listener adding, so it checks whether uri exists in the set. If uri already exists, it logs the messages you post and skip adding tld listener.

2, build cache

1) web.xml entries, the tag uri is got from web.xml

2) scan tld files under WEB-INF, the tag uri is got from tld files

3) scan jars, the tag uri is got from tld files.

If uri aready exists, the entry will be ignored.