Grrr... it seems we may need to reopen this, i didn't realize until just now that the previous patch (including "fail on warnings unless 1.4" was already committed) and my recent tweak to the build.xml so that all contribs get their javadocs built has spanwed some more warnings/problems that i didn't notice before because i was using 1.5 (and apparently so is hudson because the nightly build is still working).
Note, if you are using java 1.5 and wnat to reproduce these problems, use...
ant -Dant.java.version=1.4 javadocs
1) running javadocs on a virgin checkout does not force contribs that download their dependencies on the fly to do so – the javadocs task currently has no dependencies that relate to contribs, so "ant javadocs" or even "ant package" will get errors from things like contrib/db because the sleepycat jar has never been downloaded.
(NOTE: you can NOT reproduce this by running "ant clean javadocs" ... the clean target doesn't remove lib jars that contribs download on the fly .. if you've ever build contribs you've got the jars and it will mask this bug)
Possible solution: make "javadocs" depend on build-contrib ? or a new task that does the contrib-crawl and calls whatever task contribs use to fetch third party jars?
2) even if all the jars are downloaded, and running in 1.4 mode so current gdata errors are ignored, there are still 3 warnings...
[javadoc] javadoc: warning - Multiple sources of package comments found for package "org.apache"
[javadoc] javadoc: warning - Multiple sources of package comments found for package "org"
[javadoc] javadoc: warning - Multiple sources of package comments found for package "org.apache.commons"
...my first guess is that multiple lib jars in the contribs had package.html files for these packages ... but i can't find evidence of that ... i haven't tried the trial and error approach of commenting out contribs one at a time until those errors go away to try and track down the source of the problem
3) Hudson seems to be running the nightly build using java 1.5, so the hook to ensure that there are no javadoc warnings isn't getting triggered.