Putting unix utility visible version info into ear, war, jar files?

Question

I would like to be able to use some unix utility (or java itself without a separate program) to display my version information for jar-like artifacts: ear, war, jar.
In other words, when I build one of these things, I'd like to put my SVN version, date, user name, and maybe some other stuff into it in a way that can be read without a custom program. This needs to be done as part of the ant build (without requiring a custom java program).
For example, one approach would be "strings | grep <special-string>" if I could put something, somewhere in the file that had this as 8-bit character encoding.
For jars, making the jar executable and having the main print it out works, but I don't think that's do-able for ears and wars, and it would be desirable to have a consistent approach.
Anyone already doing this?
Ideas?

Answer 1

For example, I don't think you can specify a mainline in the manifest of an ear or war.
They have pretty strictly defined formats, and I don't want to risk violating a standard by tinkering outside the standard.Possible, but you can always run it as java -cp myWar.war my.utility.Version.
There may be another possibility, but I'm unable to find any reference though:
In my early Java days, I used to work on a system where there was a Unix utility (called something like +"ident"+) that was able to extract version and description info stuffed in a .so file (under which "standard" or proprietary format was the info stored, I don't know).
I used to see it work on individual Java .class files too (from memory we had to put a String constant name "VERSION" in the class) and maybe jar files (I'm unsure).
One of my co-workers at that time had described that as a standard tool, but "ident" turns up nothing of that kind on Google... And I've never since encountered any description of the "VERSION" constant naming convention...
I was young and naive, I hope I were not bluffed by some alias in a custom setup... :o(
Edited by: jduprez on Feb 18, 2010 11:30 AM
OK a bit more reserah turned up [that man page|http://man-wiki.net/index.php/1:ident]. Apparently ident is part of RCS (installed along with CVS), and works by grepping the target file for patterns such as "$keyword: text $" (which is RCS/CVS keyword substitution pattern). Now that it mentions it, I remeber that that's what we put into our VERSION constant's value ("$version : ...$", or something of that kind).
So:
1) it's not so standard after all, you have to install the rcs package on the target host (regardless of whether you use RCS for configuration management, which would probably be a bad idea nowadays)
2) you have to put such formatted strings somewhere in your code or configuration files (easy with Ant, if not genuinely through Subversion)
3) To have it work on jar, war, ear, files, you have to make sure that the file is not compressed (otherwise the pattern might not appear in clear). I don't know whether that's easy to configure using Ant's jar, war, ear tasks.
A bit of a hassle compared to stuffing your own utility class and using java -cp...