How does one know version of Apache POI is installed?

While working on (surprise) ColdFusion 9 server upgrades, I encountered issues with the new version of Apache POI and existing libraries. I looked into the $CF9/WEB-INF/cfusion/lib directory to find a file simply named poi.jar. On ColdFusion 8, the filename was poi-2.5.1-final-20040804.jar which makes the version number obvious. Spoiler Alert: It's 3.5 beta 7 -- not too far behind the current release of 3.6.

I figured there would be a clue within the JAR of the version number, and there is. The org.apache.poi.Version class has a public main method that prints the version number. Neato.

cd $CF9 jar -tf WEB-INF/cfusion/lib/poi.jar | grep -i version org/apache/poi/Version.class java -cp WEB-INF/cfusion/lib/poi.jar org.apache.poi.Version Apache POI 3.5-beta7 (20090726)

Knowing what the proper Apache POI class name is, we could do the same thing from within a CFML page:

<cfset poi = createObject("java", "org.apache.poi.Version")/><cfoutput>#poi.getProduct()# #poi.getVersion()# #poi.getReleaseDate()#</cfoutput>

Viola.