I'm bundling: {appResources=RelativeFileSet{basedir:/tmp/testBundlerWorkDir5463040229930083923/jars, files:[rmApp.jar]}, mainJar=RelativeFileSet{basedir:/tmp/testBundlerWorkDir5463040229930083923/jars, files:[rmApp.jar]}, fileAssociations=[{fileAssociation.extension=[foo, bar], fileAssociation.contentType=[application/example], fileAssociation.description=The sample description}, {fileAssociation.extension=[baz, qux], fileAssociation.contentType=[hello/world], fileAssociation.icon=/export/home/gtee/dginzburg/appBundlerTests-8u40/build/classes/com/oracle/appbundlers/utils/resources/icon2.png}], classpath=rmApp.jar}

So, at least, "xdg-open /path/to/a.foo" should remove this file, if it exists (rmApp is just the application, which removes the file), but instead I get this output:
/usr/bin/xdg-open: line 402: htmlview: command not found
Then the Firefox browser is opened and it suggests opening with "RmApp (default)"