The connection pool specifies the underlying database connection which can be used explicitly if needed without using any of the JPA extras. The persistence.xml file specifies the extras specific to JPA, one of which is an interpretation of how to talk to the various database models out there which i think should be separate from the connection parameters.
I agree it would be nicer if the persistence.xml contents could be specified as annotations and injected at runtime as has happened for many of the other configuration features that needed to be specified in XML files.
As for it not working, which version of glassfish are you using? I've got this working with one of the more recent promoted builds (i'm currently about 4 behind), but will try with the latest build.
I
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