cannot override persistence unit property in JBoss 6M5

[llraj]

I want to override the datasource specfied in persistence.xml.

Persistence.createEntityManagerFactory(<PU name>, <map>) is returning null.

<map> contains javax.persistence.nonJtaDataSource set to JNDI name of new datasource.

I played around with Ejb3Configuration with no luck.

I basically need to create an Entity Manager Factory without using persistence.xml since the datasource will not be known until runtime.