getPersistenceUnitRootUrl() - JPA PersistenceUnitInfo's method

URL getPersistenceUnitRootUrl()

Returns the URL for the jar file or directory that is the root of the persistence unit. (If the persistence unit is rooted in the WEB-INF/classes directory, this will be the URL of that directory.) The URL will either be a file: URL referring to a jar file or referring to a directory that contains an exploded jar file, or some other URL from which an InputStream in jar format can be obtained.
a URL referring to a jar file or directory
JPA 1.0

This documentation page is derived (with some adjustments) from the open source JPA 2 RI (EclipseLink)
and is available under the terms of the Eclipse Public License, v. 1.0 and Eclipse Distribution License, v. 1.0.
Object Relational Mapping (ORM) JPA 2 providers include Hibernate, EclipseLink, TopLink, OpenJPA and DataNucleus.
ObjectDB is not an ORM JPA implementation but an Object Database for Java with built in JPA 2 support.