Message Title

I have attached a simple, one-Servlet project that duplicates this issue. You can also see the issue reported in this Stack Overflow question (I didn't post that) and this forum post (posted by the same person it appears).
The attached project worked fine with Hibernate 4.2.x and through Hibernate 4.3.0.Beta4. I have not tested with 4.3.0.Beta5-4.3.0.CR1, but 4.3.0.CR2 and 4.3.0.Final result in the following error on Tomcat 7 and 8:
javax.persistence.PersistenceException: Unable to build entity manager factory
	org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:81)
	org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:54)
	javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
	javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
	com.wrox.site.EntityServlet.init(EntityServlet.java:49)
	javax.servlet.GenericServlet.init(GenericServlet.java:160)
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:76)
	org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:934)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522)
	org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1015)
	org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:646)
	org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1576)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1534)
	java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	java.lang.Thread.run(Thread.java:744)

root cause
org.hibernate.engine.jndi.JndiException: Unable to lookup JNDI name [java:comp/env/jdbc/EntityMappings]
	org.hibernate.engine.jndi.internal.JndiServiceImpl.locate(JndiServiceImpl.java:117)
	org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.configure(DatasourceConnectionProviderImpl.java:115)
	org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:89)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:206)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:178)
	org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:260)
	org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:94)
	org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:89)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:206)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:178)
	org.hibernate.cfg.Configuration.buildTypeRegistrations(Configuration.java:1885)
	org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1843)
	org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:850)
	org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:843)
	org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:399)
	org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:842)
	org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:73)
	org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:54)
	javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
	javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
	com.wrox.site.EntityServlet.init(EntityServlet.java:49)
	javax.servlet.GenericServlet.init(GenericServlet.java:160)
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:76)
	org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:934)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522)
	org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1015)
	org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:646)
	org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1576)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1534)
	java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	java.lang.Thread.run(Thread.java:744)

root cause
javax.naming.NameNotFoundException: Name [java:comp/env/jdbc/EntityMappings] is not bound in this Context. Unable to find [java:comp].
	org.apache.naming.NamingContext.lookup(NamingContext.java:820)
	org.apache.naming.NamingContext.lookup(NamingContext.java:153)
	javax.naming.InitialContext.lookup(InitialContext.java:421)
	org.hibernate.engine.jndi.internal.JndiServiceImpl.locate(JndiServiceImpl.java:114)
	org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.configure(DatasourceConnectionProviderImpl.java:115)
	org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:89)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:206)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:178)
	org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:260)
	org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:94)
	org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:89)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:206)
	org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:178)
	org.hibernate.cfg.Configuration.buildTypeRegistrations(Configuration.java:1885)
	org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1843)
	org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:850)
	org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:843)
	org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:399)
	org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:842)
	org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:73)
	org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:54)
	javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
	javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
	com.wrox.site.EntityServlet.init(EntityServlet.java:49)
	javax.servlet.GenericServlet.init(GenericServlet.java:160)
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:76)
	org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:934)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522)
	org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1015)
	org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:646)
	org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1576)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1534)
	java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	java.lang.Thread.run(Thread.java:744)
It would appear that, starting somewhere in 4.3.0.Beta5, 4.3.0.CR1, or 4.3.0.CR2, Hibernate stopped being able to resolve JNDI DataSource resources in Tomcat. This makes Hibernate 4.3.0.Final completely unusable, meaning this is a blocking issue. Until this is fixed, I will have to downgrade to 4.3.0.Beta4.
The reporter of the Stack Overflow question and forum post believes he has found the likely culprit: a change in the JndiServiceImpl#locate method.