TransactionalDriver consuming all database connections

I'm using Narayana in a Spring / Hibernate Set Up for running a distributed Infinispan cache. During the start up of the application Spring Security is fetching several access control entries from the database. These are several hundred requests. The TransactionManager is creating always a new connection and I can see in the PostgreSQL console that all connections are used up until PostgreSQL is not allowing any connections anymore.

What is needed is a blocking feature. I think Apache DBCP has something like this and is blocking calls until connections are available again.