Spring, for example, injects a proxy of type SharedEntityManagerCreator.Įvery time we use the injected EntityManager, this proxy will either reuse the existing EntityManager or create a new one. However, the container (JakartaEE or Spring) injects a special proxy instead of a simple EntityManager here. It seems that one EntityManager instance should be shared for all operations. However, things get counter-intuitive when using container-managed EntityManagers: class MovieService // or even EntityManager entityManager When using application-managed EntityManagers, it’s easy to create thread-confined instances: EntityManagerFactory emf = // fetched from somewhere ![]() ![]() This means that each thread should obtain its instance, work with it, and close it at the end. On the other hand, the EntityManager instances aren’t thread-safe, and are meant to be used in thread-confined environments. So it’s completely safe in concurrent contexts to write: EntityManagerFactory emf = // fetched from somewhereĮntityManager em = emf.createEntityManager() ![]() The EntityManagerFactory instances, and consequently, Hibernate’s SessionFactory instances, are thread-safe. Container and Application Managed EntityManager Based on these properties, Hibernate connects with the underlying database. This file contains the configuration for the EntityManager: Īs we can see, we define the persistence-unit that specifies the underlying datastore managed by the EntityManager.įurthermore, we define the dialect and the other JDBC properties of the underlying datastore.
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