Simplify programmatic bootstrapping of an EntityManagerFactory

[lukasj]

Currently, I find it incredibly hard to bootstrap an EntityManagerFactory outside of a container. There are tons of blog posts out there who give advice on how to use PersistenceUnitInfo et al. to do that, but whenever I try these approaches, I'm wasting hours until I finally give up and resort to using some Spring utilities. This is how I can do it with Spring:

LocalContainerEntityManagerFactoryBean bean = new LocalContainerEntityManagerFactoryBean();
HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
adapter.setDatabasePlatform(SQLDialect.H2.thirdParty().hibernateDialect());
bean.setDataSource(new SingleConnectionDataSource(connection, true)); // pre-existing
bean.setPackagesToScan("org.jooq.example.jpa.entity"); // pre-existing
bean.setJpaVendorAdapter(adapter);
bean.setPersistenceUnitName("test");
bean.setPersistenceProviderClass(HibernatePersistenceProvider.class);
bean.afterPropertiesSet();

EntityManagerFactory emf = bean.getObject();

Observe that I have:

• A pre-existing DataSource or JDBC Connection (that's important, and cannot be done through persistence.xml)
• Pre-existing entities

That's it. I'm sure this can be done in an even simpler fashion in Spring, or, e.g. through javax.persistence.Persistence in a future JPA version.

Hope this helps

[lukasj]

• Issue Imported From: https://github.com/javaee/jpa-spec/issues/149
• Original Issue Raised By:@lukaseder
• Original Issue Assigned To: Unassigned

[gavinking]

Similar issues: #358, #114