How can I make a JPA application access different databases?

Question

I\'m writing a Java SE (desktop) application that has to access different databases all of which will have the same data model (same schema, tables, etc.). I want to reuse

Answer 1

You can create EntityManagerFactory at runtime by providing properties.

Map properties = new HashMap();

properties.put(TRANSACTION_TYPE, PersistenceUnitTransactionType.RESOURCE_LOCAL.name());
properties.put(JDBC_DRIVER, driver);
properties.put(JDBC_URL, db_url);
properties.put(JDBC_USER, "userName");
properties.put(JDBC_PASSWORD, "password");

EntityManagerFactory factory = Persistence.createEntityManagerFactory("PERSISTENT_UNIT_NAME", properties);

Also you can try having a property file from which properties will be loaded at runtime into map. Therefore it will decouple the database configuration from code.

Edit : The property keys(JDBC_URL etc) are vendor specific, they should be replaced accordingly.