How to connect to multiple databases in Hibernate

Question

I am new bee to Hibernate and trying out things. One thing that seems to amuse all is how to connect to different databases? I have two questions here:

1. If in the same web app I need to connect to MySQL and Oracle, how do I do it?
2. I am using MySQL and have two databases test1 and test2, how to connect and retrieve data?

I have read in a blog that we can create different configuration files and do it. I tried it but was not sucessful. Here's what I tried:

SessionFactory sf = (SessionFactory) new Configuration().configure(path);

Where path is the path of the config file. Is this the right way?

Answer 1

Using annotation mappings as an example:

Configuration cfg1 = new AnnotationConfiguration();
cfg1.configure("/hibernate-oracle.cfg.xml");
cfg1.addAnnotatedClass(SomeClass.class); // mapped classes
cfg1.addAnnotatedClass(SomeOtherClass.class);
SessionFactory sf1 = cfg1.buildSessionFactory();

Configuration cfg2 = new AnnotationConfiguration();
cfg2.configure("/hibernate-mysql.cfg.xml");
cfg2.addAnnotatedClass(SomeClass.class); // could be the same or different than above
cfg2.addAnnotatedClass(SomeOtherClass.class);
SessionFactory sf2 = cfg2.buildSessionFactory();

Then use sf1 and sf2 to get the sessions for each database. For mapping files, you just use cfg.addClass instead of addAnnotatedClass. Put the cfg.xml files in the root package in this case. Those will have the Oracle or MySQL dialect and connection information.