How to connect to multiple databases in Hibernate

user_233804 0
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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?

hibernate database
6 Answers

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.

user_146190

Ideally you should move to Distributed transaction type of system[using Java Transaction Analyzer org.hibernate.transaction.JTATransactionFactory] in this case. If you are running in JBoss App Server, you can do it by using "Distributed Transaction Managers". You can learn more about it here.

Shamik_Majumdar_613950

You can also use a catalog with the value of the other database

@Table(name = "foo", schema = "bar", catalog = "OtherDatabase")

user_144670

You can also Add mapping class in configuration.xml file

Note : this is for annotations and for resources use resources keyword instead of class

<mapping class="packageName.classNmae1"/>
<mapping class="packageName.classNmae2"/>
user_88189430
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