How to insert multiple rows into database using hibernate?

With the save() method in a session, Hibernate couples the object to a row and this relation remains while the session remains active. Therefore, if you use the same object, you actually update the existing row. The solution is to construct a new object for every row. In this case:

for (String item : items)
{
  Feature feature = new Feature();
  feature.setName(item);
  session.save(feature);
}

There's a very nice chapter about batch processing in the Hibernate docs.

Set the property

hibernate.jdbc.batch_size 20

Then use this code

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

for ( int i=0; i<100000; i++ ) {
    Customer customer = new Customer(.....);
    session.save(customer);
    if ( i % 20 == 0 ) { //20, same as the JDBC batch size
        //flush a batch of inserts and release memory:
        session.flush();
        session.clear();
    }
}

tx.commit();
session.close();

Make sure you consider the implications for your id-generation strategy e.g. discussed here.

Update 2015-09-23

I finally found the time to sit down and write a detailed article at https://frightanic.com/software-development/jpa-batch-inserts/.