What is the use of bag tag in Hibernate?

Question

I need to know how to use the bag tag and what is the purpose of it?

Answer 1

For collection mapping

If your table does not have an index column, and you still wish to use List as the property type, you can map the property as a Hibernate < bag>. A bag does not retain its order when it is retrieved from the database, but it can be optionally sorted or ordered.

http://docs.jboss.org/hibernate/core/3.3/reference/en/html/collections.html

Answer 2

From the API:

A bag is an unordered, unkeyed collection that can contain the same element multiple times. A bag permits duplicates, so it has no primary key. The Java collections API, curiously, has no Bag.

Answer 3

A short and simple answer:

You don't need to use the <index> tag when mapping an unsorted List and you also don't need an additional index column in database.

Unlike a List a Bag does not persist the order of its elements, but you can specify an order-by parameter to retrieve its elements in a specific order.