CODEWITHSUNDEEP
javahibernateormhibernate-mapping
gokul
gokul

Reputation: 153

What is the use of bag tag in Hibernate?

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

Upvotes: 13

Views: 15149

Answers (3)

Rafael Borja
Rafael Borja

Reputation: 4917

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.

Upvotes: 2

McGin
McGin

Reputation: 1401

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.

Upvotes: 3

Damian Leszczyński - Vash
Damian Leszczyński - Vash

Reputation: 30875

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

Upvotes: 8

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