hibernate中的一对多关联

Question

The hibernate documentation gives some rules when we use one-to-many association in Hibernate:

http://docs.jboss.org/hibernate/orm/3.3/reference/en-US/html/collections.html#collections-onetomany

A one-to-many association links the tables of two classes via a foreign key with no intervening collection table. This mapping loses certain semantics of normal Java collections:

• An instance of the contained entity class cannot belong to more than one instance of the collection.
• An instance of the contained entity class cannot appear at more than one value of the collection index.

Please help me in understanding these statements.

Suppose I have a Product and it has collection of parts, now as per the points what kind of restrictions applied on my Product and its parts?

Answer 1

• A Part cannot belong to 2 or more Products
• A Part cannot appears more than one time in the Collection of Parts of a Product