Creating a many to many association - BiDirectional

Continuing from the last post, I shall now make the Person Chocolate relation bidirectional. This means that chocolate will also hold a collection of its fans. Instead of using a set here, I decided to use a bag. The updated java files are as below:

Creating a many to many association - UniDirectional

After one to many, its time to try a many-to-many association. This association is rarely used , instead being replaced with 2 many-to-one associations. For this example I decided to create two entities- people and chocolate (ya am still on chocolates only :) ). Many people like mannnnnnnnnnnnnnnny chocolates. As we are considering unidirectional relation, the mapping can be seen from the People class only.

One To Many association that is optional

We have seen one to many relations before but Hibernate also supports an optional one to many relationship. Consider chocolates and Bags. There is a possibility that some chocolates exists outside of a bag. Every chocolate can at any given time be in one and only one bag. However a particular chocolate may also not be in any bag. This makes the one to many relation an optional association.

One to One Association Using Foreign Key

In the earlier technique I  mapped a one-to-one relation using a shared primary key. Now I shall attempt to create the same relation-ship using foreign keys.
Both the tables in this case will have their own independent primary key and id generation strategies. One of the tables (mostly the entity owning the relation, in this case the Order_Data) has  a column which references the primary key from the other table.

One to one association that is optional

In previous posts I have tried out one to one associations involving shared primary keys and foreign keys.In the that example an Order had a one to one relation between BillDetail.Consider the scenario wherein an Order is created separately from the BillDetail. The Bill Detail information is added at a later date. This means that the one-to-one relation between the two entities is optional and may not be always present.The relation would require that