Lesson - 62 : Hibernate - Many To Many Using idbag tag using XML and Annotation based Config

Hibernate – Assotations/Relationship : ＜idbag＞ Tag In Hibernate :
1. While working with many-to-many relationship a join table of relationship contains foreign keys. The foreign keys in the table contains duplicate values.
2. In order to maintain the data easily in a join table there is a need of primary key also for the join table.
3. If a primary key column is also added for a join table then we need to inform about primary key column to the hibernate by configuring ＜idbag＞ tag in the mapping file or hbm file of the hibernate.
5. If a primary key column is added for a join table then the value to that primary key column should be generated by hibernate only. A developer can not assign the primary key values for join table.
6. Under ＜idbag＞ tag, we configure ＜collection-id＞ tag to configure primary key column of join table.
7. Under ＜collection-id＞ tag the generator class should be other than assign.

Course Table :
＜set name="students" cascade="all" table="STUDENTS_COURSES"＞
＜key column = "CID" /＞
＜/set＞

Student Table:
＜idbag name="course" cascade="all" table="STUDENTS_COURSES"＞
＜collection-id type="int" column="s-c-id"＞
＜generator class="increment"/＞
＜/collection-id＞
＜key column = "STUID" /＞
＜/idbag＞