Advance Hibernate Mapping Overview

Basic Mapping:

Advance Mappings

• In the database you most likely will have
  • Multiple tables
  • Relationships between Tables
• Need to model this with Hibernate

Advanced Mappings Type

1. One-to-One
2. One-to-Many, Many-to-One
3. Many-to-Many

Important Database Concepts

• Primary key and foreign key
• Cascade

Primary Key and Foreign Key

• Primary Key: identify a unique row in a table
• Foreign Key:
  • Link tables together
  • A field in one table that refers to primary key in another table

Cascade

• You can cascade operations
• Apply the same operation to related entities
• Whenever an object will be saved in the table “instructor”  then simultaneously the object will also be saved within another table “instruction_details”.

• If we delete an instructor, we should also delete their instructor_detail.
  • This is known as ” CASCADE DELETE “

Note: We should not perform cascade deletion operation in Many-to-Many mapping.

Fetch Types: Eager vs Lazy Loading

• When we fetch / retrieve data, should we retrieve EVERYTHING?
  • Eager will retrieve everything in a single shot
  • Lazy will retrieve on request

Uni-Directional Relationship

• Is a one way relationship
• You have an “instructor” and then you have “instructor_detail”, so you will start with instructor object you load the instructor and then from there access the instructor detail.

Bi-Directional Relationship

• Instructor and then they have its relation with instructor detail, but then also we can go the other way. So we can load the instructor details and have a reference to the instructor.