Lesson 17 (ORM Part 2)

Lesson 17: Relationships in Object-Relational Mapping

In the prep work for this lesson, the students learned

1. How to persist model classes that have one-to-many and many-to-one relationships.
2. How these relationship types are represented in a SQL database.
3. How to DRY code using an AbstractEntity, annotated with @MappedSuperclass

Announcements

1. Check with your course manager for any additional announcements.

For Part-Time Students:

1. Assignment #4 is open and students should be actively working on it. After today's class, students will be able to complete all but Part 4.

For Full-Time Students:

• Welcome to Day 26!
• Assignment 4 Work Time scheduled for Days 28 - 31!

Large Group Time (Instructor)

Lesson 17 Topics That Require Careful Attention

1. Again, review the relationship between Java classes/objects and database tables/rows.

2. Address the inverse relationship of one-to-many and many-to-one related classes.

3. Touch upon the fact that these types of relationships between classes need not be bi-directional.

4. Confirm that students understand the benefit that AbstractEntity provides and what @MappedSuperclass does.

5. Discuss the CrudRepository interface and how to use and research its methods.

   a. The in-book coding-events example makes use of .findById(), which returns an Optional instance. It would also be wise to discuss this class briefly.

Small Group Time: Lesson 17 Studio (TA Notes)

1. Studio time in today's class is reserved to work on Assignment 4.
2. Please take the time to complete the assignment yourself before class, or at least get familiar with the tasks at hand. Offer your experience solving the various parts or setting up the database so that you may share any stumbling blocks you may have encountered.
3. The material presented for today's class gives students the ability to finish Parts 1-3: Setting Up the Database, Persisting the Model Classes and Leveraging an AbstractEntity Class, and Setting Up a One-To-Many Relationship Between Objects.
4. Some students may have difficulty creating a new techjobs schema and correctly linking to this in their Spring app. Or they may struggle with creating a new MySQL user and assigning the right permissions. be on the lookout for these issues as these will impede progress with the rest of the assignment.