CodeLab

This CodeLab exercise is designed to help you practice the concepts you have learned on the first day of JPA part 2. You will be working on a series of tasks that involve Java Persistence API, with Entities and DAOs.

1. Create a new Maven project getting ready for JPA with Hibernate. Use the JPA setup in IntelliJ guide to help you - or use your own starter project / template.
2. Make sure your .gitignore file is set up correctly and then initialize a new Git repository in your project folder. Add and commit your files.

1. Each member should create a database in your docker environment with postgres called university.
2. Set up config.properties with the database name, so Hibernate can connect to the database.
3. Also, you might want to connect to the database with IntelliJ’s database tool window to see the tables that Hibernate creates.

You are going to create a simple application for a university. The application should be able to manage students, courses and teachers. This time around we are going to add relationships between the entities. The relationships can be seen in the class diagram above. You need to implement the entities and DAO methods. Make sure to use the correct annotations for the relationships and try to understand how the relationships work.

Remember to test the DAO methods as you go along. It’s fine to use the Main class for ad-hoc testing

Ask yourself the following questions before you start implementing the relationships:

• What are the relationship between the entities?
• Which one should be the owning side of the relationship and what does that mean?
• Should the relationship be unidirectional or bidirectional?
• What cascade type should be used or should we use them at all? What are the implications?
• Should we use fetch type eager or lazy and why?

The following tasks are suggestions. You can add more tasks as you go along. Read through the list, and get going.

1. Create an Enum for the Course class as shown in the diagram and add the correct annotations to the Course class.

2. Create a Teacher entity class as shown in the diagram.

3. Create a Student entity class as shown in the diagram.

4. Create a Course entity class as shown in the diagram.

5. Add the relations between the entities as shown in the diagram.

   • a) a student can attend one course
   • b) a course can have many students
   • c) course can have only one teacher
   • d) a teacher can teach many courses

6. Create a generic DAO interface with CRUD methods. Call it IDAO. CRUD would be create, getAll, getById, update, and delete.

7. Implement a CourseDAO class that implements the IDAO interface.

8. Implement a TeacherDAO class that implements the IDAO interface.

9. Implement a StudentDAO class that implements the IDAO interface.

10. Implement some tests for the DAO classes to make sure that they work. Just do it in the Main class. No need for building a real integration test.

11. Implement some JPQL queries to get data from the database. Be creative and try to get data from the database in different ways:

    • a) Get all students that are attending a specific course
    • b) Get all courses that a specific student is attending
    • c) Get all courses that a specific teacher is teaching
    • d) Get all students that are attending a course that a specific teacher is teaching