Implementing Relationships using JPA in MediCare

Business Scenario

The objective of this lab is to implement relationships between multiple modules in a Spring Boot application using JPA. This helps in connecting entities such as User, Doctor, Appointment, Order, and CartItem in a structured and relational way.

Manager:
Our healthcare application has users, doctors, appointments, and medicine orders. How will we connect all this data?

Full Stack Developer:
Using JPA Relationships (@OneToMany) to connect Users, Doctors, Appointments, Orders, CartItems, and Medicines efficiently.

Manager:
Why are relationships important?

Full Stack Developer:
They reduce data duplication, maintain foreign key integrity, and make the database structure realistic and easier to manage using annotations like @OneToMany, @ManyToOne, and @JoinColumn.

Manager:
Great, let’s implement it.

Pre-Lab Preparation

Hibernate & Spring Data JPA: Model to Repository
Service Layer: Concepts & Implementation
Controller Layer: HTTP Handling & CRUD APIs
Validation & Exception Handling in APIs
Entity Relationships & Advanced JPA Features

Task 1: Understanding BRD

Open existing Spring Boot project

Ensure dependencies:

Spring Web
Spring Data JPA
MySQL Driver

Update Entity Classes

Modify entities to include relationships.

Example: Appointment Entity

@ManyToOne
@JoinColumn(name = "user_id")
private User user;

@ManyToOne
@JoinColumn(name = "doctor_id")
private Doctor doctor;

Add OneToMany Mapping

Example: User Entity

@OneToMany(mappedBy = "user")
private List<Appointment> appointments;

Repeat for Other Entities

Apply relationships in:

Doctor → Appointment
Order → CartItem
Medicine → CartItem

Add Constructors and Getter/Setter

Ensure each entity contains:

Default constructor
Parameterized constructor
Getter and Setter methods
Complete entity class

Configure Database

spring.datasource.url=jdbc:mysql://localhost:3306/medicare
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

Run Application

(Run project as Spring Boot App) , (Verify successful startup)

Verify Tables and Relationships

Open MySQL
Check tables:
- appointments table should contain:
  - user_id
  - doctor_id
cart_items table should contain:
- order_id
- medicine_id

Test API using Postman

Example: Appointment POST

{
 "appointmentDate": "2026-06-10",
 "timeSlot": "10:00 AM",
 "reason": "Fever",
 "status": "BOOKED",
 "paymentStatus": "PENDING",
 "user": { "id": 1 },
 "doctor": { "id": 2 }
}