spring-data-jpa-relationships

The goal of this project is to study the JPA relationships: one-to-one, one-to-many / many-to-one, and many-to-many.

Proof-of-Concepts & Articles

On ivangfr.github.io, I have compiled my Proof-of-Concepts (PoCs) and articles. You can easily search for the technology you are interested in by using the filter. Who knows, perhaps I have already implemented a PoC or written an article about what you are looking for.

Additional Readings

• [Medium] Understanding Relationships in JPA: Introduction
• [Medium] Understanding Relationships in JPA: One-to-One with Simple Primary Key
• [Medium] Understanding Relationships in JPA: One-to-One with Shared Primary Key
• [Medium] Understanding Relationships in JPA: One-to-Many with Simple Primary Key
• [Medium] Understanding Relationships in JPA: One-to-Many with Composite Primary Key
• [Medium] Understanding Relationships in JPA: Many-to-Many with Simple Primary Key
• [Medium] Understanding Relationships in JPA: Many-to-Many with Simple Primary Key and Extra Column
• [Medium] Understanding Relationships in JPA: Many-to-Many with Composite Primary Key and Extra Column
• [Medium] Mastering JPA Relationships: Practical Examples of Bidirectional Associations

Prerequisites

• Java 21+
• Some containerization tool Docker, Podman, etc.

Start Environment

In a terminal and inside the spring-data-jpa-relationships root folder, run the following command:

docker compose up -d

Running application using Maven

In a terminal and inside the spring-data-jpa-relationships root folder, run the command below:

./mvnw clean spring-boot:run

Once the application is running, you can access its Swagger website at http://localhost:8080/swagger-ui.html.

Useful Commands

• Postgres

  docker exec -it postgres psql -U postgres -d jparelationshipsdb
  \d persons
  select * from persons;
  

  Type exit to exit

Shutdown

• To stop the application, go to the terminal where it is running and press Ctrl+C;
• To stop and remove docker compose containers, network and volumes, go to a terminal and, inside the spring-data-jpa-relationships root folder, run the following command:

  docker compose down -v
  

Running Tests

In a terminal and inside the spring-data-jpa-relationships root folder, run the following command:

./mvnw clean test

JPA relationships

One-to-One with Simple Primary Key

[Medium]: Understanding Relationships in JPA: One-to-One with Simple Primary Key

One-to-One with Shared Primary Key

[Medium] Understanding Relationships in JPA: One-to-One with Shared Primary Key

One-to-Many with Simple Primary Key

[Medium] Understanding Relationships in JPA: One-to-Many with Simple Primary Key

One-to-Many with Composite Primary Key

[Medium] Understanding Relationships in JPA: One-to-Many with Composite Primary Key

Many-to-Many with Simple Primary Key

[Medium] Understanding Relationships in JPA: Many-to-Many with Simple Primary Key

Many-to-Many with Simple Primary Key and Extra Column

[Medium] Understanding Relationships in JPA: Many-to-Many with Simple Primary Key and Extra Column

Many-to-Many with Composite Primary Key and Extra Column

[Medium] Understanding Relationships in JPA: Many-to-Many with Composite Primary Key and Extra Column

References

One-to-One

• https://vladmihalcea.com/the-best-way-to-map-a-onetoone-relationship-with-jpa-and-hibernate
• https://www.callicoder.com/hibernate-spring-boot-jpa-one-to-one-mapping-example/

One-to-Many / Many-to-One

• https://vladmihalcea.com/the-best-way-to-map-a-onetomany-association-with-jpa-and-hibernate
• https://www.callicoder.com/hibernate-spring-boot-jpa-one-to-many-mapping-example/

Many-to-Many

• https://vladmihalcea.com/the-best-way-to-use-the-manytomany-annotation-with-jpa-and-hibernate
• https://www.callicoder.com/hibernate-spring-boot-jpa-many-to-many-mapping-example/