In this tutorial, I will show you how to implement Spring JPA One-To-One unidirectional mapping with Hibernate in a Spring Boot example using
@OneToOne annotation. You'll know:
- How to configure Spring Data, JPA, Hibernate to work with Database
- How to define Data Models and Repository interfaces for JPA One-To-One relationship
- Way to use Spring JPA to interact with Database for One-To-One association
- Way to create Spring Rest Controller to process HTTP requests
Full article at: https://www.bezkoder.com/jpa-one-to-one/
Appropriate way to implement JPA/Hibernate One To One mapping
In a relational database, a One-to-One relationship between table A and table B indicates that one row in table A links to only one row in table B, and vice versa.
For example, you need to design data model for a Tutorial Blog in which One Tutorial has corresponding Details (the Date Time it was created on, the author it was created by). So this is a One-to-One association.
You can use a Join Table (with @JoinTable annotation). It stores the primary key values from both entities in a NEW table.
Another way is to use Shared Primary Key with the Foreign Key is located in the tutorial_details table. Tutorial entity is the parent, and the Tutorial Details is the child.
You can map the child entity with the parent using JPA/Hibernate @OneToOne annotation. And in this case, only the children-side defines the relationship. We call it unidirectional One-to-One association.
Now look at the tutorial_details table that contains a Primary Key column (
id) and a Foreign Key column (
tutorial_id). You can see that we really need only one tutorial_details (child) row associated with a tutorial (parent) row, and the child data is hardly used in other relationships. So we can omit the child's
JPA One To One example
We're gonna create a Spring project from scratch, then we implement JPA/Hibernate One to One Unidirectional Mapping with
tutorial_details table as following:
We also write Rest Apis to perform CRUD operations on the Details entities.
These are APIs that we need to provide:
|POST||/api/tutorials/:id/details||create new Details for a Tutorial|
|GET||/api/details/:id||retrieve Details by
|GET||/api/tutorials/:id/details||retrieve Details of a Tutorial|
|PUT||/api/details/:id||update Details by
|PUT||/api/tutorials/:id/details||update Details of a Tutorial|
|DELETE||/api/details/:id||delete Details by
|DELETE||/api/tutorials/:id/details||delete Details of a Tutorial|
|DELETE||/api/tutorials/:id||delete a Tutorial (and its Details)|
Assume that we've had tutorials table like this:
Here are the example requests:
- Create new Details entity: POST
tutorial_details table after that:
- Retrieve Details of specific Tutorial: GET
- Update Details of specific Tutorial: PUT
- Delete Details of specific Tutorial: DELETE
Check the tutorial_details table, row with tutorial_id=1 were deleted:
- Delete a Tutorial: DELETE
Tutorial (id=3) and its Details were deleted:
Let's build our Spring Boot Data JPA One to One example.
Spring Boot One to One example
- Java 8
- Spring Boot 2.7.2 (with Spring Web MVC, Spring Data JPA)
- Maven 3.8.1
Let me explain it briefly.
TutorialDetails data model class correspond to entity and table tutorials, tutorial_details.
TutorialDetailsRepository are interfaces that extends JpaRepository for CRUD methods and custom finder methods. It will be autowired in
TutorialDetailsController are RestControllers which has request mapping methods for RESTful CRUD API requests.
– Configuration for Spring Datasource, JPA & Hibernate in application.properties.
– pom.xml contains dependencies for Spring Boot and MySQL/PostgreSQL/H2 database.
– About exception package, to keep this post straightforward, I won't explain it. For more details, you can read following tutorial:
@RestControllerAdvice example in Spring Boot
Step by step and Github source code can be found at:
Custom query with
Spring JPA @Query example: Custom query in Spring Boot
If you want to add Pagination to this Spring project, you can find the instruction at:
Spring Boot Pagination & Filter example | Spring JPA, Pageable
To sort/order by multiple fields:
Spring Data JPA Sort/Order by multiple Columns | Spring Boot
Handle Exception for this Rest APIs is necessary:
- Spring Boot @ControllerAdvice & @ExceptionHandler example
- @RestControllerAdvice example in Spring Boot
Or way to write Unit Test for the JPA Repository:
Spring Boot Unit Test for JPA Repositiory with @DataJpaTest
You can also know:
- how to deploy this Spring Boot App on AWS (for free) with this tutorial.
- dockerize with Docker Compose: Spring Boot and MySQL example
- way to upload an Excel file and store the data in MySQL database with this post
- upload CSV file and store the data in MySQL with this post.
- Secure Spring Boot App with Spring Security & JWT Authentication
- Spring Data JPA Reference Documentation
- Spring Boot Pagination and Sorting example
Fullstack CRUD App:
- Vue + Spring Boot example
- Angular 8 + Spring Boot example
- Angular 10 + Spring Boot example
- Angular 11 + Spring Boot example
- Angular 12 + Spring Boot example
- Angular 13 + Spring Boot example
- Angular 14 + Spring Boot example
- React + Spring Boot example
You can find the complete source code for this tutorial on Github.
One-to-Many: JPA One To Many example with Hibernate and Spring Boot
Many-to-Many: JPA Many to Many example with Hibernate in Spring Boot
You can apply this implementation in following tutorials:
- Spring JPA + H2 example
- Spring JPA + MySQL example
- Spring JPA + PostgreSQL example
- Spring JPA + Oracle example
- Spring JPA + SQL Server example
More Derived queries at:
JPA Repository query example in Spring Boot