Tien Nguyen

Posted on Nov 21, 2023

Spring Data REST example

#webdev #springboot #tutorial #java

In this tutorial, we're gonna build a Spring Data REST example in Spring Boot CRUD REST API with Maven that uses Spring Data JPA to interact with H2 database without having to manually implement controller and handling HTTP requests. You'll know:

How to configure Spring Data REST, JPA, Hibernate to work with Database
How to define Data Models and Repository interfaces
Way to use Spring Data JPA to interact with H2 Database
How to check CRUD operations with Postman

Spring Data REST

Purpose: Spring Data REST builds on top of Spring Data repositories and exposes them as RESTful services. It automates the process of exposing JPA repositories as RESTful endpoints.
Features:
- Automatic generation of RESTful APIs for Spring Data repositories.
- Supports CRUD operations over HTTP (GET, POST, PUT, DELETE) for entities.
- Follows HATEOAS (Hypermedia as the Engine of Application State) principles, providing discoverable APIs.
- Customization of endpoints and response formats.
Usage: Spring Data REST is used when you want to quickly expose your Spring Data JPA repositories as RESTful services without having to manually implement controllers and handling HTTP requests. It's useful for rapidly building APIs over your data model.

Spring Data REST example

We will build a Spring Boot Data REST example for a Tutorial application in that:

Each Tutorial has id, title, description, published status.
We can create, retrieve, update, delete Tutorials.
We have custom finder methods such as find by published status or by title.

These are REST APIs that we provide:

Methods	Urls	Actions
POST	/api/tutorials	create new Tutorial
GET	/api/tutorials	retrieve all Tutorials
GET	/api/tutorials/:id	retrieve a Tutorial by `:id`
PUT	/api/tutorials/:id	update a Tutorial by `:id`
DELETE	/api/tutorials/:id	delete a Tutorial by `:id`

We also have APIs for:

filtering all published/unpublished Tutorials:
GET /api/tutorials/search/findByPublished?published=[status]
filtering all Tutorials which title contains keyword
/api/tutorials/search/findByTitleContainingIgnoreCase?title=[keyword]

Technology

Java 17 / 11 / 8
Spring Boot 3 / 2 (with Spring Data REST, Spring Data JPA)
H2 Database
Maven

Project Structure

Let me explain it briefly.

– Tutorial data model class corresponds to entity and table tutorials.
– TutorialRepository is an interface that extends JpaRepository for CRUD methods and custom finder methods.
– Configuration for Spring Data REST, Datasource, JPA & Hibernate in application.properties.
– pom.xml contains dependencies for Spring Boot and H2.

We can improve the example by adding Comments for each Tutorial. It is the One-to-Many Relationship and I write a tutorial for this at:
Spring Boot One To Many example with JPA, Hibernate

Or add Tags with Many-to-Many Relationship:
Spring Boot Many to Many example with JPA, Hibernate

Create & Setup Spring Boot project

Use Spring web tool or your development tool (Spring Tool Suite, Eclipse, Intellij) to create a Spring Boot project.

Then open pom.xml and add these dependencies:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-rest</artifactId>
</dependency>

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

Configure Spring Data REST, JPA, h2, Hibernate

Under src/main/resources folder, open application.properties and write these lines.

spring.data.rest.basePath=api

spring.h2.console.enabled=true
# default path: h2-console
spring.h2.console.path=/h2-ui

spring.datasource.url=jdbc:h2:file:./testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=

spring.jpa.show-sql=true
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.H2Dialect
spring.jpa.hibernate.ddl-auto= update

spring.data.rest.basePath: the root URI for Spring Data REST
spring.datasource.url: jdbc:h2:mem:[database-name] for In-memory database and jdbc:h2:file:[path/database-name] for disk-based database.
spring.datasource.username & spring.datasource.password properties are the same as your database installation.
Spring Boot uses Hibernate for JPA implementation, we configure H2Dialect for H2 Database
spring.jpa.hibernate.ddl-auto is used for database initialization. We set the value to update value so that a table will be created in the database automatically corresponding to defined data model. Any change to the model will also trigger an update to the table. For production, this property should be validate.
spring.h2.console.enabled=true tells the Spring to start H2 Database administration tool and you can access this tool on the browser: http://localhost:8080/h2-console.
spring.h2.console.path=/h2-ui is for H2 console's url, so the default url http://localhost:8080/h2-console will change to http://localhost:8080/h2-ui.

You can also alter the following Spring Data REST properties (starting with spring.data.rest.):

defaultPageSize: change the default for the number of items served in a single page.
maxPageSize: change the maximum number of items in a single page.
pageParamName: change the name of the query parameter for selecting pages.
limitParamName: change the name of the query parameter for the number of items to show in a page.
sortParamName: change the name of the query parameter for sorting.
defaultMediaType: change the default media type to use when none is specified.
returnBodyOnCreate: change whether a body should be returned when creating a new entity.
returnBodyOnUpdate: change whether a body should be returned when updating an entity.

Define Data Model

Our Data model is Tutorial with four fields: id, title, description, published.
In model package, we define Tutorial class.

model/Tutorial.java

package com.bezkoder.spring.data.rest.model;

import jakarta.persistence.*;

@Entity
@Table(name = "tutorials")
public class Tutorial {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private long id;

  @Column(name = "title")
  private String title;

  @Column(name = "description")
  private String description;

  @Column(name = "published")
  private boolean published;

  public Tutorial() {

  }

  public Tutorial(String title, String description, boolean published) {
    this.title = title;
    this.description = description;
    this.published = published;
  }

  // getters and setters...

}

@Entity annotation indicates that the class is a persistent Java class.
@Table annotation provides the table that maps this entity.
@Id annotation is for the primary key.
@GeneratedValue annotation is used to define generation strategy for the primary key. GenerationType.AUTO means Auto Increment field.
@Column annotation is used to define the column in database that maps annotated field.

Create Repository Interface

Let's create a repository to interact with Tutorials from the database.
In repository package, create TutorialRepository interface that extends JpaRepository.

repository/TutorialRepository.java

package com.bezkoder.spring.data.rest.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;
import org.springframework.web.bind.annotation.CrossOrigin;

import com.bezkoder.spring.data.rest.model.Tutorial;

@RepositoryRestResource(path="tutorials")
public interface TutorialRepository extends JpaRepository<Tutorial, Long> {
  List<Tutorial> findByPublished(boolean published);

  List<Tutorial> findByTitleContainingIgnoreCase(String title);
}

To expose the repository as a RESTful resource, you annotate the repository interface with @RepositoryRestResource. This annotation allows you to customize the RESTful endpoints and behavior, and path defines the base URI path for the resource.

We also define custom finder methods:

findByPublished(): returns all Tutorials with published having value as input published.
findByTitleContaining(): returns all Tutorials which title contains input title.

The implementation is plugged in by Spring Data JPA automatically.

More Derived queries at:
JPA Repository query example in Spring Boot

Custom query with @Query annotation:
Spring JPA @Query example: Custom query in Spring Boot

You can modify this Repository:

to work with Pagination, the instruction can be found at: Spring Boot Pagination & Filter example | Spring JPA, Pageable
or to sort/order by multiple fields with the tutorial: Spring Data JPA Sort/Order by multiple Columns | Spring Boot

You also find way to write Unit Test for this JPA Repository at:
Spring Boot Unit Test for JPA Repository with @DataJpaTest

Configure CORS in Spring Data REST

We add a @CrossOrigin annotation to the repository interface to enable CORS for the whole TutorialRepository repository.

By default, @CrossOrigin allows all origins and HTTP methods.

repository/TutorialRepository.java

// ...
import org.springframework.web.bind.annotation.CrossOrigin;

@CrossOrigin
@RepositoryRestResource(path="tutorials")
public interface TutorialRepository extends JpaRepository<Tutorial, Long> {
  // ...
}

We can provide one origin, restricted to several HTTP methods with a specific max age.

@CrossOrigin(origins = "http://yourdomain.example",
  methods = { RequestMethod.GET, RequestMethod.POST, RequestMethod.DELETE },
  maxAge = 3600)
@RepositoryRestResource(path="tutorials")
public interface TutorialRepository extends JpaRepository<Tutorial, Long> {
  // ...
}