Spring Boot JPA + H2 example: Build a CRUD Rest APIs

In this tutorial, we’re gonna build a Spring Boot Rest CRUD API example with Maven that use Spring Data JPA to interact with H2 database. You’ll know:

• How to configure Spring Data, JPA, Hibernate to work with Database
• How to define Data Models and Repository interfaces
• Way to create Spring Rest Controller to process HTTP requests
• Way to use Spring Data JPA to interact with H2 Database

Fullstack:
– Spring Boot Thymeleaf example
– 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
– Angular 15 + Spring Boot example
– React + Spring Boot example

JdbcTemplate instead:
Spring Boot JdbcTemplate example: CRUD Rest API

Reactive with R2DBC:
Spring Boot R2DBC + H2 example

Exception Handling:
– Spring Boot @ControllerAdvice & @ExceptionHandler example
– @RestControllerAdvice example in Spring Boot

Testing:
– Spring Boot Unit Test for JPA Repository
– Spring Boot Unit Test for Rest Controller

Associations:
– Spring Boot One To One example with JPA, Hibernate
– Spring Boot One To Many example with JPA, Hibernate
– Spring Boot Many to Many example with JPA, Hibernate

Using other databases:
– Spring JPA + SQL Server
– Spring JPA + PostgreSQL
– Spring JPA + MySQL
– Spring Data + MongoDB

Overview of Spring Boot JPA + H2 example

We will build a Spring Boot Rest Apis using Spring Data JPA with H2 Database for a Tutorial application in that:

• Each Tutorial has id, title, description, published status.
• Apis help to create, retrieve, update, delete Tutorials.
• Apis also support custom finder methods such as find by published status or by title.

These are APIs that we need to provide:

– We make CRUD operations & finder methods with Spring Data JPA’s JpaRepository.
– The database will be H2 Database (in memory or on disk) by configuring project dependency & datasource.

Technology

• Java 17 / 11 / 8
• Spring Boot 3 / 2 (with Spring Web MVC, 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. It will be autowired in TutorialController.
– TutorialController is a RestController which has request mapping methods for RESTful requests such as: getAllTutorials, createTutorial, updateTutorial, deleteTutorial, findByPublished…
– Configuration for Spring Datasource, JPA & Hibernate in application.properties.
– pom.xml contains dependencies for Spring Boot and H2 Database.

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-web</artifactId>
</dependency>

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

Configure Spring Boot, JPA, h2, Hibernate

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

spring.datasource.url=jdbc:h2:mem: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.h2.console.enabled=true
# default path: h2-console
spring.h2.console.path=/h2-ui

• 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.

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.jpa.h2.model;

import javax.persistence.*;
// import jakarta.persistence.*; // for Spring Boot 3

@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;
	}

	public long getId() {
		return id;
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public boolean isPublished() {
		return published;
	}

	public void setPublished(boolean isPublished) {
		this.published = isPublished;
	}

	@Override
	public String toString() {
		return "Tutorial [id=" + id + ", title=" + title + ", desc=" + description + ", published=" + published + "]";
	}

}

– @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.jpa.h2.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;

import com.bezkoder.spring.jpa.h2.model.Tutorial;

public interface TutorialRepository extends JpaRepository<Tutorial, Long> {
  List<Tutorial> findByPublished(boolean published);

  List<Tutorial> findByTitleContaining(String title);
}

Now we can use JpaRepository’s methods: save(), findOne(), findById(), findAll(), count(), delete(), deleteById()… without implementing these methods.

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

Create Spring Rest APIs Controller

Finally, we create a controller that provides APIs for creating, retrieving, updating, deleting and finding Tutorials.

controller/TutorialController.java

package com.bezkoder.spring.jpa.h2.controller;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.bezkoder.spring.jpa.h2.model.Tutorial;
import com.bezkoder.spring.jpa.h2.repository.TutorialRepository;

@CrossOrigin(origins = "http://localhost:8081")
@RestController
@RequestMapping("/api")
public class TutorialController {

	@Autowired
	TutorialRepository tutorialRepository;

	@GetMapping("/tutorials")
	public ResponseEntity<List<Tutorial>> getAllTutorials(@RequestParam(required = false) String title) {
		try {
			List<Tutorial> tutorials = new ArrayList<Tutorial>();

			if (title == null)
				tutorialRepository.findAll().forEach(tutorials::add);
			else
				tutorialRepository.findByTitleContaining(title).forEach(tutorials::add);

			if (tutorials.isEmpty()) {
				return new ResponseEntity<>(HttpStatus.NO_CONTENT);
			}

			return new ResponseEntity<>(tutorials, HttpStatus.OK);
		} catch (Exception e) {
			return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR);
		}
	}

	@GetMapping("/tutorials/{id}")
	public ResponseEntity<Tutorial> getTutorialById(@PathVariable("id") long id) {
		Optional<Tutorial> tutorialData = tutorialRepository.findById(id);

		if (tutorialData.isPresent()) {
			return new ResponseEntity<>(tutorialData.get(), HttpStatus.OK);
		} else {
			return new ResponseEntity<>(HttpStatus.NOT_FOUND);
		}
	}

	@PostMapping("/tutorials")
	public ResponseEntity<Tutorial> createTutorial(@RequestBody Tutorial tutorial) {
		try {
			Tutorial _tutorial = tutorialRepository
					.save(new Tutorial(tutorial.getTitle(), tutorial.getDescription(), false));
			return new ResponseEntity<>(_tutorial, HttpStatus.CREATED);
		} catch (Exception e) {
			return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR);
		}
	}

	@PutMapping("/tutorials/{id}")
	public ResponseEntity<Tutorial> updateTutorial(@PathVariable("id") long id, @RequestBody Tutorial tutorial) {
		Optional<Tutorial> tutorialData = tutorialRepository.findById(id);

		if (tutorialData.isPresent()) {
			Tutorial _tutorial = tutorialData.get();
			_tutorial.setTitle(tutorial.getTitle());
			_tutorial.setDescription(tutorial.getDescription());
			_tutorial.setPublished(tutorial.isPublished());
			return new ResponseEntity<>(tutorialRepository.save(_tutorial), HttpStatus.OK);
		} else {
			return new ResponseEntity<>(HttpStatus.NOT_FOUND);
		}
	}

	@DeleteMapping("/tutorials/{id}")
	public ResponseEntity<HttpStatus> deleteTutorial(@PathVariable("id") long id) {
		try {
			tutorialRepository.deleteById(id);
			return new ResponseEntity<>(HttpStatus.NO_CONTENT);
		} catch (Exception e) {
			return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
		}
	}

	@DeleteMapping("/tutorials")
	public ResponseEntity<HttpStatus> deleteAllTutorials() {
		try {
			tutorialRepository.deleteAll();
			return new ResponseEntity<>(HttpStatus.NO_CONTENT);
		} catch (Exception e) {
			return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
		}

	}

	@GetMapping("/tutorials/published")
	public ResponseEntity<List<Tutorial>> findByPublished() {
		try {
			List<Tutorial> tutorials = tutorialRepository.findByPublished(true);

			if (tutorials.isEmpty()) {
				return new ResponseEntity<>(HttpStatus.NO_CONTENT);
			}
			return new ResponseEntity<>(tutorials, HttpStatus.OK);
		} catch (Exception e) {
			return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
		}
	}

}

– @CrossOrigin is for configuring allowed origins.
– @RestController annotation is used to define a controller and to indicate that the return value of the methods should be be bound to the web response body.
– @RequestMapping("/api") declares that all Apis’ url in the controller will start with /api.
– We use @Autowired to inject TutorialRepository bean to local variable.

You can find way to write Unit test for this Controller at:
Spring Boot Unit Test for Rest Controller

Run & Test

Run Spring Boot application with command: mvn spring-boot:run.

tutorials table will be automatically generated in Database.

Let’s open H2 console with url: http://localhost:8080/h2-ui:

– For In-memory database:

– For on Disk database:

Click on Connect button, then check H2 database, you can see things like this:

Create some Tutorials:

H2 database tutorials table after that:

Update some Tutorials:

The table data is changed:

Retrieve all Tutorials:

Retrieve a Tutorial by Id:

Find all published Tutorials:

Find all Tutorials which title contains string ‘ot’:

Delete a Tutorial:

Delete all Tutorials:

H2 database table is clean now:

You can also test this Spring Boot App with Client in one of these posts:

• Simple HTTP Client using Axios
• Simple HTTP Client using Fetch API
• Angular 8 CRUD Application example with Web API
• Angular 10 CRUD Application example with Web API
• Angular 11 CRUD Application example with Web API
• Angular 12 CRUD Application example with Web API
• Angular 13 CRUD Application example with Web API
• Angular 14 CRUD Application example with Web API
• Angular 15 CRUD Application example with Web API
• Vue 2 CRUD Application with Vue Router & Axios
• Vue 3 CRUD Application with Axios & Vue Router
• React CRUD example with Axios
• React Redux CRUD example

Conclusion

Today we’ve built a Rest CRUD API using Spring Boot, Spring Data JPA working with H2 Database example.

We also see that JpaRepository supports a great way to make CRUD operations and custom finder methods without need of boilerplate code.

Custom query with @Query annotation:
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:
– Spring Boot Unit Test for JPA Repository
– Spring Boot Unit Test for Rest Controller

Happy learning! See you again.

Further Reading

• Secure Spring Boot App with Spring Security & JWT Authentication
• Spring Data JPA Reference Documentation

Fullstack CRUD App:
– Spring Boot Thymeleaf example
– 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
– Angular 15 + Spring Boot example
– React + Spring Boot example

More Practice:
– Secure Spring Boot App with Spring Security & JWT Authentication
– Spring Boot Rest XML example – Web service with XML Response
– Spring Boot Multipart File upload example
– Spring Boot Pagination and Sorting example

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

Source Code

You can find the complete source code for this tutorial on Github.

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

Validation:
Validate Request Body in Spring Boot

Using other databases:
– Spring JPA + SQL Server
– Spring JPA + PostgreSQL
– Spring JPA + MySQL
– Spring Data + MongoDB

Or JdbcTemplate instead:
Spring Boot JdbcTemplate example: CRUD Rest API

Reactive with R2DBC:
Spring Boot R2DBC + H2 example

Documentation: Spring Boot + Swagger 3 example (with OpenAPI 3)
Caching: Spring Boot Redis Cache example