How to use Spring Data JPA in Spring Boot Project

In the previous tutorial, we have seen what is Spring Data JPA?

In this quick tutorial, we will learn how to use the Spring Data JPA repository in the Spring Boot application.

Prerequisites

In order to use Spring Data JPA in the Spring boot application, first, you need to add the below dependency to your Spring boot application:

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

Next, you need to configure the database in your Spring boot application.

For example, if you are using MySQL database, then add MySQL JDBC driver dependency:

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>

Also, you need to configure MySQL details in the application.properties file to connect Spring boot application with MySQL database:

Open the application.properties file and add the following configuration to it:

spring.datasource.url=jdbc:mysql://localhost:3306/demo?useSSL=false
spring.datasource.username=root
spring.datasource.password=Mysql@123

spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect

spring.jpa.hibernate.ddl-auto = create-drop

spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true
Make sure that you will create a demo database before running the Spring boot application.

Also, change the MySQL username and password as per your MySQL installation on your machine.

Steps to Use Spring Data JPA in Spring Boot Project

Once you have set up a database connection with your Spring boot application then here are the steps to use the Spring Data JPA repository.

1. Create a repository interface and extend it to the JpaRepository interface

2. Add custom query methods to the created repository interface (if we need them)

3. Inject the repository interface to another component and use the implementation that is provided automatically by Spring Data JPA.

1. Create a repository interface and extend it to the JpaRepository interface

Consider we have a Product entity. Now let's create a ProductRepository that extends JpaRepository and add the following code to it:
import java.util.List;

import net.javaguides.springdatajpacourse.entity.Product;
import org.springframework.data.jpa.repository.JpaRepository;

public interface ProductRepository extends JpaRepository<Product, Long> {

}

2. Add custom query methods to the created repository interface (if we need them)

Spring Data JPA query methods are the most powerful methods, we can create query methods to select the records from the database without writing SQL queries. Behind the scenes, Spring Data JPA will create SQL queries based on the query method and execute the query for us.

For example:
import com.springboot.crud.example.entity.Product;
import org.springframework.data.jpa.repository.JpaRepository;

public interface ProductRepository extends JpaRepository<Product,Integer> {
    Product findByName(String name);
}
This is a query method:
Product findByName(String name);

3. Inject the repository interface to another component and use the implementation that is provided automatically by Spring Data JPA

We can create a ProductService class and then inject ProductRepository using @Autowired annotation to use it's methods:
import com.springboot.crud.example.entity.Product;
import com.springboot.crud.example.repository.ProductRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class ProductService {
    @Autowired
    private ProductRepository repository;

    public Product saveProduct(Product product) {
        return repository.save(product);
    }

    public List<Product> saveProducts(List<Product> products) {
        return repository.saveAll(products);
    }

    public List<Product> getProducts() {
        return repository.findAll();
    }

    public Product getProductById(int id) {
        return repository.findById(id).orElse(null);
    }

    public Product getProductByName(String name) {
        return repository.findByName(name);
    }

    public String deleteProduct(int id) {
        repository.deleteById(id);
        return "product removed !! " + id;
    }

    public Product updateProduct(Product product) {
        Product existingProduct = repository.findById(product.getId()).orElse(null);
        existingProduct.setName(product.getName());
        existingProduct.setQuantity(product.getQuantity());
        existingProduct.setPrice(product.getPrice());
        return repository.save(existingProduct);
    }
}
Well, these are the three simple steps to use the Spring Data JPA repository

Complete Example

Let's create a complete end-to-end Spring boot project to demonstrate the usage of Spring Data JPA.

1. Create Spring Boot Project

We’ll use Spring initializr web tool to bootstrap our application. 

Go to http://start.spring.io

Select Java in the language section.

Enter Artifact as spring-boot-crud-example

Add WebLombokJPA, and MySQL dependencies.

Click Generate to generate and download the project.

Once the project is generated, unzip it and import it into your favorite IDE.

2. Maven Dependencies

Open the pom.xml file and confirm below dependencies are present:

		<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>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<scope>runtime</scope>
		</dependency>
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>

3. Configure MySQL Database

Let's first create a database named "demo" in the MySQL server.

Now, let's configure MySQL database URL, username, and password so that Spring Boot can create a Data source.

Open src/main/resources/application.properties file and add the following properties to it -

spring.datasource.url = jdbc:mysql://localhost:3306/demo?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&useSSL=false
spring.datasource.username = root
spring.datasource.password = root
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.hibernate.ddl-auto = update
Change spring.datasource.username and spring.datasource.password as per your MySQL installation.

Note that, I’ve set spring.jpa.hibernate.ddl-auto property to update. This property updates the database schema whenever you create or modify the domain models in your application.

4. Creating Model Layer

Create a Product class with the following content into it:

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "PRODUCT_TBL")
public class Product {

    @Id
    @GeneratedValue
    private int id;
    private String name;
    private int quantity;
    private double price;
}

5. Create Repository Layer

Create ProductRepository interface with the following content into it:
import com.springboot.crud.example.entity.Product;
import org.springframework.data.jpa.repository.JpaRepository;

public interface ProductRepository extends JpaRepository<Product,Integer> {
    Product findByName(String name);
}

6. Create Service Layer

Create a ProductService class with the following content into it:
import com.springboot.crud.example.entity.Product;
import com.springboot.crud.example.repository.ProductRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class ProductService {
    @Autowired
    private ProductRepository repository;

    public Product saveProduct(Product product) {
        return repository.save(product);
    }

    public List<Product> saveProducts(List<Product> products) {
        return repository.saveAll(products);
    }

    public List<Product> getProducts() {
        return repository.findAll();
    }

    public Product getProductById(int id) {
        return repository.findById(id).orElse(null);
    }

    public Product getProductByName(String name) {
        return repository.findByName(name);
    }

    public String deleteProduct(int id) {
        repository.deleteById(id);
        return "product removed !! " + id;
    }

    public Product updateProduct(Product product) {
        Product existingProduct = repository.findById(product.getId()).orElse(null);
        existingProduct.setName(product.getName());
        existingProduct.setQuantity(product.getQuantity());
        existingProduct.setPrice(product.getPrice());
        return repository.save(existingProduct);
    }
}

7. Create Controller Layer

Create ProductController class with the following content into it:
import com.springboot.crud.example.entity.Product;
import com.springboot.crud.example.service.ProductService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
public class ProductController {

    @Autowired
    private ProductService service;

    @PostMapping("/addProduct")
    public Product addProduct(@RequestBody Product product) {
        return service.saveProduct(product);
    }

    @PostMapping("/addProducts")
    public List<Product> addProducts(@RequestBody List<Product> products) {
        return service.saveProducts(products);
    }

    @GetMapping("/products")
    public List<Product> findAllProducts() {
        return service.getProducts();
    }

    @GetMapping("/productById/{id}")
    public Product findProductById(@PathVariable int id) {
        return service.getProductById(id);
    }

    @GetMapping("/product/{name}")
    public Product findProductByName(@PathVariable String name) {
        return service.getProductByName(name);
    }

    @PutMapping("/update")
    public Product updateProduct(@RequestBody Product product) {
        return service.updateProduct(product);
    }

    @DeleteMapping("/delete/{id}")
    public String deleteProduct(@PathVariable int id) {
        return service.deleteProduct(id);
    }
}

8. Run Spring Boot Application

We’ve successfully built all the APIs for our application. Let’s now run the app and test the APIs.

Just go to the root directory of the application and type the following command to run it -

$ mvn spring-boot:run

The application will start at Spring Boot’s default tomcat port 8080.

Conclusion

In this tutorial, we have seen how to use the Spring Data JPA repository interface in the Spring boot project. We have also created a complete example to demonstrate the usage of Spring data JPA end to end.

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