Spring Data JPA CrudRepository - findById() Method

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In this tutorial, we will learn how to use the Spring Data CrudRepository interface provided the findById() method with an example. 

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findById() Method Overview

As the name depicts, the findById() method allows us to get or retrieve an entity based on a given id (primary key) from the DB. 

It belongs to the CrudRepository interface defined by Spring Data.

The findById() method returns Optional of type Entity.

Maven Dependencies

Add the following maven dependencies to your Spring Boot project:
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>

		<dependency>
			<groupId>com.mysql</groupId>
			<artifactId>mysql-connector-j</artifactId>
			<scope>runtime</scope>
		</dependency>

Product Entity

Let's first create a Product entity that we are going to use to save and retrieve to/from the database:

package net.javaguides.springdatajpacourse.entity;

import org.hibernate.annotations.CreationTimestamp;
import org.hibernate.annotations.UpdateTimestamp;

import jakarta.persistence.*;
import java.math.BigDecimal;
import java.util.Date;

@Entity
@Table(name="products")
public class Product {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

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

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

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

    @Column(name = "price")
    private BigDecimal price;

    @Column(name = "image_url")
    private String imageUrl;

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

    @Column(name = "date_created")
    @CreationTimestamp
    private Date dateCreated;

    @Column(name = "last_updated")
    @UpdateTimestamp
    private Date lastUpdated;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDescription() {
        return description;
    }

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

    public BigDecimal getPrice() {
        return price;
    }

    public void setPrice(BigDecimal price) {
        this.price = price;
    }

    public String getImageUrl() {
        return imageUrl;
    }

    public void setImageUrl(String imageUrl) {
        this.imageUrl = imageUrl;
    }

    public boolean isActive() {
        return active;
    }

    public void setActive(boolean active) {
        this.active = active;
    }

    public Date getDateCreated() {
        return dateCreated;
    }

    public void setDateCreated(Date dateCreated) {
        this.dateCreated = dateCreated;
    }

    public Date getLastUpdated() {
        return lastUpdated;
    }

    public void setLastUpdated(Date lastUpdated) {
        this.lastUpdated = lastUpdated;
    }

    @Override
    public String toString() {
        return "Product{" +
                "id=" + id +
                ", sku='" + sku + '\'' +
                ", name='" + name + '\'' +
                ", description='" + description + '\'' +
                ", price=" + price +
                ", imageUrl='" + imageUrl + '\'' +
                ", active=" + active +
                ", dateCreated=" + dateCreated +
                ", lastUpdated=" + lastUpdated +
                '}';
    }
}

ProductRepository

Let's create ProductRepository which extends the CrudRepository interface. As we know that CrudRepository interface provides the findById() method so our ProductRepository interface should extend to the CrudRepository interface to get all its methods:

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

public interface ProductRepository extends CrudRepository<Product, Long> {

}

Configure MySQL and Hibernate Properties

Let's use the MySQL database to store and retrieve the data in this example and we gonna use Hibernate properties to create and drop tables.

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

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

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

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 ecommerce database before running the Spring boot application.
Also, change the MySQL username and password as per your MySQL installation on your machine.

Testing findById() Method

In order to test the findById() method, we gonna use CommandLineRunner.run() method to execute the testing code while the Spring boot application startup: 
import net.javaguides.springdatajpacourse.entity.Product;
import net.javaguides.springdatajpacourse.repository.ProductRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.math.BigDecimal;
import java.util.Date;
import java.util.List;

@SpringBootApplication
public class SpringDataJpaCourseApplication implements CommandLineRunner{

	public static void main(String[] args) throws Exception {
		SpringApplication.run(SpringDataJpaCourseApplication.class, args);
	}

	@Autowired
	private ProductRepository productRepository;

	@Override
	public void run(String... args) throws Exception {
		Product product = new Product();
        product.setName("product 1");
        product.setDescription("product 1 desc");
        product.setPrice(new BigDecimal(100));
        product.setDateCreated(new Date());
        product.setLastUpdated(new Date());
        product.setSku("product 1 sku");
        product.setActive(true);
        product.setImageUrl("product1.png");

        // save the product
        productRepository.save(product);

        // get product by id
        Product savedProduct = productRepository.findById(product.getId()).get();
        System.out.println(savedProduct);
	}
}

After finishing the Spring boot application, you can able to see Hibernate-generated SQL statements in a console:
Hibernate: 
    insert 
    into
        products
        (active, date_created, description, image_url, last_updated, name, price, sku) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: 
    select
        product0_.id as id1_0_0_,
        product0_.active as active2_0_0_,
        product0_.date_created as date_cre3_0_0_,
        product0_.description as descript4_0_0_,
        product0_.image_url as image_ur5_0_0_,
        product0_.last_updated as last_upd6_0_0_,
        product0_.name as name7_0_0_,
        product0_.price as price8_0_0_,
        product0_.sku as sku9_0_0_ 
    from
        products product0_ 
    where
        product0_.id=?
INSERT SQL statement to save the entity:
    insert 
    into
        products
        (active, date_created, description, image_url, last_updated, name, price, sku) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?)
SELECT SQL statement get entity by id:

    select
        product0_.id as id1_0_0_,
        product0_.active as active2_0_0_,
        product0_.date_created as date_cre3_0_0_,
        product0_.description as descript4_0_0_,
        product0_.image_url as image_ur5_0_0_,
        product0_.last_updated as last_upd6_0_0_,
        product0_.name as name7_0_0_,
        product0_.price as price8_0_0_,
        product0_.sku as sku9_0_0_ 
    from
        products product0_ 
    where
        product0_.id=?

Related Spring Data CrudRepository Tutorials

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