Spring Data JPA - count() Method Example

In this source code example, we will demonstrate how to use the count() method in Spring Data JPA to count a number of records in a database table.

As the name depicts, the count() method allows us to count the number of records that exist in a database table. 

In this example, we will use the Product entity to save and retrieve records to/from the MySQL database.

Maven Dependencies

First, you need to add the below dependencies to your Spring boot project:

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

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

Create Product Entity

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

package net.javaguides.springdatajpacourse.entity;

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

import javax.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;

    // getter and setter methods

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

public interface ProductRepository extends JpaRepository<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/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.

Testing count() Method

Let's write a JUnit test to test count() method:

import net.javaguides.springdatajpacourse.entity.Product;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureTestDatabase;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;

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

@DataJpaTest
@AutoConfigureTestDatabase(replace= AutoConfigureTestDatabase.Replace.NONE)
class ProductRepositoryTest {

    @Autowired
    private ProductRepository productRepository;

    protected Product getProduct1(){
        Product product = new Product();
        product.setName("product 1");
        product.setDescription("product 1 desc");
        product.setPrice(new BigDecimal(100));
        product.setSku("product 1 sku");
        product.setActive(true);
        product.setImageUrl("product1.png");
        return product;
    }

    protected Product getProduct2(){
        Product product2 = new Product();
        product2.setName("product 2");
        product2.setDescription("product 2 desc");
        product2.setPrice(new BigDecimal(200));
        product2.setSku("product 2 sku");
        product2.setActive(true);
        product2.setImageUrl("product2.png");
        return product2;
    }

    @Test
    void testCountMethod(){
        Product product = getProduct1();

        Product product2 = getProduct2();

        productRepository.saveAll(List.of(product, product2));

        long count = productRepository.count();
        System.out.println(count);
    }
We are using @DataJpaTest annotation to write a JUnit test ProductRepository count() method.

@AutoConfigureTestDatabase annotation is to disable embedded in-memory database support.

Output

Here is the output of the above JUnit test case we wrote for the testing count() method:

Hibernate: 
    insert 
    into
        products
        (active, date_created, description, image_url, last_updated, name, price, sku) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: 
    insert 
    into
        products
        (active, date_created, description, image_url, last_updated, name, price, sku) 
    values
        (?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: 
    select
        count(*) as col_0_0_ 
    from
        products product0_

Note that Spring Data JPA (Hibernate) produces the SQL query to count the number of records that exist in the database table. 

    select
        count(*) as col_0_0_ 
    from
        products product0_

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