In this tutorial, we will learn how to write a LessThan query method or finder method using Spring Data JPA.

Spring Data JPA simplifies the process of constructing database queries by letting developers use method names to express their query requirements. One of these handy keywords is LessThan, which facilitates filtering results based on whether an entity field's value is less than a provided value.

Maven Dependencies

Create a Spring boot project and add the following maven dependencies to it:

                 <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>

		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>

Product Entity

Let's first create a Product entity class and add the following content to it:

package com.springdatajpa.springboot.entity;

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

import jakarta.persistence.*;
import java.math.BigDecimal;
import java.time.LocalDateTime;

@Entity
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
@Table(
        name = "products",
        schema = "ecommerce",
        uniqueConstraints = {
                @UniqueConstraint(
                        name = "sku_unique",
                        columnNames = "stock_keeping_unit"
                )
        }
)
public class Product {

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

    @Column(name = "stock_keeping_unit", nullable = false)
    private String sku;

    @Column(nullable = false)
    private String name;

    private String description;
    private BigDecimal price;
    private boolean active;
    private String imageUrl;

    @CreationTimestamp
    private LocalDateTime dateCreated;

    @UpdateTimestamp
    private LocalDateTime lastUpdated;
}

ProductRepository

Let's create ProductRepository which extends JpaRepository and add the following code to it:

package com.springdatajpa.springboot.repository;

import com.springdatajpa.springboot.entity.Product;
import org.springframework.data.jpa.repository.JpaRepository;
import java.math.BigDecimal;

public interface ProductRepository extends JpaRepository<Product, Long> {
    /**
     * Return the products whose price is less than given price as method parameter
     * @param price
     * @return
     */
    List<Product> findByPriceLessThan(BigDecimal price);
}

Spring Data JPA query method to find or retrieve products whose price is less than the given price as a method parameter:

    List<Product> findByPriceLessThan(BigDecimal price);

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.hibernate.ddl-auto = create-drop

spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

Make sure that you will create an ecommerce database before running the Spring boot application. Also, change the MySQL username and password as per your MySQL installation on your machine.

Testing Spring Data JPA - LessThan Query Method

Let's write the JUnit test to test Spring Data JPA - LessThan Query Method:

package com.springdatajpa.springboot.repository;

import com.springdatajpa.springboot.entity.Product;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.math.BigDecimal;

@SpringBootTest
public class QueryMethodsTest {

    @Autowired
    private ProductRepository productRepository;

    @Test
    void findByPriceLessThanMethod(){

        List<Product> products = productRepository.findByPriceLessThan(new BigDecimal(200));
        products.forEach((p) -> {
            System.out.println(p.getId());
            System.out.println(p.getName());
        });
    }
}

Here is the output of the above JUnit test: