Sum in Custom Query in Spring Data JPA

package com.demo.repositories;

import java.math.BigDecimal;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import com.demo.entities.Product;

@Repository("productRepository")
public interface ProductRepository extends CrudRepository<Product, Integer> {

    @Query(value = "SELECT sum(quantity) FROM Product")
    public Long sumQuantities();

    @Query(value = "SELECT sum(quantity * price) FROM Product")
    public BigDecimal total();

}

package com.demo.services;

import java.math.BigDecimal;

public interface ProductService {

    public Long sumQuantities();

    public BigDecimal total();

}

package com.demo.services;

import java.math.BigDecimal;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.demo.repositories.ProductRepository;

@Transactional
@Service("productService")
public class ProductServiceImpl implements ProductService {

    @Autowired
    private ProductRepository productRepository;

    @Override
    public Long sumQuantities() {
        return productRepository.sumQuantities();
    }

    @Override
    public BigDecimal total() {
        return productRepository.total();
    }

}

package com.demo.main;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;

import com.demo.JPAConfiguration;
import com.demo.services.ProductService;

public class Demo {

    public static void main(String[] args) {
        try {
            AbstractApplicationContext context = new AnnotationConfigApplicationContext(JPAConfiguration.class);
            ProductService productService = context.getBean(ProductService.class);
            System.out.println("Sum Quantities: " + productService.sumQuantities());
            System.out.println("Total: " + productService.total());
            context.close();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }

}

package com.demo.entities;

import java.io.Serializable;

import java.math.BigDecimal;

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

@Entity
@Table(name = "product")
public class Product implements Serializable {
    private static final long serialVersionUID = 1L;

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

    private String name;

    private BigDecimal price;

    private int quantity;

    private String description;

    private String photo;

    private boolean featured;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public BigDecimal getPrice() {
        return price;
    }

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

    public int getQuantity() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }

    public String getDescription() {
        return description;
    }

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

    public String getPhoto() {
        return photo;
    }

    public void setPhoto(String photo) {
        this.photo = photo;
    }

    public boolean isFeatured() {
        return featured;
    }

    public void setFeatured(boolean featured) {
        this.featured = featured;
    }

}

package com.demo;
    
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class LearnSpringDataJPA {

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

package com.demo;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import com.demo.services.ProductService;
import com.demo.services.ProductServiceImpl;

@Configuration
@EnableAutoConfiguration
@EnableTransactionManagement
@EnableJpaRepositories(basePackages = { "com.demo.repositories" })
@ComponentScan("com.demo")
@PropertySource("classpath:application.properties")
public class JPAConfiguration {

    @Bean
    public ProductService productService() {
        return new ProductServiceImpl();
    }

}

spring.datasource.url= jdbc:mysql://localhost:3306/springbootdatajpa
spring.datasource.username=root
spring.datasource.password=123456

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.0.M1</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.demo</groupId>
    <artifactId>SpringBootDataJPA</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>SpringBootDataJPA</name>
    <description>Spring Boot Data JPA</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <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>

        <dependency>
            <groupId>net.bytebuddy</groupId>
            <artifactId>byte-buddy</artifactId>
            <version>1.9.12</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </pluginRepository>
    </pluginRepositories>

</project>