Spring Data JPA Find Max Value

If you want to retrieve the maximum value of a specific column/field using Spring Data JPA, you can make use of the JPA's built-in max function. Let's see how to create a derived query method to find the maximum value.

Create JPA Entity

To demonstrate this example, assume we have the following entity Product with an attributes id, name, and price:

@Entity
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private Double price;

    // getters, setters, etc.
}

Create a Repository

To find the maximum price for all products, here is the custom query method:

public interface ProductRepository extends JpaRepository<Product, Long> {
    Optional<Product> findTopByOrderByPriceDesc();
}

Here:

findTopBy will limit the result to just one record.

OrderByPriceDesc will order the products by their price in descending order, so the first product will have the highest price.

Using the Repository in Service Class

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

    public Double getMaxProductPrice() {
        return productRepository.findTopByOrderByPriceDesc()
                .map(Product::getPrice) // Extract the price from the Product
                .orElse(null);
    }
}

Note that the method findTopByOrderByPriceDesc returns an Optional<Product> to handle the scenario when there are no products in the database. In such a case, the method would return an empty Optional, and the orElse(null) would convert it to a null value. Adjust as necessary based on your application's requirements.

Alternatively, if you're using a more complex query or have specific conditions, you can use the @Query annotation to define custom JPQL or native SQL queries within your repository.

For instance, here is a JPQL query to achieve the same result:

 @Query("SELECT p FROM Product p WHERE p.price = (SELECT MAX(p.price) FROM Product p)")
Optional<Product> findProductWithMaxPrice();