Perfect Spring DTO (Normal)

Example.java

package com.scottlogic.springdto;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Positive;
import lombok.Value;

public class Example {
	@Value public static class CreateProductRequest{
		/**
		 * The product's name as should appear on the site.
		 * Any capitalisation here should be stored in the
		 * database but any filtering should be case-insensitive.
		 */
		@NotBlank
		String name;

		/**
		 * The amount that we sell a product for in GBP.
		 * This includes our margin but should not include
		 * any delivery fees or VAT.
		 */
		@Positive
		Double price;

		/**
		 * The amount that it costs us to purchase this product
		 * For the amount we sell a product for, see the Price.
		 * <b>This data is confidential</b>
		 */
		@Positive
		Double cost;
	}

	@Value public static class ProductResponse{
		/**
		 * The identifier for this product.
		 * IDs are unique amongst products but may be
		 * repeated across other entity types
		 */
		@Positive
		Long id;

		/**
		 * The product's name as should appear on the site.
		 * Any capitalisation here should be stored in the
		 * database but any filtering should be case-insensitive.
		 */
		@NotBlank	
		String name;

		/**
		 * The amount that we sell a product for in GBP.
		 * This includes our margin but should not include
		 * any delivery fees or VAT.
		 */
		@Positive
		Double price;
	}

	@Value public static class PrivateProductResponse{
		/**
		 * The product's name as should appear on the site.
		 * Any capitalisation here should be stored in the
		 * database but any filtering should be case-insensitive.
		 */
		@NotBlank
		Long id;

		/**
		 * The product's name as should appear on the site.
		 * Any capitalisation here should be stored in the
		 * database but any filtering should be case-insensitive.
		 */
		@NotBlank
		String name;

		/**
		 * The amount that we sell a product for in GBP.
		 * This includes our margin but should not include
		 * any delivery fees or VAT.
		 */
		@Positive
		Double price;

		/**
		 * The amount that it costs us to purchase this product
		 * For the amount we sell a product for, see the Price.
		 * <b>This data is confidential</b>
		 */
		@Positive
		Double cost;
	}

	private static Double getMarkup(Double price, Double cost){
		return (price - cost) / cost;
	}

	public static Double getMarkup(CreateProductRequest dto){
		return getMarkup(dto.getPrice(), dto.getCost());
	}

	public static Double getMarkup(PrivateProductResponse dto){
		return getMarkup(dto.getPrice(), dto.getCost());
	}
}

Why bother with validation annotations on the response objects? Nothing should be validating the response because you are creating it.