I’ve been using Value objects a lot recently. Especially as I’ve been working with DDD. Lombok provides a convenient annotation to avoid writing lots of boilerplate code for Value object classes. The annotation will make the class final, add a constructor that takes all the arguments and make each field private and final.

Consider a model where we have two value objects, Animal and Human.

@Value
class Animal {
	Date birthday;
}

@Value
class Human extends Animal{
	String name;
}

If we use @Value on both classes, we’ll get a compilation error cannot extend final class.

Solution

@AllArgsConstructor
@Getter
class Animal {
	private final Date birthday;
}

@Value
@EqualsAndHashCode(callSuper = true)
class Human extends Animal{
	String name;

	public Human(Date birthday, String name) {
		super(birthday);
		this.name = name;
	}
}

Use @AllArgsConstructor and private final to mimic the behaviour of @Value. If you use Intellij, it will autocomplete the constructor for you so you don’t have to type it by hand. If you add/remove a field, just delete the constructor and generate it again.

Matt Reid

Lead Software Architect. Java and js enthusiast, badminton lover, foodie.

drei01 Matthew_Reid


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