Vaporetto

Very lightweight proxy-based immutable value types for Java 8. (Compare phantom-pojos, an earlier iteration of the same idea).

Define types as follows:

public interface Address extends VType<Address> {
    Collection<String> addressLines();
    String postcode();
}

public interface Person extends VType<Person> {
    String name();
    int age();
    Address address();
}

Build values like this:

Person person = Vaporetto.build(Person.class, p -> p
    .with(Person::name, "Arthur Putey")
    .with(Person::age, 42)
    .with(Person::address, a -> a
        .with(Address::addressLines, "23 Acacia Avenue", "Sunderland")
        .with(Address::postcode, "VB6 5UX")));

Update values like this:

Person updated = person.update(p -> p
    .with(Person::age, 43));

Reify properties into lenses like this:

Property<Person, Address> address = Property.of(Person.class, Person::address);
Property<Address, String> postcode = Property.of(Address.class, Address::postcode);
Property<Person, String> addressPostcode = address.chain(postcode);

// OR
Property<Person, String> addressPostcode = Property.of(
    Property.of(Person.class, Person::Address),
    Address::postcode);

assertThat(addressPostcode.get(person), equalTo("VB6 5UX"));

Person updatedPerson = addressPostcode.update(person, "RA8 81T");
assertThat(updatedPerson.address().postcode(), equalTo("RA8 81T"));

poetix/vaporetto

Vaporetto