オシャレタプル for MessagePack-Java

Client.java

public class ClassifierClient {
	private static class TupleMessagePack extends MessagePack {
		protected TupleMessagePack(TemplateRegistry registry) {
			super(registry);
		}

		@SuppressWarnings({ "rawtypes", "unchecked" })
		public static MessagePack get() {
			TemplateRegistry reg = new TemplateRegistry(null);
			AnyTemplate any = new AnyTemplate(reg);
			reg.register(Tuple.class, new Tuple.TupleTemplate(any, any));
			reg.registerGeneric(Tuple.class, new GenericMapTemplate(reg,
					Tuple.TupleTemplate.class));
			return new TupleMessagePack(reg);
		}
	}

	public ClassifierClient(String host, int port, double timeout_sec)
			throws Exception {
		EventLoop loop = EventLoop.start(TupleMessagePack.get());
		c_ = new Client(host, port, loop);
		iface_ = c_.proxy(RPCInterface.class);
	}

	// ... snip ...
}

Tuple.java

import java.io.IOException;

import org.msgpack.MessageTypeException;
import org.msgpack.annotation.Message;
import org.msgpack.packer.Packer;
import org.msgpack.template.AbstractTemplate;
import org.msgpack.template.Template;
import org.msgpack.unpacker.Unpacker;

@Message
public class Tuple<E1, E2> {
	public E1 first;
	public E2 second;

	public Tuple() {
	}

	public Tuple(E1 first, E2 second) {
		this.first = first;
		this.second = second;
	}

	static class TupleTemplate<E1, E2> extends AbstractTemplate<Tuple<E1, E2>> {
		private Template<E1> e1Template;
		private Template<E2> e2Template;

		public TupleTemplate(Template<E1> e1Template, Template<E2> e2Template) {
			this.e1Template = e1Template;
			this.e2Template = e2Template;
		}

		public void write(Packer pk, Tuple<E1, E2> target, boolean required)
				throws IOException {
			if (target == null) {
				if (required) {
					throw new MessageTypeException("Attempted to write null");
				}
				pk.writeNil();
				return;
			}

			pk.writeArrayBegin(2);
			e1Template.write(pk, target.first);
			e2Template.write(pk, target.second);
			pk.writeArrayEnd();
		}

		public Tuple<E1, E2> read(Unpacker u, Tuple<E1, E2> to, boolean required)
				throws IOException {
			if (!required && u.trySkipNil()) {
				return null;
			}

			int n = u.readArrayBegin();
			if (n != 2) {
				throw new MessageTypeException(
						"Invalid number of elements: expected 2 but got " + n);
			}

			Tuple<E1, E2> tuple = to;
			if (tuple == null) {
				tuple = new Tuple<E1, E2>();
			}
			tuple.first = e1Template.read(u, null);
			tuple.second = e2Template.read(u, null);
			u.readArrayEnd();
			return tuple;
		}
	}
}

Usage.java

// Java 6
Tuple<String, Datum> train_datum = new Tuple<String, Datum>("japanese", datum);

// Java 7 だと、こう書ける!
Tuple<String, Datum> train_datum = new Tuple<>("japanese", datum);