/* * Copyright (c) 2013 Mike Heath. All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ package cloudeventbus.client; /** * Holds the attributes associated with a subscription. Instances of this class are also {@link Iterable} so they can * be used in a {@code for} loop. * * <p>If the subscription has multiple {@link MessageHandler}s associated with it, each will be invoked when a message * is received. Additionally, each iterator created with this subscription will get each message received by this * subscription. If an iterator stops being used, its {@link MessageIterator#close()} method should be invoked to keep * messages from being queued unnecessarily and wasting memory. * * @see EventBus#subscribe(String, MessageHandler...) * @see EventBus#subscribe(String, Integer, MessageHandler...) * @author Mike Heath <elcapo@gmail.com> */ public interface Subscription extends Iterable<Message>, AutoCloseable { /** * Closes this subscription. Any {@link MessageHandler} objects associated with this request will no longer receive * messages for this subscription after this method is invoked. All {@link MessageIterator} objects created by * this subscription will also be closed. */ @Override void close(); /** * Returns the subscription's subject. * * @return the subscription's subject. */ String getSubject(); /** * Returns the number of messages this subscriptions has received. * * @return the number of messages this subscriptions has received. */ int getReceivedMessages(); /** * Returns the maximum number of messages this subscription will receive before being closed automatically. * * @return the maximum number of messages this subscription will receive or {@code null} if no maximum was specified. */ Integer getMaxMessages(); /** * Creates a {@link MessageIterator} to iterate over messages received on this subscription. Because * {@code Subscription} implements the {@link Iterable} interface, a subscription can be* used in a Java for loop. * For example: * <p/> * <pre> * for (Message message : nats.subscribe("foo.>") { * System.out.println(message); * } * </pre> * <p/> * The for loop may terminate with an exception when the subscription is closed. * * @return an iterator. */ @Override MessageIterator iterator(); /** * Registers a {@link MessageHandler} instance with this subscription that will be invoked every time the * subscription receives a message. * * @param messageHandler the message handler to be invoked * @return a {@code HandlerRegistration} for removing the {@code MessageHandler}. */ HandlerRegistration addMessageHandler(MessageHandler messageHandler); }