data-bus/src/main/java/com/iluwatar/databus/App.java - master - githubmirror/java-design-patterns

data-bus/src/main/java/com/iluwatar/databus/App.java
75 строк4 KB
Ilkka Seppälä
deps: Refactor dependencies (#3224)
29 мар 2025, 20:34
29 мар 2025, 20:340ca162a
/*
 * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
 *
 * The MIT License
 * Copyright © 2014-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.iluwatar.databus;

import com.iluwatar.databus.data.MessageData;
import com.iluwatar.databus.data.StartingData;
import com.iluwatar.databus.data.StoppingData;
import com.iluwatar.databus.members.MessageCollectorMember;
import com.iluwatar.databus.members.StatusMember;
import java.time.LocalDateTime;

/**
 * The Data Bus pattern.
 *
 * @see <a href="http://wiki.c2.com/?DataBusPattern">http://wiki.c2.com/?DataBusPattern</a>
 *     <p>The Data-Bus pattern provides a method where different parts of an application may pass
 *     messages between each other without needing to be aware of the other's existence.
 *     <p>Similar to the {@code ObserverPattern}, members register themselves with the {@link
 *     DataBus} and may then receive each piece of data that is published to the Data-Bus. The
 *     member may react to any given message or not.
 *     <p>It allows for Many-to-Many distribution of data, as there may be any number of publishers
 *     to a Data-Bus, and any number of members receiving the data. All members will receive the
 *     same data, the order each receives a given piece of data, is an implementation detail.
 *     <p>Members may unsubscribe from the Data-Bus to stop receiving data.
 *     <p>This example of the pattern implements a Synchronous Data-Bus, meaning that when data is
 *     published to the Data-Bus, the publish method will not return until all members have received
 *     the data and returned.
 *     <p>The {@link DataBus} class is a Singleton.
 *     <p>Members of the Data-Bus must implement the {@link Member} interface.
 *     <p>Data to be published via the Data-Bus must implement the {@link DataType} interface.
 *     <p>The {@code data} package contains example {@link DataType} implementations.
 *     <p>The {@code members} package contains example {@link Member} implementations.
 *     <p>The {@link StatusMember} demonstrates using the DataBus to publish a message to the
 *     Data-Bus when it receives a message.
 */
class App {

  public static void main(String[] args) {
    final var bus = DataBus.getInstance();
    bus.subscribe(new StatusMember(1));
    bus.subscribe(new StatusMember(2));
    final var foo = new MessageCollectorMember("Foo");
    final var bar = new MessageCollectorMember("Bar");
    bus.subscribe(foo);
    bus.publish(StartingData.of(LocalDateTime.now()));
    bus.publish(MessageData.of("Only Foo should see this"));
    bus.subscribe(bar);
    bus.publish(MessageData.of("Foo and Bar should see this"));
    bus.unsubscribe(foo);
    bus.publish(MessageData.of("Only Bar should see this"));
    bus.publish(StoppingData.of(LocalDateTime.now()));
  }
}