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iluwatar#467 data-bus: implement pattern
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‎data-bus/README.md‎

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--- # this is so called 'Yaml Front Matter', read up on it here: http://jekyllrb.com/docs/frontmatter/
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layout: pattern # layout must allways be pattern
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title: Data Bus # the properly formatted title
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folder: data-bus # the folder name in which this pattern lies
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permalink: /patterns/data-bus/ # the permalink to the pattern, to keep this uniform please stick to /patterns/FOLDER/
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# both categories and tags are Yaml Lists
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# you can either just pick one or write a list with '-'s
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# usable categories and tags are listed here: https://github.com/iluwatar/java-design-patterns/blob/gh-pages/_config.yml
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categories: creational # categories of the pattern
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tags: # tags of the pattern
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- best
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- ever
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- awesome
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---
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## Intent
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Makes your code awesome
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![alt text](./etc/best_pattern.png "Best Pattern Ever")
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## Applicability
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Use the Best Pattern Ever pattern when
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* you want to be the best
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* you need to ...
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## Real world examples
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* [Nowhere](http://no.where.com)

‎data-bus/src/main/java/com/iluwatar/databus/AbstractDataType.java‎

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/*
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The MIT License (MIT)
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Copyright (c) 2016 Paul Campbell
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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package com.iluwatar.databus;
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/**
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* .
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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public class AbstractDataType implements DataType {
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private DataBus dataBus;
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@Override
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public DataBus getDataBus() {
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return dataBus;
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}
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@Override
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public void setDataBus(DataBus dataBus) {
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this.dataBus = dataBus;
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}
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}

‎data-bus/src/main/java/com/iluwatar/databus/App.java‎

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* <p>
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* <p>
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.databus;
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import com.iluwatar.databus.data.StoppingData;
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import com.iluwatar.databus.data.StartingData;
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import com.iluwatar.databus.data.MessageData;
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import com.iluwatar.databus.members.CounterMember;
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import com.iluwatar.databus.members.StatusMember;
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import lombok.extern.slf4j.Slf4j;
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import java.time.LocalDateTime;
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/**
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* The Data Bus pattern
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* <p>
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* <p>{@see http://wiki.c2.com/?DataBusPattern}</p>
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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@Slf4j
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class App {
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public static void main(String[] args) {
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final DataBus bus = DataBus.getInstance();
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bus.subscribe(new StatusMember(1));
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bus.subscribe(new StatusMember(2));
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final CounterMember foo = new CounterMember("Foo");
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final CounterMember bar = new CounterMember("Bar");
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bus.subscribe(foo);
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bus.publish(StartingData.of(LocalDateTime.now()));
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bus.publish(MessageData.of("Only Foo should see this"));
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bus.subscribe(bar);
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bus.publish(MessageData.of("Foo and Bar should see this"));
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bus.unsubscribe(foo);
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bus.publish(MessageData.of("Only Bar should see this"));
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bus.publish(StoppingData.of(LocalDateTime.now()));
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}
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}

‎data-bus/src/main/java/com/iluwatar/databus/DataBus.java‎

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* <p>
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* <p>
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.databus;
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import java.util.HashSet;
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import java.util.Set;
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/**
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* The Data-Bus implementation.
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*
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* <p>This implementation uses a Singleton.</p>
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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public class DataBus {
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private static final DataBus INSTANCE = new DataBus();
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private final Set<Member> listeners = new HashSet<>();
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public static DataBus getInstance() {
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return INSTANCE;
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}
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/**
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* Register a member with the data-bus to start receiving events.
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*
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* @param member The member to register
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*/
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public void subscribe(final Member member) {
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this.listeners.add(member);
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}
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/**
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* Deregister a member to stop receiving events.
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*
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* @param member The member to deregister
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*/
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public void unsubscribe(final Member member) {
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this.listeners.remove(member);
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}
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/**
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* Publish and event to all members.
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*
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* @param event The event
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*/
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public void publish(final DataType event) {
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event.setDataBus(this);
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listeners.forEach(listener -> listener.accept(event));
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}
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}

‎data-bus/src/main/java/com/iluwatar/databus/DataType.java‎

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/*
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The MIT License (MIT)
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Copyright (c) 2016 Paul Campbell
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19+
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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package com.iluwatar.databus;
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/**
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* Events are sent via the Data-Bus.
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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public interface DataType {
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/**
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* Returns the data-bus the event is being sent on.
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*
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* @return The data-bus
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*/
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DataBus getDataBus();
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/**
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* Set the data-bus the event will be sent on.
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*
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* @param dataBus The data-bus
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*/
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void setDataBus(DataBus dataBus);
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}

‎data-bus/src/main/java/com/iluwatar/databus/Member.java‎

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/*
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The MIT License (MIT)
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Copyright (c) 2016 Paul Campbell
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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package com.iluwatar.databus;
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import java.util.function.Consumer;
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/**
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* Members receive events from the Data-Bus.
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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public interface Member extends Consumer<DataType> {
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void accept(DataType event);
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}

‎data-bus/src/main/java/com/iluwatar/databus/data/MessageData.java‎

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
7+
* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9+
* copies of the Software, and to permit persons to whom the Software is
10+
* furnished to do so, subject to the following conditions:
11+
* <p>
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* The above copyright notice and this permission notice shall be included in
13+
* all copies or substantial portions of the Software.
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* <p>
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17+
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.databus.data;
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import com.iluwatar.databus.AbstractDataType;
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import com.iluwatar.databus.DataType;
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import lombok.RequiredArgsConstructor;
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/**
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* .
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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@RequiredArgsConstructor
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public class MessageData extends AbstractDataType {
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private final String message;
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public String getMessage() {
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return message;
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}
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public static DataType of(final String message) {
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return new MessageData(message);
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}
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}

‎data-bus/src/main/java/com/iluwatar/databus/data/StartingData.java‎

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
7+
* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9+
* copies of the Software, and to permit persons to whom the Software is
10+
* furnished to do so, subject to the following conditions:
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* <p>
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* <p>
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.databus.data;
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import com.iluwatar.databus.AbstractDataType;
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import com.iluwatar.databus.DataType;
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import lombok.RequiredArgsConstructor;
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import java.time.LocalDateTime;
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/**
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* An event raised when applications starts, containing the start time of the application.
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*
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* @author Paul Campbell (pcampbell@kemitix.net)
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*/
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@RequiredArgsConstructor
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public class StartingData extends AbstractDataType {
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private final LocalDateTime when;
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public LocalDateTime getWhen() {
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return when;
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}
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public static DataType of(final LocalDateTime when) {
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return new StartingData(when);
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}
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}

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