#467 data-bus: implement pattern

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

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

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+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 Paul Campbell
+
+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;
+
+/**
+ * .
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public class AbstractDataType implements DataType {
+
+  private DataBus dataBus;
+
+  @Override
+  public DataBus getDataBus() {
+    return dataBus;
+  }
+
+  @Override
+  public void setDataBus(DataBus dataBus) {
+    this.dataBus = dataBus;
+  }
+}

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

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+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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.StoppingData;
+import com.iluwatar.databus.data.StartingData;
+import com.iluwatar.databus.data.MessageData;
+import com.iluwatar.databus.members.CounterMember;
+import com.iluwatar.databus.members.StatusMember;
+import lombok.extern.slf4j.Slf4j;
+
+import java.time.LocalDateTime;
+
+/**
+ * The Data Bus pattern
+ * <p>
+ * <p>{@see http://wiki.c2.com/?DataBusPattern}</p>
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@Slf4j
+class App {
+
+  public static void main(String[] args) {
+    final DataBus bus = DataBus.getInstance();
+    bus.subscribe(new StatusMember(1));
+    bus.subscribe(new StatusMember(2));
+    final CounterMember foo = new CounterMember("Foo");
+    final CounterMember bar = new CounterMember("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()));
+  }
+}

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

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+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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 java.util.HashSet;
+import java.util.Set;
+
+/**
+ * The Data-Bus implementation.
+ *
+ * <p>This implementation uses a Singleton.</p>
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public class DataBus {
+
+  private static final DataBus INSTANCE = new DataBus();
+
+  private final Set<Member> listeners = new HashSet<>();
+
+  public static DataBus getInstance() {
+    return INSTANCE;
+  }
+
+  /**
+   * Register a member with the data-bus to start receiving events.
+   *
+   * @param member The member to register
+   */
+  public void subscribe(final Member member) {
+    this.listeners.add(member);
+  }
+
+  /**
+   * Deregister a member to stop receiving events.
+   *
+   * @param member The member to deregister
+   */
+  public void unsubscribe(final Member member) {
+    this.listeners.remove(member);
+  }
+
+  /**
+   * Publish and event to all members.
+   *
+   * @param event The event
+   */
+  public void publish(final DataType event) {
+    event.setDataBus(this);
+    listeners.forEach(listener -> listener.accept(event));
+  }
+}

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

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+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 Paul Campbell
+
+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;
+
+/**
+ * Events are sent via the Data-Bus.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+
+public interface DataType {
+
+  /**
+   * Returns the data-bus the event is being sent on.
+   *
+   * @return The data-bus
+   */
+  DataBus getDataBus();
+
+  /**
+   * Set the data-bus the event will be sent on.
+   *
+   * @param dataBus The data-bus
+   */
+  void setDataBus(DataBus dataBus);
+}

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

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+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 Paul Campbell
+
+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 java.util.function.Consumer;
+
+/**
+ * Members receive events from the Data-Bus.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public interface Member extends Consumer<DataType> {
+
+  void accept(DataType event);
+}

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

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+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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.data;
+
+import com.iluwatar.databus.AbstractDataType;
+import com.iluwatar.databus.DataType;
+import lombok.RequiredArgsConstructor;
+
+/**
+ * .
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@RequiredArgsConstructor
+public class MessageData extends AbstractDataType {
+
+  private final String message;
+
+  public String getMessage() {
+    return message;
+  }
+
+  public static DataType of(final String message) {
+    return new MessageData(message);
+  }
+}

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

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+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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.data;
+
+import com.iluwatar.databus.AbstractDataType;
+import com.iluwatar.databus.DataType;
+import lombok.RequiredArgsConstructor;
+
+import java.time.LocalDateTime;
+
+/**
+ * An event raised when applications starts, containing the start time of the application.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@RequiredArgsConstructor
+public class StartingData extends AbstractDataType {
+
+  private final LocalDateTime when;
+
+  public LocalDateTime getWhen() {
+    return when;
+  }
+
+  public static DataType of(final LocalDateTime when) {
+    return new StartingData(when);
+  }
+}

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

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+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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.data;
+
+import com.iluwatar.databus.AbstractDataType;
+import com.iluwatar.databus.DataType;
+import lombok.RequiredArgsConstructor;
+
+import java.time.LocalDateTime;
+
+/**
+ * .
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@RequiredArgsConstructor
+public class StoppingData extends AbstractDataType {
+
+  private final LocalDateTime when;
+
+  public LocalDateTime getWhen() {
+    return when;
+  }
+
+  public static DataType of(final LocalDateTime when) {
+    return new StoppingData(when);
+  }
+}

data-bus/src/main/java/com/iluwatar/databus/members/CounterMember.java

@@ -0,0 +1,53 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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.members;
+
+import com.iluwatar.databus.DataType;
+import com.iluwatar.databus.Member;
+import com.iluwatar.databus.data.MessageData;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * Receiver of Data-Bus events.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@Slf4j
+@RequiredArgsConstructor
+public class CounterMember implements Member {
+
+  private final String name;
+
+  @Override
+  public void accept(final DataType data) {
+    if (data instanceof MessageData) {
+      handleEvent((MessageData) data);
+    }
+  }
+
+  private void handleEvent(MessageData data) {
+    log.info("{} sees message {}", name, data.getMessage());
+  }
+}

data-bus/src/main/java/com/iluwatar/databus/members/StatusMember.java

@@ -0,0 +1,63 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * 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:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * 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.members;
+
+import com.iluwatar.databus.DataType;
+import com.iluwatar.databus.Member;
+import com.iluwatar.databus.data.MessageData;
+import com.iluwatar.databus.data.StartingData;
+import com.iluwatar.databus.data.StoppingData;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * Receiver of Data-Bus events.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@Slf4j
+@RequiredArgsConstructor
+public class StatusMember implements Member {
+
+  private final int id;
+
+  @Override
+  public void accept(final DataType data) {
+    if (data instanceof StartingData) {
+      handleEvent((StartingData) data);
+    } else if (data instanceof StoppingData) {
+      handleEvent((StoppingData) data);
+    }
+  }
+
+  private void handleEvent(StartingData data) {
+    log.info("Receiver #{} sees application started at {}", id, data.getWhen());
+  }
+
+  private void handleEvent(StoppingData data) {
+    log.info("Receiver #{} sees application stopping at {}", id, data.getWhen());
+    log.info("Receiver #{} sending goodbye message", id);
+    data.getDataBus().publish(MessageData.of(String.format("Goodbye cruel world from #%d!", id)));
+  }
+}

pom.xml

@@ -467,4 +467,4 @@
         </plugins>
     </reporting>
 
-</project>
+</project>