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Added event aggregator pattern.

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This commit is contained in:
Ilkka Seppala 2015-03-13 21:59:24 +02:00
parent c5a02266c8
commit ca59792916
15 changed files with 389 additions and 1 deletions
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event-aggregator/etc/classes.ucls Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
realizations="true" associations="true" dependencies="false" nesting-relationships="true">
<class id="1" language="java" name="com.iluwatar.KingsHand" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/KingsHand.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="805" y="431"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<interface id="2" language="java" name="com.iluwatar.EventObserver" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/EventObserver.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="784" y="586"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</interface>
<enumeration id="3" language="java" name="com.iluwatar.Weekday" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/Weekday.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="437" y="195"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</enumeration>
<class id="4" language="java" name="com.iluwatar.KingJoffrey" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/KingJoffrey.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="380" y="413"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="5" language="java" name="com.iluwatar.LordVarys" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/LordVarys.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="581" y="422"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="6" language="java" name="com.iluwatar.LordBaelish" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/LordBaelish.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="1050" y="422"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="7" language="java" name="com.iluwatar.EventEmitter" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/EventEmitter.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="1036" y="149"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="8" language="java" name="com.iluwatar.Scout" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/Scout.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="1275" y="422"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<enumeration id="9" language="java" name="com.iluwatar.Event" project="event-aggregator"
file="/event-aggregator/src/main/java/com/iluwatar/Event.java" binary="false" corner="BOTTOM_RIGHT">
<position height="-1" width="-1" x="721" y="159"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</enumeration>
<realization id="10">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="2"/>
</realization>
<association id="11">
<bendpoint x="927" y="360"/>
<end type="SOURCE" refId="7" navigable="false">
<attribute id="12" name="observers"/>
<multiplicity id="13" minimum="0" maximum="2147483647"/>
</end>
<end type="TARGET" refId="2" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<generalization id="14">
<end type="SOURCE" refId="1"/>
<end type="TARGET" refId="7"/>
</generalization>
<generalization id="15">
<end type="SOURCE" refId="6"/>
<end type="TARGET" refId="7"/>
</generalization>
<realization id="16">
<end type="SOURCE" refId="4"/>
<end type="TARGET" refId="2"/>
</realization>
<generalization id="17">
<end type="SOURCE" refId="8"/>
<end type="TARGET" refId="7"/>
</generalization>
<generalization id="18">
<end type="SOURCE" refId="5"/>
<end type="TARGET" refId="7"/>
</generalization>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>

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event-aggregator/pom.xml Normal file
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.iluwatar</groupId>
<artifactId>java-design-patterns</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>event-aggregator</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

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event-aggregator/src/main/java/com/iluwatar/App.java Normal file
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package com.iluwatar;
import java.util.ArrayList;
import java.util.List;
/**
*
* The Event Aggregator pattern channels events from multiple objects
* into a single object to simplify registration for clients.
*
* In the example LordBaelish, LordVarys and Scout deliver events to
* KingsHand. KingsHand, the event aggregator, then delivers the events
* to KingJoffrey.
*
*/
public class App {
public static void main(String[] args) {
KingJoffrey kingJoffrey = new KingJoffrey();
KingsHand kingsHand = new KingsHand(kingJoffrey);
List<EventEmitter> emitters = new ArrayList<>();
emitters.add(kingsHand);
emitters.add(new LordBaelish(kingsHand));
emitters.add(new LordVarys(kingsHand));
emitters.add(new Scout(kingsHand));
for (Weekday day: Weekday.values()) {
for (EventEmitter emitter: emitters) {
emitter.timePasses(day);
}
}
}
}

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event-aggregator/src/main/java/com/iluwatar/Event.java Normal file
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package com.iluwatar;
/**
*
* Event enumeration.
*
*/
public enum Event {
STARK_SIGHTED("Stark sighted"), WARSHIPS_APPROACHING("Warships approaching"), TRAITOR_DETECTED("Traitor detected");
private String description;
Event(String description) {
this.description = description;
}
public String toString() {
return description;
}
}

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event-aggregator/src/main/java/com/iluwatar/EventEmitter.java Normal file
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package com.iluwatar;
import java.util.LinkedList;
import java.util.List;
/**
*
* EventEmitter is the base class for event producers that can be observed.
*
*/
public abstract class EventEmitter {
private List<EventObserver> observers;
public EventEmitter() {
observers = new LinkedList<>();
}
public EventEmitter(EventObserver obs) {
this();
registerObserver(obs);
}
public void registerObserver(EventObserver obs) {
observers.add(obs);
}
protected void notifyObservers(Event e) {
for (EventObserver obs: observers) {
obs.onEvent(e);
}
}
public abstract void timePasses(Weekday day);
}

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event-aggregator/src/main/java/com/iluwatar/EventObserver.java Normal file
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package com.iluwatar;
/**
*
* Observers of events implement this interface.
*
*/
public interface EventObserver {
void onEvent(Event e);
}

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event-aggregator/src/main/java/com/iluwatar/KingJoffrey.java Normal file
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package com.iluwatar;
/**
*
* KingJoffrey observes events from KingsHand.
*
*/
public class KingJoffrey implements EventObserver {
@Override
public void onEvent(Event e) {
System.out.println("Received event from the King's Hand: " + e.toString());
}
}

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event-aggregator/src/main/java/com/iluwatar/KingsHand.java Normal file
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package com.iluwatar;
/**
*
* KingsHand observes events from multiple sources and delivers them
* to listeners.
*
*/
public class KingsHand extends EventEmitter implements EventObserver {
public KingsHand() {
super();
}
public KingsHand(EventObserver obs) {
super(obs);
}
@Override
public void onEvent(Event e) {
notifyObservers(e);
}
@Override
public void timePasses(Weekday day) {
// NOP
}
}

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event-aggregator/src/main/java/com/iluwatar/LordBaelish.java Normal file
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package com.iluwatar;
/**
*
* LordBaelish produces events.
*
*/
public class LordBaelish extends EventEmitter {
public LordBaelish() {
super();
}
public LordBaelish(EventObserver obs) {
super(obs);
}
@Override
public void timePasses(Weekday day) {
if (day.equals(Weekday.FRIDAY)) {
notifyObservers(Event.STARK_SIGHTED);
}
}
}

24
event-aggregator/src/main/java/com/iluwatar/LordVarys.java Normal file
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package com.iluwatar;
/**
*
* LordVarys produces events.
*
*/
public class LordVarys extends EventEmitter {
public LordVarys() {
super();
}
public LordVarys(EventObserver obs) {
super(obs);
}
@Override
public void timePasses(Weekday day) {
if (day.equals(Weekday.SATURDAY)) {
notifyObservers(Event.TRAITOR_DETECTED);
}
}
}

24
event-aggregator/src/main/java/com/iluwatar/Scout.java Normal file
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package com.iluwatar;
/**
*
* Scout produces events.
*
*/
public class Scout extends EventEmitter {
public Scout() {
super();
}
public Scout(EventObserver obs) {
super(obs);
}
@Override
public void timePasses(Weekday day) {
if (day.equals(Weekday.TUESDAY)) {
notifyObservers(Event.WARSHIPS_APPROACHING);
}
}
}

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event-aggregator/src/main/java/com/iluwatar/Weekday.java Normal file
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package com.iluwatar;
public enum Weekday {
MONDAY("Monday"), TUESDAY("Tuesday"), WEDNESDAY("Wednesday"), THURSDAY("Thursday"), FRIDAY("Friday"), SATURDAY("Saturday"), SUNDAY("Sunday");
private String description;
Weekday(String description) {
this.description = description;
}
public String toString() {
return description;
}
}

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event-aggregator/src/test/java/com/iluwatar/AppTest.java Normal file
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package com.iluwatar;
import org.junit.Test;
import com.iluwatar.App;
public class AppTest {
@Test
public void test() {
String[] args = {};
App.main(args);
}
}

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pom.xml
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@ -39,6 +39,7 @@
<module>servant</module>
<module>service-locator</module>
<module>null-object</module>
<module>event-aggregator</module>
</modules>
<dependencyManagement>