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npathainpathai
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Added another example of proxy pattern. Announcer from JMock demos by Nat Pryce.
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‎proxy/etc/proxy.png

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‎proxy/etc/proxy.ucls

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<?xml version="1.0" encoding="UTF-8"?>
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<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
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realizations="true" associations="true" dependencies="false" nesting-relationships="true">
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<class id="1" language="java" name="com.iluwatar.proxy.WizardTowerProxy" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/WizardTowerProxy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="142" width="214" x="260" y="438"/>
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<class-diagram version="1.1.10" icons="true" automaticImage="PNG" always-add-relationships="false"
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generalizations="true" realizations="true" associations="true" dependencies="false" nesting-relationships="true"
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router="FAN">
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<class id="1" language="java" name="com.iluwatar.proxy.example1.WizardTowerProxy" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/example1/WizardTowerProxy.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="407" y="454"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="2" language="java" name="com.iluwatar.proxy.Wizard" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/Wizard.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="124" width="117" x="187" y="274"/>
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<class id="2" language="java" name="com.iluwatar.proxy.example1.Wizard" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/example1/Wizard.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="684" y="455"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="3" language="java" name="com.iluwatar.proxy.WizardTower" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/WizardTower.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="106" width="130" x="344" y="274"/>
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<class id="3" language="java" name="com.iluwatar.proxy.example1.WizardTower" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/example1/WizardTower.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="408" y="217"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<generalization id="4">
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<class id="4" language="java" name="com.iluwatar.proxy.example1.App" project="proxy"
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file="/proxy/src/main/java/com/iluwatar/proxy/example1/App.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="141" y="455"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<dependency id="5">
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<end type="SOURCE" refId="4"/>
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<end type="TARGET" refId="1"/>
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</dependency>
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<dependency id="6">
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<end type="SOURCE" refId="3"/>
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<end type="TARGET" refId="2"/>
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</dependency>
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<generalization id="7">
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<end type="SOURCE" refId="1"/>
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<end type="TARGET" refId="3"/>
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</generalization>
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<dependency id="8">
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<end type="SOURCE" refId="1"/>
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<end type="TARGET" refId="2"/>
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</dependency>
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<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>

‎proxy/src/main/java/com/iluwatar/proxy/App.java renamed to ‎proxy/src/main/java/com/iluwatar/proxy/example1/App.java

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2020
* 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.proxy;
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package com.iluwatar.proxy.example1;
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/**
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*

‎proxy/src/main/java/com/iluwatar/proxy/Wizard.java renamed to ‎proxy/src/main/java/com/iluwatar/proxy/example1/Wizard.java

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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.proxy;
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package com.iluwatar.proxy.example1;
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/**
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*

‎proxy/src/main/java/com/iluwatar/proxy/WizardTower.java renamed to ‎proxy/src/main/java/com/iluwatar/proxy/example1/WizardTower.java

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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.proxy;
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package com.iluwatar.proxy.example1;
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/**
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*

‎proxy/src/main/java/com/iluwatar/proxy/WizardTowerProxy.java renamed to ‎proxy/src/main/java/com/iluwatar/proxy/example1/WizardTowerProxy.java

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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.proxy;
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package com.iluwatar.proxy.example1;
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/**
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*

‎proxy/src/main/java/com/iluwatar/proxy/example2/Announcer.java

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package com.iluwatar.proxy.example2;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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import java.lang.reflect.Proxy;
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import java.util.List;
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import java.util.concurrent.CopyOnWriteArrayList;
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public class Announcer {
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private HealthMonitor proxy;
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private List<HealthMonitor> listeners = new CopyOnWriteArrayList<>();
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public Announcer(Class<HealthMonitor> listenerType) {
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proxy = createProxy(listenerType);
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}
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private HealthMonitor createProxy(Class<HealthMonitor> listenerType) {
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return listenerType.cast(Proxy.newProxyInstance(listenerType.getClassLoader(),
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new Class<?>[] {listenerType}, (proxy, method, args) -> {
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invokeAll(method, args);
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return null;
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}));
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}
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private void invokeAll(Method method, Object[] args) {
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for (HealthMonitor listener : listeners) {
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try {
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method.invoke(listener, args);
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} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
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e.printStackTrace();
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}
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}
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}
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public void registerListener(HealthMonitor listener) {
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listeners.add(listener);
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}
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public HealthMonitor announce() {
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return proxy;
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}
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public void removeListener(HealthMonitor listener) {
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listeners.remove(listener);
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}
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}

‎proxy/src/main/java/com/iluwatar/proxy/example2/App.java

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package com.iluwatar.proxy.example2;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.Map.Entry;
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/**
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* An application representing a health monitoring system. Endpoints such as TCP connections, UDP
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* connections, DB connections keep fluctuating and may get disconnected. To monitor the health of
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* these endpoints user can attach health monitors to the endpoint and when the status of the
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* connectivity changes the health monitors are notified of the changes.
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*
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* The class that implements the Proxy pattern is {@link Announcer}.
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*
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* @see Announcer
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*
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* @author npathai
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*
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*/
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public class App {
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public static void main(String[] args) {
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EndPoint endPoint = new EndPoint("TCP Endpoint");
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ConsoleMonitor consoleMonitor = new ConsoleMonitor();
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HealthCounter counter = new HealthCounter();
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endPoint.addMonitor(consoleMonitor);
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endPoint.addMonitor(counter);
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endPoint.connected();
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endPoint.disconnect();
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endPoint.connected();
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endPoint.disconnect();
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endPoint.connected();
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counter.printCounters();
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}
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private static class ConsoleMonitor implements HealthMonitor {
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@Override
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public void disconnected(EndPoint endPoint) {
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System.out.println(endPoint + " is disconnected.");
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}
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@Override
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public void connected(EndPoint endPoint) {
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System.out.println(endPoint + " is connected");
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}
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}
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private static class HealthCounter implements HealthMonitor {
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private Map<String, Health> endPointNameToHealth = new HashMap<>();
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private class Health {
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private boolean connected;
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private int disconnectedCount = 0;
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private int connectedCount = 0;
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}
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@Override
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public void disconnected(EndPoint endPoint) {
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Health health = endPointNameToHealth.get(endPoint.getName());
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if (health == null) {
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health = new Health();
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endPointNameToHealth.put(endPoint.getName(), health);
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}
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health.connected = false;
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health.disconnectedCount++;
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}
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@Override
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public void connected(EndPoint endPoint) {
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Health health = endPointNameToHealth.get(endPoint.getName());
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if (health == null) {
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health = new Health();
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endPointNameToHealth.put(endPoint.getName(), health);
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}
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health.connected = true;
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health.connectedCount++;
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}
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public void printCounters() {
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for (Entry<String, Health> entry : endPointNameToHealth.entrySet()) {
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System.out.println(String.format("EndPoint: %s, Connected: %s, Connected Count: %d, Disconnected Count: %d",
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entry.getKey(), entry.getValue().connected, entry.getValue().connectedCount,
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entry.getValue().disconnectedCount));
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}
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}
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}
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}

‎proxy/src/main/java/com/iluwatar/proxy/example2/EndPoint.java

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package com.iluwatar.proxy.example2;
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public class EndPoint {
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private final String name;
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private final Announcer healthMonitors = new Announcer(HealthMonitor.class);
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public EndPoint(String name) {
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this.name = name;
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}
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public void addMonitor(HealthMonitor monitor) {
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healthMonitors.registerListener(monitor);
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}
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public void disconnect() {
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healthMonitors.announce().disconnected(this);
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}
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public void connected() {
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healthMonitors.announce().connected(this);
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}
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public String getName() {
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return name;
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}
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@Override
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public String toString() {
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return name;
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}
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}

‎proxy/src/main/java/com/iluwatar/proxy/example2/HealthMonitor.java

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package com.iluwatar.proxy.example2;
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public interface HealthMonitor {
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void disconnected(EndPoint endPoint);
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void connected(EndPoint endPoint);
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}

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