觀察者模式小 Demo
阿新 • • 發佈:2018-12-21
Demo
觀察者:
package com.example.observer; /** * 觀察者 * @author Dongguabai * @date 2018/12/16 14:21 */ public abstract class Observer { protected Subject subject; public Observer(Subject subject) { this.subject = subject; subject.addObserver(this); } protected abstract void notified(); }
package com.example.observer; /** * @author Dongguabai * @date 2018/12/16 14:38 */ public class Observer1 extends Observer{ public Observer1(Subject subject) { super(subject); } @Override protected void notified() { System.out.println("Observer1 ----"+subject.getState()); } }
package com.example.observer; /** * @author Dongguabai * @date 2018/12/16 14:38 */ public class Observer2 extends Observer{ public Observer2(Subject subject) { super(subject); } @Override protected void notified() { System.out.println("Observer ----"+subject.getState()); } }
目標物件:
package com.example.observer;
import java.util.ArrayList;
import java.util.List;
/**
* 目標物件
*
* @author Dongguabai
* @date 2018/12/16 14:21
*/
public class Subject {
private List<Observer> observers = new ArrayList<>(2);
//修改引數
private volatile int state;
public Subject() {
}
public void update(int state) {
if (state != this.state) {
this.state = state;
notifyAllObservers();
return;
}
System.out.println("No updates。。。。。。");
}
private void notifyAllObservers() {
observers.forEach(Observer::notified);
}
public void addObserver(Observer observer) {
this.observers.add(observer);
}
public int getState() {
return state;
}
}
Client :
package com.example.observer;
/**
* @author Dongguabai
* @date 2018/12/16 14:42
*/
public class Client {
public static void main(String[] args) {
Subject subject = new Subject();
new Observer1(subject);
new Observer2(subject);
System.out.println("-----test start------");
subject.update(1);
System.out.println("===================");
subject.update(1);
System.out.println("===================");
subject.update(2);
System.out.println("===================");
subject.update(3);
}
}
輸出結果:
-----test start------
Observer1 ----1
Observer2 ----1
===================
No updates。。。。。。
===================
Observer1 ----2
Observer2 ----2
===================
Observer1 ----3
Observer2 ----3
利用觀察者模式檢視執行緒的執行狀態
Observer:
package com.example.observer2;
/**
* Observer 介面
* @author Dongguabai
* @date 2018/12/17 9:39
*/
public interface LifeCycleListener {
void onEvent(ObservableRunnable.RunnableEvent event);
}
package com.example.observer2;
import java.util.List;
/**
* Observer
*
* @author Dongguabai
* @date 2018/12/17 9:39
*/
public class ThreadLifeCycleObserver implements LifeCycleListener {
private final Object LOCK = new Object();
public void concurrentQuery(List<String> ids) {
if (ids == null || ids.isEmpty()) {
return;
}
ids.forEach(id -> new Thread(new ObservableRunnable(this) {
@Override
public void run() {
try {
notifyChange(new RunnableEvent(RunnableState.RUNNING, Thread.currentThread(), null));
System.out.println("query for the id " + id);
//int i= 1/0;
Thread.sleep(1000L);
notifyChange(new RunnableEvent(RunnableState.DONE, Thread.currentThread(), null));
} catch (Exception e) {
notifyChange(new RunnableEvent(RunnableState.ERROR, Thread.currentThread(), e));
}
}
}, id).start());
}
@Override
public void onEvent(ObservableRunnable.RunnableEvent event) {
synchronized (LOCK) {
System.out.println("The runnable [" + event.getThread().getName() + "] data changed and state is [" + event.getState() + "]");
if (event.getCause() != null) {
System.out.println("The runnable [" + event.getThread().getName() + "] process failed.");
event.getCause().printStackTrace();
}
}
}
}
Subject:
package com.example.observer2;
/**
* Subject
* @author Dongguabai
* @date 2018/12/17 9:39
*/
public abstract class ObservableRunnable implements Runnable {
protected LifeCycleListener listener;
public ObservableRunnable(final LifeCycleListener listener) {
this.listener = listener;
}
protected void notifyChange(final RunnableEvent event) {
listener.onEvent(event);
}
public enum RunnableState {
RUNNING, ERROR, DONE
}
public static class RunnableEvent {
private final RunnableState state;
private final Thread thread;
private final Throwable cause;
public RunnableEvent(RunnableState state, Thread thread, Throwable cause) {
this.state = state;
this.thread = thread;
this.cause = cause;
}
public RunnableState getState() {
return state;
}
public Thread getThread() {
return thread;
}
public Throwable getCause() {
return cause;
}
}
}
Client:
package com.example.observer2;
import java.util.Arrays;
/**
* @author Dongguabai
* @date 2018/12/17 9:39
*/
public class ThreadLifeCycleClient {
public static void main(String[] args) {
new ThreadLifeCycleObserver().concurrentQuery(Arrays.asList("1", "2"));
}
}