spring-boot-2.0.3不一样系列之番外篇 - springb…

package com.lee.myobserver;


/**
 * 抽象主题
 * 提供具体主题需要实现的接口
 */
public interface Subject {

    /**
     * 注册观察者
     * @param observer
     */
    void attach(Observer observer);

    /**
     *  移除观察者
     *  @param observer
     */
    void detach(Observer observer);

    /**
     * 通知所有注册的观察者
     */
    void notifyObservers();
}

package com.lee.myobserver;

/**
 * 抽象观察者
 * 提供具体观察者需要实现的接口
 */
public interface Observer {

    /**
     *
     */
    void update(String state);
}

package com.lee.myobserver.impl;

import com.lee.myobserver.Observer;
import com.lee.myobserver.Subject;

import java.util.ArrayList;
import java.util.List;

/**
 * 具体主题
 */
public class ConcreteSubject implements Subject {

    private List<Observer> observerList = new ArrayList<>();
    private String state;

    @Override
    public void attach(Observer observer) {
        this.observerList.add(observer);
        System.out.println("向ConcreteSubject注册了一个观察者");
    }

    @Override
    public void detach(Observer observer) {
        this.observerList.remove(observer);
        System.out.println("从ConcreteSubject移除了一个观察者");
    }

    @Override
    public void notifyObservers() {
        this.observerList.forEach(observer -> observer.update(this.state));
    }

    public void changeState(String state) {
        this.state = state;
        this.notifyObservers();
    }
}

package com.lee.myobserver.impl;

import com.lee.myobserver.Observer;

/**
 * 具体观察者
 */
public class ConcreteObserver implements Observer {

    @Override
    public void update(String state) {
        System.out.println("我被通知了，我要改变状态为：" + state);
    }
}

package com.lee.test;

import com.lee.myobserver.Observer;
import com.lee.myobserver.impl.ConcreteObserver;
import com.lee.myobserver.impl.ConcreteSubject;

public class MyObserverTest {

    public static void main(String[] args) {
        ConcreteSubject subject = new ConcreteSubject();
        Observer observer = new ConcreteObserver();
        subject.attach(observer);
        subject.changeState("new state");
    }
}

package java.util;

/**
 * 抽象主题，用普通类实现
 */
public class Observable {
    private boolean changed = false;
    private Vector<Observer> obs;

    
    /**
     * 构建一个含有0个观察者的主题
     */
    public Observable() {
        obs = new Vector<>();
    }

    /**
     * 注册某个观察者到obs中
     */
    public synchronized void addObserver(Observer o) {
        if (o == null)
            throw new NullPointerException();
        if (!obs.contains(o)) {
            obs.addElement(o);
        }
    }

    /**
     * 从obs中移除某个观察者
     */
    public synchronized void deleteObserver(Observer o) {
        obs.removeElement(o);
    }

    /**
     * 相当于notifyObservers(null)，具体看下面那个
     */
    public void notifyObservers() {
        notifyObservers(null);
    }

    /**
     * 如果本对象有变化，则通知所有注册了的观察者，调用他们的update方法
     */
    public void notifyObservers(Object arg) {
        /*
         * a temporary array buffer, used as a snapshot of the state of
         * current Observers.
         */
        Object[] arrLocal;

        synchronized (this) {
            if (!changed)
                return;
            arrLocal = obs.toArray();
            clearChanged();
        }

        for (int i = arrLocal.length-1; i>=0; i--)
            ((Observer)arrLocal[i]).update(this, arg);
    }

    /**
     * 清空obs
     */
    public synchronized void deleteObservers() {
        obs.removeAllElements();
    }

    /**
     * 将changed设置成true，标明本对象发生了变化
     */
    protected synchronized void setChanged() {
        changed = true;
    }

    /**
     * 将changed重置成false
     */
    protected synchronized void clearChanged() {
        changed = false;
    }

    /**
     * 检测本对象是否发生了变化
     */
    public synchronized boolean hasChanged() {
        return changed;
    }

    /**
     * 返回注册的观察者数量
     */
    public synchronized int countObservers() {
        return obs.size();
    }
}

package java.util;

/**
 * 抽象观察者，接口实现
 */
public interface Observer {
    /**
     * 当被观察者对象发生改变时，此方法被调用
     */
    void update(Observable o, Object arg);
}

package com.lee.jdkobserver;

import java.util.Observable;

/**
 * 具体主题
 */
public class Watched extends Observable {
    private String data = "";

    public void changeData(String data) {
        if (this.data.equals(data)) {
            return;
        }
        this.data = data;
        setChanged();
        notifyObservers(this.data);
    }
}

package com.lee.jdkobserver;

import java.util.Observable;
import java.util.Observer;

/**
 * 具体观察者，实现jdk中的Observer
 */
public class Watcher implements Observer {

    @Override
    public void update(Observable o, Object arg) {
        System.out.println("数据改变成了：" + arg);
    }
}

package com.lee.test;

import com.lee.jdkobserver.Watched;
import com.lee.jdkobserver.Watcher;

import java.util.Observer;

public class JdkObserverTest {

    public static void main(String[] args) {
        Watched watched = new Watched();
        Observer observer = new Watcher();
        watched.addObserver(observer);
        watched.changeData("first");
        watched.changeData("second");
        watched.changeData("third");
        watched.changeData("fourth");
    }
}

/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context;

import java.util.EventObject;

/**
 * Class to be extended by all application events. Abstract as it
 * doesn't make sense for generic events to be published directly.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 */
public abstract class ApplicationEvent extends EventObject {

    /** use serialVersionUID from Spring 1.2 for interoperability */
    private static final long serialVersionUID = 7099057708183571937L;

    /** System time when the event happened */
    private final long timestamp;


    /**
     * Create a new ApplicationEvent.
     * @param source the object on which the event initially occurred (never {@code null})
     */
    public ApplicationEvent(Object source) {
        super(source);
        this.timestamp = System.currentTimeMillis();
    }


    /**
     * Return the system time in milliseconds when the event happened.
     */
    public final long getTimestamp() {
        return this.timestamp;
    }

}

/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context;

import java.util.EventListener;

/**
 * Interface to be implemented by application event listeners.
 * Based on the standard {@code java.util.EventListener} interface
 * for the Observer design pattern.
 *
 * <p>As of Spring 3.0, an ApplicationListener can generically declare the event type
 * that it is interested in. When registered with a Spring ApplicationContext, events
 * will be filtered accordingly, with the listener getting invoked for matching event
 * objects only.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @param <E> the specific ApplicationEvent subclass to listen to
 * @see org.springframework.context.event.ApplicationEventMulticaster
 */
@FunctionalInterface
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {

    /**
     * Handle an application event.
     * @param event the event to respond to
     */
    void onApplicationEvent(E event);

}

package com.lee.springevent.event;

import org.springframework.context.ApplicationEvent;

/**
 * 短信事件，事件信息的载体
 * 可以从中获取事件源信息，本例中source不代表事件源
 */
public class MessageEvent extends ApplicationEvent {

    public MessageEvent(Object source) {
        super(source);
    }
}

package com.lee.springevent.listener;

import com.lee.springevent.event.MessageEvent;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;

public class MessageListener implements ApplicationListener{

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if(event instanceof MessageEvent) {
            String phoneNumber = (String)event.getSource();
            System.out.println("我已收到通知：即将向"+phoneNumber+"发短信了...");
        }
    }
}

package com.lee.springevent.service;

import com.lee.springevent.event.MessageEvent;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

/**
 * ApplicationContextAware，能够获取spring的上下文环境
 *
 * MessageService相当于之前说的事件环境
 */
public class MessageService implements ApplicationContextAware {

    private ApplicationContext ctx;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.ctx = applicationContext;
    }

    public void sendMessage(String phoneNumber)
    {
        MessageEvent evt = new MessageEvent(phoneNumber);

        // 发布事件
        ctx.publishEvent(evt);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="messageService" class="com.lee.springevent.service.MessageService" />
    <bean id="messageListener" class="com.lee.springevent.listener.MessageServiceListener" />

</beans>

package com.lee.test;

import com.lee.springevent.service.MessageService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringEventTest {

    public static void main(String[] args) {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-event.xml");
        MessageService messageService = (MessageService) applicationContext.getBean("messageService");
        messageService.sendMessage("1574480311");
    }
}