业务事件模型的实现

　　在实际业务开发过程中，很经常应用到观察者模式。大致的处理流程是说在模块初始化的时候，注册若干观察者，然后它们处理自己感兴趣的内容。当某一个具体的事件发生的时候，遍历观察者队列，然后”观察者“们就根据之前约定的具体情况，处理自己关注的事件。其实观察者模式本人认为更确切的说法应该是：事件通知模型。那么现在，我们就用传统的Java语言来实现一下（具体可以查看代码的注释，写的挺详细了）。

　　业务事件定义如下：

/**
 * @filename:BusinessEvent.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:业务事件定义
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

public class BusinessEvent {

    // 某种具体的业务事件的数据内容
    private Object businessData;

    // 某种具体的业务事件的事件类型
    private String businessEventType;

    public BusinessEvent(String businessEventType, Object businessData) {
        this.businessEventType = businessEventType;
        this.businessData = businessData;
    }

    public Object getBusinessData() {
        return this.businessData;
    }

    public String getBusinessEventType() {
        return this.businessEventType;
    }

}

　　接着就是业务事件监听器的定义了

/**
 * @filename:BusinessEventListener.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:业务事件监听器定义
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

public interface BusinessEventListener {
    
    //事件接口定义
    public void execute(BusinessEvent event);

}

　　业务事件，总要有个管理者吧，那现在就实现一个

/**
 * @filename:BusinessEventManagement.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:业务事件管理器定义
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

//业务事件管理器
public class BusinessEventManagement {

    private Map<String, List<BusinessEventListener>> map = new HashMap<String, List<BusinessEventListener>>();

    public BusinessEventManagement() {

    }

    // 注册业务事件监听器
    public boolean addBusinessEventListener(String BusinessEventType,BusinessEventListener listener) {
        List<BusinessEventListener> listeners = map.get(BusinessEventType);
        
        if (null == listeners) {
            listeners = new ArrayList<BusinessEventListener>();
        }
        
        boolean result = listeners.add(listener);
        
        map.put(BusinessEventType, listeners);
        
        return result;
    }

    // 移除业务事件监听器
    public boolean removeBusinessEventListener(String BusinessEventType,BusinessEventListener listener) {
        List<BusinessEventListener> listeners = map.get(BusinessEventType);

        if (null != listeners) {
            return listeners.remove(listener);
        }

        return false;
    }

    // 获取业务事件监听器队列
    public List<BusinessEventListener> getBusinessEventListeners(String BusinessEventType) {
        return map.get(BusinessEventType);
    }

}

　　再来一个事件的发送者，来负责事件的派发

/**
 * @filename:BusinessEventNotify.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:业务事件发送者
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

import java.util.List;

public class BusinessEventNotify {

    private BusinessEventManagement businessEventManagement;;

    public BusinessEventNotify(BusinessEventManagement businessEventManagement) {
        this.businessEventManagement = businessEventManagement;
    }

    // 事件派发
    public void notify(BusinessEvent BusinessEvent) {
        if (null == BusinessEvent) {
            return;
        }

        List<BusinessEventListener> listeners = businessEventManagement.getBusinessEventListeners(BusinessEvent.getBusinessEventType());

        if (null == listeners) {
            return;
        }

        for (BusinessEventListener listener : listeners) {
            listener.execute(BusinessEvent);
        }
    }
}

　　关键的来了，下面可以根据自己的业务规定，注册若干个事件的监听器。下面我们就先注册两个监听器，分别是短信监听器、彩铃监听器，然后执行自己对“感兴趣”事件进行的操作。

/**
 * @filename:SendSmsListener.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:短信消息监听器
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

public class SendSmsListener implements BusinessEventListener {

    @Override
    public void execute(BusinessEvent event) {
        System.out.println("监听器:" + this + "接收到业务事件，业务事件类型是["
                + event.getBusinessEventType() + "] ## 业务事件附带的数据["
                + event.getBusinessData() + "]");
    }

}

/**
 * @filename:ColorRingListener.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:彩铃消息监听器
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

public class ColorRingListener implements BusinessEventListener {

    @Override
    public void execute(BusinessEvent event) {
        System.out.println("监听器:" + this + "接收到业务事件，业务事件类型是["
                + event.getBusinessEventType() + "] ## 业务事件附带的数据["
                + event.getBusinessData() + "]");
    }

}

　　好了，全部的框架都完成了，那现在我们把上述模块完整的调用起来。

/**
 * @filename:Main.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:主函数
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.businessevent;

public class Main {

    /**
     * @param args
     */
    public static void main(String[] args) {
        
        // 注册监听器
        BusinessEventManagement businessEventManagement = new BusinessEventManagement();
        
        businessEventManagement.addBusinessEventListener("彩铃监听器",new ColorRingListener());
        businessEventManagement.addBusinessEventListener("短信监听器",new SendSmsListener());

        // 业务事件触发
        BusinessEventNotify sender = new BusinessEventNotify(businessEventManagement);
        
        sender.notify(new BusinessEvent("彩铃监听器", "ReadBusinessEvent"));
        sender.notify(new BusinessEvent("短信监听器", "WriteBusinessEvent"));
    }

}

　　彩铃监听器感兴趣的事件是读事件（ReadBusinessEvent），短信监听器感兴趣的事件是写事件（WriteBusinessEvent）。运行起来之后，发现果然组织的很好。当然有人会说，上面的情况JDK里面已经有现成的类（java.util.EventObject、java.util.EventListener）支持了。那下面我们就根据上面的例子，利用Spring框架来模拟一下事件模型是如何更优雅的应用的。

　　在Spring里面，所有事件的基类是ApplicationEvent，那我们从这个类派生一下，重新定义一下我们的业务事件。代码如下

/**
 * @filename:BusinessEvent.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:业务事件定义
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.spring;

import org.springframework.context.ApplicationEvent;

public class BusinessEvent extends ApplicationEvent {
    
    // 某种具体的业务事件的数据内容
    private Object businessData;

    // 某种具体的业务事件的事件类型
    private String businessEventType;

    public BusinessEvent(String businessEventType, Object businessData) {
        super(businessEventType);

        this.businessEventType = businessEventType;
        this.businessData = businessData;
    }

    public Object getBusinessData() {
        return this.businessData;
    }

    public String getBusinessEventType() {
        return this.businessEventType;
    }
}

　　同样的，事件的发送者也要进行一下调整，代码如下

/**
 * @filename:BusinessEventNotify.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:业务事件发送者
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.spring;

import java.util.List;

import newlandframework.spring.BusinessEvent;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class BusinessEventNotify implements ApplicationContextAware {

    private List<String> businessListenerList;
    
    private ApplicationContext ctx;

    public void setBusinessListenerList(List<String> businessListenerList) {
        this.businessListenerList = businessListenerList;
    }

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

    public void notify(BusinessEvent businessEvent) {
        if (businessListenerList.contains(businessEvent.getBusinessEventType())) {
            BusinessEvent event = new BusinessEvent(
                    businessEvent.getBusinessEventType(),
                    businessEvent.getBusinessData());
            ctx.publishEvent(event);

            return;
        }
    }
}

　　下面我们就来注册一下Spring方式的短信、彩铃监听器：

/**
 * @filename:SendSmsListener.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:短信消息监听器
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.spring;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;

public class SendSmsListener implements ApplicationListener {
    
    final String strKey = "SMS";

    public void onApplicationEvent(ApplicationEvent event) {
        // 这里你可以截取感兴趣的实际类型
        if (event instanceof BusinessEvent) {
            BusinessEvent businessEvent = (BusinessEvent) event;

            if (businessEvent.getBusinessEventType().toUpperCase().contains(strKey)) {
                System.out.println("监听器:" + this + "接收到业务事件，业务事件类型是["
                        + businessEvent.getBusinessEventType()
                        + "] ## 业务事件附带的数据[" + businessEvent.getBusinessData()
                        + "]");
            }
        }
    }
}

/**
 * @filename:ColorRingListener.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:彩铃消息监听器
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.spring;

import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;

public class ColorRingListener implements ApplicationListener {

    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof BusinessEvent) {
            BusinessEvent businessEvent = (BusinessEvent) event;
            System.out.println("监听器:" + this + "接收到业务事件，业务事件类型是["
                    + businessEvent.getBusinessEventType() + "] ## 业务事件附带的数据["
                    + businessEvent.getBusinessData() + "]");
        }
    }
}

　　最后我们编写一下Spring的依赖注入的配置文件spring-event.xml，当然事件的监听器也是在这里面依赖注入实现自动装配的。

<?xml version="1.0" encoding="GBK"?>
<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-2.5.xsd"
    default-autowire="byName">
    <bean id="smsListener" class="newlandframework.spring.SendSmsListener" />
    <bean id="ringListener" class="newlandframework.spring.ColorRingListener" />
    <bean id="event" class="newlandframework.spring.BusinessEventNotify">
        <property name="businessListenerList">
            <list>
                <value>DealColorRing</value>
                <value>DealSms</value>
            </list>
        </property>
    </bean>
</beans>

　　一切准备就绪，现在我们把上面Spring方式实现的事件模型，完整的串起来，代码如下：

/**
 * @filename:Main.java
 *
 * Newland Co. Ltd. All rights reserved.
 * 
 * @Description:主函数
 * @author tangjie
 * @version 1.0
 * 
 */

package newlandframework.spring;

import newlandframework.spring.BusinessEvent;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("newlandframework/spring/spring-event.xml");

        BusinessEventNotify sender = (BusinessEventNotify) ctx.getBean("event");

        sender.notify(new BusinessEvent("DealColorRing", "ReadBusinessEvent"));

        sender.notify(new BusinessEvent("DealSms", "ReadBusinessEvent"));
    }
}

　　运行的结果如下，非常完美，不是么？