Guava之EventBus使用總結

1.將EventBus封裝為單例模式使用

package priv.jack.demo.listener;

import java.util.Map;

import com.google.common.collect.Maps;
import com.google.common.eventbus.EventBus; 8 
/**
 * 事件總線工廠
 * 將EventBus封裝為單例模式使用
 * @author Jack
 *
 */
public class EventBusFactory {
    
    private volatile static EventBusFactory  INSTANCE ;
    
    /**
     * 保存已經注冊的監聽器，防止監聽器重復注冊
     */
    private Map<String, Class<? extends EventListener>> registerListenerContainers = Maps.newConcurrentMap() ;
    
    private EventBusFactory() {}
    
    public static EventBusFactory build() {
        if(INSTANCE == null) {
            synchronized (EventBusFactory.class) {
                if(INSTANCE == null) {
                    INSTANCE = new EventBusFactory() ;
                }
            }
        }
        return INSTANCE ;
    }
    
    private final EventBus EVENTBUS = new EventBus() ;
    
    /**
     * 事件轉發
     * @param event
     */
    public void postsEvent(SystemEvent event) {
        EVENTBUS.post(event) ;
    }
    
    /**
     * 監聽器注冊
     * @param clazz
     */
    public void register(Class<? extends EventListener> clazz)  {
        String clazzName = clazz.getSimpleName() ;
        if(registerListenerContainers.containsKey(clazzName)) {
            return ;
        }
        try {
            registerListenerContainers.put(clazzName, clazz) ;
            Object obj = registerListenerContainers.get(clazzName).newInstance();
            EVENTBUS.register(obj) ;
        } catch (Exception e) {
            e.printStackTrace();
        } 
    }
}

封裝之后，將EventBus的post和register也進行封裝

2.封裝SystemEvent作為事件的頂層父類，為了使EventBusFactory的postEvent更通用

package priv.jack.demo.listener.event;

/**
 * 系統事件父類
 * @author Jack
 *
 */
public class SystemEvent {
    
    public static final String MEMBER_DELETE_EVENT = "memberDelEvt" ;
    public static final String TEST_EVENT = "testEvt" ;

    private String eventName;
    
    public SystemEvent() {
        
    }
    
    public SystemEvent(String eventName) {
        this.eventName = eventName;
    }
    
    @Override
    public String toString() {
        return "SystemEvent [eventName=" + eventName + "]";
    }



    public String getEventName() {
        return eventName;
    }

    public void setEventName(String eventName) {
        this.eventName = eventName;
    }
}

3.編寫事件子類

package priv.jack.demo.listener.event;

public class TestEvent extends SystemEvent {

    private String testField;

    public String getTestField() {
        return testField;
    }

    public void setTestField(String testField) {
        this.testField = testField;
    }
    
    public TestEvent() {}
    
    public TestEvent(String eventName, String testField) {
        super(eventName) ;
        this.testField = testField ;
    }

}

package priv.jack.demo.listener.event;

import java.util.List;

/**
 * 成員刪除事件
 * 該事件觸發畫面合成修改操作
 * @author Jack
 *
 */
public class MemberDeletedEvent extends SystemEvent{

    private String confCreatorToken;

    private List<String> e164ListToOper ;

    private int cmd;
    
    public MemberDeletedEvent() {
    }
    
    public MemberDeletedEvent(String eventName) {
        super(eventName);
    }
    
    public MemberDeletedEvent(String eventName, String confCreatorToken, List<String> e164ListToOper, int cmd) {
        this(eventName) ;
        this.confCreatorToken = confCreatorToken ;
        this.e164ListToOper = e164ListToOper ;
        this.cmd = cmd ;
    }

    @Override
    public String toString() {
        return "MemberDeletedEvent [confCreatorToken=" + confCreatorToken + ", e164ListToOper=" + e164ListToOper + ", cmd=" + cmd + "]";
    }

    public String getConfCreatorToken() {
        return confCreatorToken;
    }

    public void setConfCreatorToken(String confCreatorToken) {
        this.confCreatorToken = confCreatorToken;
    }

    public List<String> getE164ListToOper() {
        return e164ListToOper;
    }

    public void setE164ListToOper(List<String> e164ListToOper) {
        this.e164ListToOper = e164ListToOper;
    }

    public int getCmd() {
        return cmd;
    }

    public void setCmd(int cmd) {
        this.cmd = cmd;
    }

}

4.編寫Listener接口類

public interface EventListener {

    public void action(SystemEvent event) ;
    
}

5.編寫Listener實現類

/**
 * 測試事件監聽類
 * @author Jack
 *
 */
public class TestEventListener implements EventListener{
    
    private Logger logger = LoggerFactory.getLogger("birdie") ;

    @Override
    @Subscribe
    @AllowConcurrentEvents
    public void action(SystemEvent event) {
        logger.info(String.format("[TestEventListener ] action, listener=%s event=%s", this.toString(), event.toString()));
        TestEvent subEvent = (TestEvent) event ;
        invoke(subEvent) ;
    }
    
    public void invoke(TestEvent testEvent) {
        logger.info(String.format("[TestEventListener ] action testEvent=%s", testEvent.toString()));
    }

}


/**
 * 成員刪除事件監聽器, 支持並發操作
 * @see MemberDeletedEvent
 * @see birdie-web下的EventBusTest
 * @author Jack
 *
 */
public class MemberDeletedEventListener implements EventListener{
    
    private Logger logger = LoggerFactory.getLogger("birdie") ;

    @Override
    @Subscribe
    @AllowConcurrentEvents
    public void action(SystemEvent event) {
        logger.info(String.format("[MemberDeletedEventListener ] action event=%s", event.toString()));
        MemberDeletedEvent subEvent = (MemberDeletedEvent) event ;
        invoke(subEvent) ;
    }
    
    public void invoke(MemberDeletedEvent memberDeletedEvent) {
        if(MtsOper.MT_DELETE.getOperCode() == memberDeletedEvent.getCmd()) {
            //...業務代碼
        }
    }

}

6.單元測試

public class EventBusTest {
    
    //測試重復注冊監聽器
    @Test
    public void testRepeatRegister() {
        final EventBus bus = new EventBus() ;
        bus.register(new TestEventListener());
        bus.register(new TestEventListener());
        
        TestEvent event = new TestEvent(SystemEvent.TEST_EVENT, "123") ;
        bus.post(event);
    }
    
    //測試並發操作
    //@Test
    public void testConcurrcy() {
        List<String> list = Lists.newArrayList("001#01") ;
        MemberDeletedEvent event = new MemberDeletedEvent(SystemEvent.MEMBER_DELETE_EVENT, "123", list , 1) ;
        for(int i=0 ; i < 100 ; i++) {
            final int cnt = i ;
            Thread t = new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } 
                    System.out.println("第"+ cnt+ "次");
                    EventBusFactory.build().register(MemberDeletedEventListener.class) ;
                }
            }) ;
            t.start(); 
        }
        try {
            Thread.sleep(6000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } 
        EventBusFactory.build().postsEvent(event);
    }

    //測試繼承結構下的事件分發
    @Test
    public void testInherit() {
        TestEvent event = new TestEvent(SystemEvent.TEST_EVENT, "123") ;
        EventBusFactory.build().register(TestEventListener.class) ;
        EventBusFactory.build().postsEvent(event);
    }
}

 

總結

1.支持類的繼承結構下的事件分發，但子類和父類都能收到事件。

2.@AllowConcurrentEvents 進行並發設置，經過簡單測試是OK的

相關問題

1.如何能夠很優雅的進行對監聽器進行集中且動態的注冊，讓其可擴展性更好

目前上面demo的代碼是在post之前進行register，並在register中進行重復注冊的屏蔽，如果新增監聽器的話需要修改代碼，可擴展性差

2.請大牛對代碼進行評價