事件监听器分发通知设计

public class EntryEvent
    implements CJWEvent
{
 
    public static final int ENTRY_ADDED = 100;
    public static final int ENTRY_DELETED = 101;
    public static final int ENTRY_MODIFIED = 102;
    public static final int ENTRY_MODERATION_MODIFIED = 103;
    public static final int ENTRY_RATED = 104;
    public static final int ENTRY_MOVED = 105;
    private int eventType;
    private Entry entry;
    private Date date;
    private Map params;
 
    public EntryEvent(int eventType, Entry entry, Map params)
    {
        this.eventType = eventType;
        this.entry = entry;
        this.params = params != null ? Collections.unmodifiableMap(params) : null;
        date = new Date();
    }
 
    public int getEventType()
    {
        return eventType;
    }
 
    public Entry getEntry()
    {
        return entry;
    }
 
    public Map getParams()
    {
        return params;
    }
 
    public Date getDate()
    {
        return date;
    }

public interface EntryListener
{
 
    public abstract void entryAdded(EntryEvent entryevent);
 
    public abstract void entryDeleted(EntryEvent entryevent);
 
    public abstract void entryMoved(EntryEvent entryevent);
 
    public abstract void entryModified(EntryEvent entryevent);
 
    public abstract void entryModerationModified(EntryEvent entryevent);
 
    public abstract void entryRated(EntryEvent entryevent);
}

public class EntryEventDispatcher
{
    static Logger logger = Logger.getLogger(EntryEventDispatcher.class.getName());
    private static EntryEventDispatcher instance = new EntryEventDispatcher();
    private ArrayList listeners;
 
    public static EntryEventDispatcher getInstance()
    {
        return instance;
    }
 
    private EntryEventDispatcher()
    {
        listeners = new ArrayList();
        List listenerList = CJWGlobals.getCJWProperties("eventListeners.MessageListener");
        for(int i = 0; i < listenerList.size(); i++)
        {
            String listenerStr = (String)listenerList.get(i);
            try
            {
                EntryListener listener = (EntryListener)ClassUtils.forName(listenerStr).newInstance();
                listeners.add(listener);
            }
            catch(Exception e)
            {
                logger.error("Error loading MessageListener", e);
            }
        }
 
    }
 
    public synchronized void addListener(EntryListener listener)
    {
        if(listener == null)
        {
            throw new NullPointerException();
        } else
        {
            listeners.add(listener);
            return;
        }
    }
 
    public synchronized void removeListener(EntryListener listener)
    {
        listeners.remove(listener);
    }
 
    public void dispatchEvent(EntryEvent event)
    {
        Profiler.begin("msgDispatchEvent");
        int eventType = event.getEventType();
        for(int i = 0; i < listeners.size(); i++)
            try
            {
                EntryListener listener = (EntryListener)listeners.get(i);
                String name = listener.getClass().getName();
                name = name.substring(name.lastIndexOf('.') + 1);
                Profiler.begin(name);
                switch(eventType)
                {
                case EntryEvent.ENTRY_ADDED: 
                    listener.entryAdded(event);
                    break;
 
                case EntryEvent.ENTRY_DELETED: 
                    listener.entryDeleted(event);
                    break;
 
                case EntryEvent.ENTRY_MODIFIED: 
                    listener.entryModified(event);
                    break;
 
                case EntryEvent.ENTRY_MODERATION_MODIFIED: 
                    listener.entryModerationModified(event);
                    break;
 
                case EntryEvent.ENTRY_RATED: 
                    listener.entryRated(event);
                    break;
 
                case EntryEvent.ENTRY_MOVED: 
                    listener.entryMoved(event);
                    break;
                }
                Profiler.end(name);
            }
            catch(Exception e)
            {
                logger.error(e);
            }
 
        Profiler.end("msgDispatchEvent");
    }

public class DbSearchManager
    implements SearchManager, CJWManager, EntryListener, TagListener{
...
    public void entryDeleted(EntryEvent event)
    {
        Entry message = event.getEntry();
        removeFromIndex(message);
    }
 
    public synchronized void initialize(){
...
        EntryEventDispatcher.getInstance().addListener(this);
...
}
...
 
}

...
public void deleteEntry(Entry entry){
...
        //事件分发,通知全文索引管理器进行删除
     EntryEvent event = new EntryEvent(EntryEvent.ENTRY_DELETED,entry,null);
       EntryEventDispatcher.getInstance().dispatchEvent(event);
...
}
...