利用Java的观察者模式编写一个简单的Java事件监听案例

图不重要，看代码。

下面直接编写代码

package cn.majingjing.tzx.event;
public interface EntryListener {
    public abstract void entryAdded(EntryEvent entryevent);
    public abstract void entryDeleted(EntryEvent entryevent);
    public abstract void entryModified(EntryEvent entryevent);
}

package cn.majingjing.tzx.event;
public class Entry {
    private long id;
    private String name;
    ...省略get，set方法
}

package cn.majingjing.tzx.event;
import java.util.Collections;
import java.util.Date;
import java.util.Map;
public class EntryEvent {
    public static final int ENTRY_ADDED = 100;
    public static final int ENTRY_DELETED = 101;
    public static final int ENTRY_MODIFIED = 102;
    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;
    }
}

package cn.majingjing.tzx.event;
import java.util.ArrayList;
public class EntryEventDispatcher {
    private static EntryEventDispatcher instance = new EntryEventDispatcher();
    private ArrayList<EntryListener> listeners = new ArrayList<EntryListener>();
    public static EntryEventDispatcher getInstance() {
        return instance;
    }
    private EntryEventDispatcher() {
        String[] observers = PropertyMgr.getProperty("observers").split(",");
        for (String s : observers) {
            System.out.println(s);
            try {
                this.addListener((EntryListener) (Class.forName(s).newInstance()));
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
    }
    public synchronized void addListener(EntryListener listener) {
        System.out.println(":" + listener);
        if (listener == null) {
            System.out.println(":" + listener);
            throw new NullPointerException();
        } else {
            listeners.add(listener);
            return;
        }
    }
    public synchronized void removeListener(EntryListener listener) {
        listeners.remove(listener);
    }
    public void dispatchEvent(EntryEvent event) {
        // System.out.println("msgDispatchEvent");
        int eventType = event.getEventType();
        long t1 = System.currentTimeMillis();
        System.out.println("kaishi=" + t1);
        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);
                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;
                }
            } catch (Exception e) {
                // logger.error(e);
            }
        }
        System.out.println("cost time=" + (System.currentTimeMillis() - t1));
        // Profiler.end("msgDispatchEvent");
    }
}

package cn.majingjing.tzx.event.manager;
import cn.majingjing.tzx.event.EntryEvent;
import cn.majingjing.tzx.event.EntryListener;
public class IndexManager implements EntryListener {
    @Override
    public void entryAdded(EntryEvent entryevent) {
        System.out.println("IndexManager add");
    }
    @Override
    public void entryDeleted(EntryEvent entryevent) {
        System.out.println("IndexManager del");
    }
    @Override
    public void entryModified(EntryEvent entryevent) {
        System.out.println("IndexManager modify");
    }
}

package cn.majingjing.tzx.event.manager;
import cn.majingjing.tzx.event.EntryEvent;
import cn.majingjing.tzx.event.EntryListener;
public class EmailManager implements EntryListener {
    @Override
    public void entryAdded(EntryEvent entryevent) {
        System.out.println("EmailManager add");
    }
    @Override
    public void entryDeleted(EntryEvent entryevent) {
        System.out.println("EmailManager del");
    }
    @Override
    public void entryModified(EntryEvent entryevent) {
        System.out.println("EmailManager modify");
    }
}

package cn.majingjing.tzx.event;
import java.io.IOException;
import java.util.Properties;
public class PropertyMgr {
    private static Properties props = new Properties();
    static {
        try {
            props.load(PropertyMgr.class.getClassLoader().getResourceAsStream("cn/majingjing/tzx/event/config.properties"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static String getProperty(String key) {
        return props.getProperty(key);
    }
}

配置文件 config.properties

observers=cn.majingjing.tzx.event.manager.IndexManager,cn.majingjing.tzx.event.manager.ScoreManager,cn.majingjing.tzx.event.manager.EmailManager

单元测试代码

package cn.majingjing.tzx;
import cn.majingjing.tzx.event.Entry;
import cn.majingjing.tzx.event.manager.EntryManager;
public class Test {
    public static void main(String[] args) {
        EntryManager eventManager = new EntryManager();
        Entry entry = new Entry();
        entry.setId(1);
        entry.setName("test");
        eventManager.addEntry(entry);
        eventManager.modifyEntry(entry);
        eventManager.deleteEntry(entry);
    }
}

源代码： Java观察者模式（Java事件监听）