自己動手實現-監聽器

監聽器就是在執行一些操作的時候通知監聽此事件的對象執行一定的方法。

寫了BingoneMap，其中使用Set存儲監聽器，在事件發生後執行監聽器事件。基本要素是留一個口子給開發者實現該事件需執行怎麼的操作。

同時注意數據之間的傳遞，監聽器方法和調用者之間的數據交互。

package bingone;

import java.util.*;

/**
 * Created by bingone on 16/3/21.
 */
public class BingoneMap<K, V> {
    private Map<K, V> data = new HashMap<K, V>();
    private Set<BingoneMapListener> listeners = new LinkedHashSet<BingoneMapListener>();

    public V get(K key) {
        for (BingoneMapListener b : listeners) {
            b.commonJob(new BingoneMapListener.Event(key, BingoneMapListener.EnumEvent.GET));
        }
        System.out.println("Listener has been done");
        return null == key ? null : data.get(key);
    }

    public void put(K key, V value) {
        for (BingoneMapListener b : listeners) {
            b.commonJob(new BingoneMapListener.Event(key, BingoneMapListener.EnumEvent.PUT));
        }
        System.out.println("Listener has been done");
        data.put(key, value);
    }

    public void addListener(BingoneMapListener bingoneMapListener) {
        this.listeners.add(bingoneMapListener);
    }


    public static abstract class BingoneMapListener<T> {

        public T retData;

        public BingoneMapListener(T retData) {
            this.retData = retData;
        }

        public void commonJob(Event event) {
            System.out.println("now in " + this);
            myJob(event);
            System.out.println("now out " + this);
        }

        public abstract T myJob(Event event);

        public static class Event<E> {
            public E inputData;
            public EnumEvent enumEvent;

            public Event(E inputData, EnumEvent e) {
                this.inputData = inputData;
                this.enumEvent = e;
            }


        }


        public enum EnumEvent {
            PUT(), GET();
        }
    }

    public static void main(String... args) {
        BingoneMap<String, String> bm = new BingoneMap<String, String>();
        final StringBuilder sb = new StringBuilder();
        bm.addListener(new BingoneMapListener(sb) {
            @Override public Object myJob(Event event) {
                System.out.println("in listener");
                if (event.enumEvent == EnumEvent.GET) {
                    System.out.println("get " + event.inputData + " at " + System.currentTimeMillis());
                    sb.append("get");
                } else if (event.enumEvent == EnumEvent.PUT) {
                    System.out.println("put " + event.inputData + " at " + System.currentTimeMillis());
                    sb.append("put");
                }
                return "success";
            }
        });
        bm.put("a", "b");
        bm.get("a");
        System.out.println(sb.toString());
    }
}