1. 定義一個統一的回撥介面

public interface CallerInter {
    void call(Param param);
}

public interface ObserverInter{
    /**
     * 增加觀察者
     *
     * @param callInter
     */
    void addObserver(CallerInter callInter);

    /**
     * 刪除觀察者
     *
     * @param lemmaWriteBackOpObserver
     */
    void delObserver(CallerInter callInter);

    /**
     * 通知觀察者
     *
     * @param lemmaRecord
     */
    void notifyAllObserver(Param param);
}
 

import org.springframework.beans.factory.InitializingBean;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * Created by denglinjie on 2016/8/19.
 */
@Service
public class ObserverImpl implements ObserverInter, InitializingBean {

    //要通知的物件列表
    private List<CallerInter> callerInterList;

    public void addObserver(CallerInter callInter) {
        callerInterList.add(callInter);
    }

    public void delObserver(CallerInter callInter) {
        callerInterList.remove(callInter);
    }

    public void notifyAllObserver(Param param) {
        for(CallerInter callerInter : callerInterList) {
            callerInter.call(param);
        }
    }

    public void afterPropertiesSet() throws Exception {
        callerInterList = new CopyOnWriteArrayList<CallerInter>();  //這裡用一個執行緒安全的list，因為可能多執行緒同時操作它
    }

    /**
     * 對外提供一個介面，當這個介面被呼叫的時候，可以通知所有註冊進來的物件的特定call介面
     */
    public void operateService() {
        //構造引數
        Param param = new Param();
        notifyAllObserver(param);
    }
}
 

import com.sogou.study.observer.CallerInter;
import com.sogou.study.observer.ObserverInter;
import com.sogou.study.observer.Param;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;

/**
 * Created by denglinjie on 2016/8/19.
 */
public class CallImplFirst implements CallerInter, InitializingBean {

    @Autowired
    private ObserverInter observerInter;

    public void call(Param param) {
        //do something
    }

    public void afterPropertiesSet() throws Exception {
        observerInter.addObserver(this);
    }
}
 

import com.sogou.study.observer.CallerInter;
import com.sogou.study.observer.ObserverInter;
import com.sogou.study.observer.Param;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;

/**
 * Created by denglinjie on 2016/8/19.
 */
public class CallImplSecond implements CallerInter, InitializingBean {

    @Autowired
    private ObserverInter observerInter;

    public void call(Param param) {
        //do something
    }

    public void afterPropertiesSet() throws Exception {
        observerInter.addObserver(this);
    }
}