一个统一管理的例子，用观察者模式实现

如有这么一个需求
 

平台中需要实现一个统一管理的功能 

实现方式1：

平台中定义类 CommonQuery.java ，且有Map<key,Object> 如 put(1,new Query1())
个子类都注册 CommonQuery

在平台中执行的时候 ，会根据Map的值遍历 ,然后调用个子系统的方法


实现方式2：
采用观察者模式

示例代码如下：

QueryMain.java

package test02;

import java.util.ArrayList;
import java.util.List;
import java.util.Observable;

public class QueryMain extends Observable
{

    private static QueryMain instance;

    public static QueryMain getInstance()
    {
        if (instance == null)
        {
            instance = new QueryMain();
        }
        return instance;

    }

    private QueryMain()
    {

    }

    private String starTime;
    /**
     * 查询的结果
     */
    private List<String> listAll = new ArrayList<String>();

    /**
     * 
     * 查询的参数
     * 
     * @param startTime
     * @author 
     * @date 2013-1-11 上午06:14:20
     */
    public void doQuery(String startTime)
    {
        this.starTime = startTime;
        this.listAll = new ArrayList<String>();
        this.setChanged();
        this.notifyObservers();
    }

    /**
     * @return the starTime
     */
    public String getStarTime()
    {
        return starTime;
    }

    /**
     * @param starTime
     *            the starTime to set
     */
    public void setStarTime(String starTime)
    {
        this.starTime = starTime;
    }

    /**
     * @return the listAll
     */
    public List<String> getListAll()
    {
        return listAll;
    }

    /**
     * @param listAll
     *            the listAll to set
     */
    public void setListAll(List<String> listAll)
    {
        this.listAll = listAll;
    }

}

AbsQuery.java

package test02;

import java.util.Observable;
import java.util.Observer;

public abstract class AbsQuery extends Observable implements Observer
{

    @Override
    public void update(Observable o, Object arg)
    {
        doQuery((QueryMain) o);
    }

    public abstract void doQuery(QueryMain queryMain);

}

Query01.java

package test02;


public class Query01 extends AbsQuery
{

    @Override
    public void doQuery(QueryMain queryMain)
    {
        // System.out.println("Query01 doQuery :" + queryMain.getStarTime());

        queryMain.getListAll().add("Query01....1");
        queryMain.getListAll().add("Query01....2");
        queryMain.getListAll().add("Query01....3");

    }

}

Query02.java

package test02;


public class Query02 extends AbsQuery
{

    @Override
    public void doQuery(QueryMain queryMain)
    {
        // System.out.println("Query02 doQuery :" + queryMain.getStarTime());

        queryMain.getListAll().add("Query02....1");
        queryMain.getListAll().add("Query02....2");
        queryMain.getListAll().add("Query02....3");

    }

}

Test.java

package test02;

public class Test
{
    public static void main(String[] args)
    {
        QueryMain queryMain = QueryMain.getInstance();

        Query01 query01 = new Query01();
        Query02 query02 = new Query02();

        queryMain.addObserver(query01);
        queryMain.addObserver(query02);

        QueryMain.getInstance().doQuery("2013");
        System.out.println("-------------");
        for (String s : queryMain.getListAll())
        {
            System.out.println(s);
        }
        
        QueryMain.getInstance().doQuery("2014");
        System.out.println("-------------");
        for (String s : queryMain.getListAll())
        {
            System.out.println(s);
        }
        
        
        
    }
}