门面模式-Facade Pattern(Java实现)

门面模式-Facade Pattern

为一个复杂的模块或子系统提供一个简单的供外界访问的接口

本文中代码的例子如下: 一个矿场有很多矿工, 矿工的职责也都不一样. 但一样的是什么呢? 一样的就是每个矿工每天都在重复一样的事情....起床, 上班, 工作, 下班, 睡觉......

要想管理这么多矿工的这么多事情可不简单(好麻烦啊...挨个调用的时候开发者也有可能会忘掉某个人, 或者忘掉某一个方法).,

 

再举个栗子, 比如操作数据库也一样, 要加载驱动, 建立连接, 操作数据库, 关闭连接. 这么多步骤忘掉一个都会是个问题.

MineWorker抽象类

这里是矿场中工人的统一抽象定义.

public abstract class MineWorker {
    protected void goToSleep() {
        System.out.printf("%s 睡觉.\n", name());
    }

    protected void wakeUp() {
        System.out.printf("%s 早上醒过来.\n", name());
    }

    protected void goHome() {
        System.out.printf("%s 回家.\n", name());
    }

    protected void goToMine() {
        System.out.printf("%s 去矿场.\n", name());
    }

    protected abstract void work();

    protected abstract String name();

    public static enum Action {
        GO_TO_SLEEP, WAKE_UP, GO_HOME, GO_TO_MINE, WORK
    }

    public void action(Action... actions) {
        for (Action action : actions) {
            switch (action) {
                case GO_TO_SLEEP:
                    goToSleep();
                    break;
                case WAKE_UP:
                    wakeUp();
                    break;
                case GO_HOME:
                    goHome();
                    break;
                case GO_TO_MINE:
                    goToMine();
                    break;
                case WORK:
                    work();
                    break;
                default:
                    System.out.println("Undefined action");
                    break;
            }
        }
    }
}

CartOperator类

推车工人.

public class CartOperator extends MineWorker {
    @Override
    public void work() {
        System.out.printf("%s 运输矿石 \n", name());
    }

    @Override
    public String name() {
        return "推车工人";
    }
}　　

GoldDigger类

挖金矿工人

public class GoldDigger extends MineWorker {

    @Override
    public void work() {
        System.out.printf("%s 挖金矿 .\n", name());
    }

    @Override
    public String name() {
        return "挖矿金工人";
    }
}

TunnelDigger类

挖隧道工人.

public class TunnelDigger extends MineWorker {

    @Override
    public void work() {
        System.out.printf("%s 挖隧道.\n", name());
    }

    @Override
    public String name() {
        return "挖隧道工人";
    }
}

MineFacade类

本系统的门面, 用于对外提供一个简单的接口.

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class MineFacade {

    private final List<MineWorker> mineWorkers;

    public MineFacade() {
        mineWorkers = new ArrayList<>();
        mineWorkers.add(new GoldDigger());
        mineWorkers.add(new CartOperator());
        mineWorkers.add(new TunnelDigger());
    }

    public void startNewDay() {
        makeActions(mineWorkers, MineWorker.Action.WAKE_UP, MineWorker.Action.GO_TO_MINE);
    }

    public void digOutGold() {
        makeActions(mineWorkers, MineWorker.Action.WORK);
    }

    public void endDay() {
        makeActions(mineWorkers, MineWorker.Action.GO_HOME, MineWorker.Action.GO_TO_SLEEP);
    }

    private static void makeActions(Collection<MineWorker> mineWorkers,
                                    MineWorker.Action... actions) {
        for (MineWorker mineWorker : mineWorkers) {
            mineWorker.action(actions);
        }
    }
}

Main

在这运行

public class Main {
    public static void main(String[] args) {
        // 实例化一个门面, 这是矿场对外提供的一个简单的接口
        MineFacade mineFacade = new MineFacade();

        // 开始新的一天
        mineFacade.startNewDay();

        // 大家起来干活
        mineFacade.digOutGold();

        // 一天结束啦
        mineFacade.endDay();
    }
}

运行结果如下: