设计模式简述（九）命令模式

描述

命令模式是一种体现高内聚的行为模式。
将整个请求封装成一个命令对象，由这个命令对象完成所需业务调用。
命令对象封装了该命令需要的所有逻辑，不需要调用方关注内部细节。

组件

• 定义抽象命令（所有命令都基于这个抽象命令定义）

public abstract class AbstractCommand {
    abstract void execute();
}

• 定义命令对象内要实际调用的业务对象

public interface IReceiver {
    void action();
}

public class ReceiverA implements IReceiver {
    @Override
    public void action() {
        System.out.println("ReceiverA action ....");
    }
}

public class ReceiverB implements IReceiver {
    @Override
    public void action() {
        System.out.println("ReceiverB action ....");
    }
}

• 定义两个具体的命令

public class CommandA extends AbstractCommand{
    private IReceiver receiver;

    public CommandA(IReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    void execute() {
        System.out.println("commandA....");
        receiver.action();
    }
}

public class CommandAB extends AbstractCommand{
    private IReceiver[] receivers;

    public CommandAB(IReceiver... receivers) {
        this.receivers = receivers;
    }

    @Override
    void execute() {
        System.out.println("commandA....");
        for (IReceiver receiver : receivers) {
            receiver.action();
        }
    }
}

使用

public class Sample {
    public static void main(String[] args) {
        IReceiver receiverA = new ReceiverA();
        IReceiver receiverB = new ReceiverB();
        AbstractCommand command = new CommandA(receiverA);
        command.execute();
        AbstractCommand commandAb = new CommandAB(receiverA, receiverB);
        commandAb.execute();
    }
}