设计模式-命令模式

定义：将“请求”封装成对象，以便使用不同的请求、队列或者日志来参数化其他对象。命令模式也支持可撤销的操作。

UML图：

//定义命令接口
public interface Command {

    public void execute();
    
    public void undo();
    
}
//动作接收者
public class Receiver {

    public void open(){
        System.out.println("receiver open");
    }
    
    public void close(){
        System.out.println("receiver close");
    }
}

//实现命令接口
public class ConcreteCommand implements Command{

    private Receiver mRec = null;
    public  ConcreteCommand(Receiver rec) {
        // TODO Auto-generated constructor stub
        mRec = rec;
    }
    @Override
    public void execute() {
        // TODO Auto-generated method stub
        mRec.open();
    }

    @Override
    public void undo() {
        // TODO Auto-generated method stub
        mRec.close();
    }

}
//调用者
public class Invoker {

    Command mCommand = null;
    
    public void setCommand(Command com){
        mCommand = com;
    }
    
    public void execute(){
        if(mCommand != null){
            mCommand.execute();
        }
    }
    
    public void undo(){
        if(mCommand != null){
            mCommand.undo();
        }
    }
}
//客户端
public class Client {

    public static void main(String[] args) {
        Invoker invoker = new Invoker();
        Receiver rec = new Receiver();
        ConcreteCommand concreteCommand = new ConcreteCommand(rec);
        invoker.setCommand(concreteCommand);
        invoker.execute();
        invoker.undo();
    }
}