4.设计模式之命令模式

命令模式：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
SpringMVC中HandlerMapping方法中HandlerExecutionChain getHandler(HttpServletRequest request)便是典型的Command模式的使用

1. 命令接口定义

public interface Command {
    
    
    void execute();
}

2. 遥控器类组合命令

public class SimpleRemoteControl {
    
    
    private Command slot;

    public SimpleRemoteControl() {
    
    };

    public void setCommand(Command command) {
    
    
        slot = command;
    }

    public void buttonWasPressed() {
    
    
        slot.execute();
    }

}

3. 开灯命令

public class LightOnCommand implements Command {
    
    
    private Light light;

    public LightOnCommand() {
    
    };

    public LightOnCommand(Light light) {
    
    
        this.light = light;
    }

    @Override
    public void execute() {
    
    
        light.on();
    }
}

其中Light.java为：

public class Light {
    
    
    private String roomName;

    public Light() {
    
    };

    public Light(String roomName) {
    
    
        this.roomName = roomName;
    }

    public void on() {
    
    
        System.out.println(roomName + "light is on");
    }

    public void off() {
    
    
        System.out.println(roomName + "light is off");
    }
}

4. 测试

public class ComplexCommandTest {
    
    

    @Test
    public void testParameterCommand() {
    
    
        Light light = new Light("Living Room");
        Command lightOnCommand = new LightOnCommand(light);
        
        SimpleRemoteControl control = new SimpleRemoteControl();

        control.setCommand(lightOnCommand);
        control.buttonWasPressed();
    }
}

5. 输出

Living Roomlight is on