命令模式(行为型)

命令模式

    将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化；对请求排队或记录请求日志，以及支持可撤消的操作。

 适用性

    1.抽象出待执行的动作以参数化某个对象。

    2.在不同的时刻指定、排列和执行请求。

    3.支持取消操作。

    4.支持修改日志，这样当系统崩溃时，修改可以被重做一遍。

    5.用构建在原语操作上的高层操作构造一个系统。

结构类图

headfirst结构类图

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系统结构图

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抽象命令

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public interface Command {public void execute();}

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具体命令

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public class DoorOffCommand implements Command {private Door door;public DoorOffCommand(Door door) {this.door = door;}@Overridepublic void execute() {// TODO Auto-generated method stubdoor.doorOff();}}public class DoorOnCommand implements Command{private Door door;public DoorOnCommand(Door door) {this.door = door;}@Overridepublic void execute() {// TODO Auto-generated method stubdoor.doorOn();}}public class LightOffCommand implements Command {private Light light;public LightOffCommand(Light light) {this.light = light;}@Overridepublic void execute() {// TODO Auto-generated method stublight.lightOff();}}public class LightOnCommand implements Command{private Light light;public LightOnCommand(Light light) {this.light = light;}@Overridepublic void execute() {// TODO Auto-generated method stublight.lightOn();}}

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命令控制器

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public class SimpleRemoteControl {private Command[] onCommand;private Command[] offCommand;private Command undocommand;public SimpleRemoteControl(){onCommand=new Command[2];offCommand=new Command[2];}public void setCommand(int slot,Command onCommand,Command offCommand){this.onCommand[slot]=onCommand;this.offCommand[slot]=offCommand;}public void buttonDoPress(int slot){onCommand[slot].execute();undocommand=onCommand[slot];}public void buttonOffDoPress(int slot){offCommand[slot].execute();undocommand=onCommand[slot];}public void unDoCommand(){undocommand.execute();}}

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命令执行者

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public class Door {public Door(){}public void doorOff(){System.out.println("Door off");}public void doorOn(){System.out.println("Door on");}}public class Light {public Light(){}public void lightOn(){System.out.println("light on");}public void lightOff(){System.out.println("light off");}}

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客户

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public class TestClient {public static void main(String[] args) {Door door=new Door();Light light=new Light();Command command=new DoorOffCommand(door);Command command2=new DoorOnCommand(door);Command command3=new LightOffCommand(light);Command command4=new LightOnCommand(light);SimpleRemoteControl simpleRemoteControl =new SimpleRemoteControl();simpleRemoteControl.setCommand(0, command, command2);simpleRemoteControl.setCommand(1, command3, command4);System.out.println("--------------");simpleRemoteControl.buttonDoPress(0);simpleRemoteControl.buttonOffDoPress(0);simpleRemoteControl.unDoCommand();System.out.println("--------------");simpleRemoteControl.buttonDoPress(1);simpleRemoteControl.buttonOffDoPress(1);simpleRemoteControl.unDoCommand();System.out.println("--------------");}}

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执行结果

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--------------Door offDoor onDoor off--------------light offlight onlight off--------------