java sendcommand_命令模式-Command(Java实现)

命令模式-Command

将一个命令请求封装为一个对象, 这样就可以使用命令来修改目标对象的相关参数了.

本文的例子是, 狗主人(Master) 希望对狗狗发一些命令, 狗来进行响应, 以达到修改"参数"的作用.

比如, 发出让狗狗坐下, 吐舌头 等命令后...狗狗的参数就从站着变为了坐着, 从没伸出舌头变为了吐出舌头.

HandState枚举

public enum HandState {

REACH("伸出爪子"), BACK("没伸出爪子");

private String handState;

HandState(String handState) {

this.handState = handState;

}

@Override

public String toString() {

return handState;

}

}

PostureState枚举

public enum PostureState {

SITTING("坐着"), STANDING("站着");

private String posture;

PostureState(String posture) {

this.posture = posture;

}

@Override

public String toString() {

return posture;

}

}

TongueState枚举

public enum TongueState {

SPIT("吐出舌头"), BACK("没伸出舌头");

private String tongueState;

TongueState(String tongueState) {

this.tongueState = tongueState;

}

@Override

public String toString() {

return tongueState;

}

}

Command接口

命令的抽象定义.

public interface Command {

/**

* 对dog执行命令

*/

void execute(Dog dog);

/**

* 再来一遍刚刚那次execute(dog)

*/

void undo();

/**

* 撤销刚刚那次execute(dog)

*/

void redo();

@Override

String toString();

}

HandStateCommand类

握手命令

public class HandStateCommand implements Command {

private Dog dog;

@Override

public void execute(Dog dog) {

dog.setHandState(HandState.REACH);

this.dog = dog;

}

@Override

public void undo() {

if (dog != null) {

dog.setHandState(HandState.BACK);

}

}

@Override

public void redo() {

if (dog != null) {

dog.setHandState(HandState.REACH);

}

}

@Override

public String toString() {

return "让狗伸出爪子的命令";

}

}

PostureStateCommand类

站立/坐下姿势命令.

public class PostureStateCommand implements Command {

private Dog dog;

@Override

public void execute(Dog dog) {

dog.setPostureState(PostureState.SITTING);

this.dog = dog;

}

@Override

public void undo() {

if (dog != null) {

dog.setPostureState(PostureState.STANDING);

}

}

@Override

public void redo() {

if (dog != null) {

dog.setPostureState(PostureState.SITTING);

}

}

@Override

public String toString() {

return "让狗坐下的命令";

}

}

TongueStateCommand类

伸舌头/合上嘴 命令

public class TongueStateCommand implements Command {

private Dog dog;

@Override

public void execute(Dog dog) {

dog.setTongueState(TongueState.SPIT);

this.dog = dog;

}

@Override

public void undo() {

if (dog != null) {

dog.setTongueState(TongueState.BACK);

}

}

@Override

public void redo() {

if (dog != null) {

dog.setTongueState(TongueState.SPIT);

}

}

@Override

public String toString() {

return "让狗吐出舌头的命令";

}

}

Dog类

被命令的对象, 根据命令会改变Dog类的状态.

public class Dog {

private HandState handState;

private PostureState postureState;

private TongueState tongueState;

{

handState = HandState.BACK;

postureState = PostureState.STANDING;

tongueState = TongueState.BACK;

}

public void setHandState(HandState handState) {

this.handState = handState;

}

public void setPostureState(PostureState postureState) {

this.postureState = postureState;

}

public void setTongueState(TongueState tongueState) {

this.tongueState = tongueState;

}

@Override

public String toString() {

return "Dog{" +

"handState=" + handState +

", postureState=" + postureState +

", tongueState=" + tongueState +

'}';

}

public void printStatus() {

System.out.println(this);

}

}

Master类

由Master来施加命令来对Dog进行一些参数上的改变.

import java.util.Deque;

import java.util.LinkedList;

public class Master {

private Deque undoStack = new LinkedList<>();

private Command redo ;

public Master() {

}

public void sendCommand(Command command, Dog dog) {

System.out.printf("主人使用命令:\n", command);

command.execute(dog);

redo = command;

undoStack.offerLast(command);

}

public void undoLastCommand() {

if (!undoStack.isEmpty()) {

Command previousSpell = undoStack.pollLast();

redo = previousSpell;

System.out.printf("主人撤回命令:\n", previousSpell);

previousSpell.undo();

}

}

public void redoLastCommand() {

if (redo!=null) {

undoStack.offerLast(redo);

System.out.printf("再一次执行了命令:\n", redo);

redo.redo();

}

}

@Override

public String toString() {

return "狗的主人";

}

}

Main

运行程序/ 场景模拟

public class Main {

public static void main(String[] args) {

Master master = new Master();

Dog dog = new Dog();

dog.printStatus();

//开始命令狗, 站姿坐姿

master.sendCommand(new PostureStateCommand(), dog);

dog.printStatus();

// 开始命令狗, 吐舌头

master.sendCommand(new TongueStateCommand(), dog);

dog.printStatus();

master.redoLastCommand();

dog.printStatus();

master.undoLastCommand();

dog.printStatus();

master.redoLastCommand();

dog.printStatus();

master.undoLastCommand();

dog.printStatus();

// 开始命令狗, 伸爪子

master.sendCommand(new HandStateCommand(), dog);

dog.printStatus();

master.redoLastCommand();

dog.printStatus();

master.undoLastCommand();

dog.printStatus();

}

}

运行结果如下: