手撕设计模式——智能家居平台之外观模式
1.业务需求
大家好，我是菠菜啊，好久不见，今天给大家带来的是——外观模式。老规矩，在介绍这期内容前，我们先来看看这样的需求：在智能家居平台中，用户怎么样实现场景化操作（如“回家模式”“睡眠模式”）？
2.代码实现
Talk is cheap，show me your code.
初版实现思路：
我们直接调用多个子设备，实现回家模式的场景化需求。
初版代码如下：
//家居设备基础接口
public interface HomeDevice {
String getName();
String getStatus();
}//灯光设备
public class LightDevice implements HomeDevice{
private String name;
private int brightness=0;
public LightDevice(String name){
name = name;
}
public void dim(int level) {
brightness = level;
System.out.println("灯光调暗至 " + level + "%");
}
public void onLight(){
System.out.println("打开灯光");
brightness = 100;
}
public void offLight(){
System.out.println("关闭灯光");
brightness = 0;
}
@Override
public String getName() {
return name;
}
@Override
public String getStatus() {
return "灯光"+ brightness + "%";
}
}//电视设备
public class TVDevice implements HomeDevice{
private String name;
private String status;
public TVDevice(String name){
name = name;
}
public void onTV(){
System.out.println("打开TV");
status = "on";
}
public void offTV(){
System.out.println("关闭TV");
status = "off";
}
@Override
public String getName() {
return name;
}
@Override
public String getStatus() {
return status;
}
}//空调设备
public class AirCondition implements HomeDevice{
private String name;
private String status;
public AirCondition(String name){
name = name;
}
public void startCooling(){
System.out.println("空调制冷");
status = "cooling";
}
public void off() {
System.out.println("空调关机");
status = "off";
}
@Override
public String getName() {
return name;
}
@Override
public String getStatus() {
return status;
}
}//客户端
public class Client {
public static void main(String[] args) {
LightDevice light = new LightDevice("Light");
TVDevice tv = new TVDevice("TV");
AirCondition ac = new AirCondition("AC");
System.out.println("-----------------HomeModel start-----------------");
light.onLight();
tv.onTV();
ac.startCooling();
System.out.println("-----------------HomeModel end-----------------");
}
}执行结果：
思考：
上述代码我们也发现一些问题，如客户端（用户）切换到回家模式的时候，需要自行完成三个子设备的调用，用户需要关心这么多细节吗？这样耦合性是不是太强了？于是，我们又经过一系列优化。
3.代码优化
优化代码：
//智能家居外观类
public class SmartHomeFacade {
private LightDevice lightDevice;
private TVDevice tvDevice;
private AirCondition airCondition;
public SmartHomeFacade() {
lightDevice = new LightDevice("Light");
tvDevice = new TVDevice("TV");
airCondition = new AirCondition("AirCondition");
}
public void activeHomeModel() {
System.out.println("-----------------activeHomeModel start-----------------");
lightDevice.onLight();
tvDevice.onTV();
airCondition.startCooling();
System.out.println("-----------------activeHomeModel end-----------------");
System.out.println("deviceName:"+lightDevice.getName()+",status:"+lightDevice.getStatus());
System.out.println("deviceName:"+tvDevice.getName()+",status:"+tvDevice.getStatus());
System.out.println("deviceName:"+airCondition.getName()+",status:"+airCondition.getStatus());
}
}//客户端
public class Client {
public static void main(String[] args) {
/* LightDevice light = new LightDevice("Light");
TVDevice tv = new TVDevice("TV");
AirCondition ac = new AirCondition("AC");
System.out.println("-----------------HomeModel start-----------------");
light.onLight();
tv.onTV();
ac.startCooling();
System.out.println("-----------------HomeModel end-----------------");*/
SmartHomeFacade smartHomeFacade = new SmartHomeFacade();
smartHomeFacade.activeHomeModel();
}
}执行结果：
代码结构：
思考：
用户无需要知道所有设备的调用细节，只需简单调用SmartHomeFacade的activeHomeModel方法，实现真正意义上的一键切换回家模式。如果调用逻辑修改或者添加新设备了，客户端无感知，进一步降低耦合，符合迪米特法则。
4.定义与组成
定义：
外观模式（Facade Pattern）是一种结构型设计模式，它提供了一个统一的接口，用于访问子系统中的一组接口。外观模式定义了一个高层接口，这个接口使得子系统更容易使用。
组成：
- 外观（Facade）：提供统一的调用接口，将客户端请求委派给适当的子系统对象
- 子系统（SubSystem）：实现具体功能，被外观类调用
核心思想
封装复杂性，提供简单接口
通过创建一个简化的高层接口，隐藏子系统的实现细节，降低客户端与子系统的耦合度。
5.代码重构（工厂模式+抽象外观模式）
思考：
上述的代码实现依赖外观类，不够抽象，而且新增家居设备需要修改外观类，而且不支持动态扩展场景,所以了解了问题后我们进一步重构了代码。
代码重构：
//抽象智能家居外观接口
public interface ISmartHomeFacade {
//切换到回家模式
void activeHomeModel();
//切换到睡眠模式
void activateSleepMode();
// 扩展点：动态添加设备
void addDevice(String deviceName, HomeDevice device);
// 获取设备
<T extends HomeDevice> T getDevice(Class<T> deviceClass);
}//动态智能家居外观类
public class DynamicSmartHomeFacade implements ISmartHomeFacade{
private final Map<String, HomeDevice> devices = new HashMap<>();
public DynamicSmartHomeFacade() {
addDevice("Light",new LightDevice("Light"));
addDevice("TV",new TVDevice("TV"));
addDevice("AirCondition",new AirCondition("AirCondition"));
}
@Override
public void activeHomeModel() {
System.out.println("-----------------activeHomeModel start-----------------");
getDevice(LightDevice.class).onLight();
getDevice(TVDevice.class).onTV();
getDevice(AirCondition.class).startCooling();
System.out.println("-----------------activeHomeModel end-----------------");
}
// 泛型方法获取设备
@SuppressWarnings("unchecked")
public <T extends HomeDevice> T getDevice(Class<T> deviceClass) {
return devices.values().stream()
.filter(deviceClass::isInstance)
.map(device -> (T) device)
.findFirst()
.orElseThrow(() -> new RuntimeException(
"Device not found: " + deviceClass.getSimpleName()));
}
public boolean hasDevice(Class<? extends HomeDevice> deviceClass) {
return devices.values().stream()
.anyMatch(deviceClass::isInstance);
}
@Override
public void activateSleepMode() {
System.out.println("-----------------activateSleepMode start-----------------");
getDevice(LightDevice.class).dim(10);
getDevice(TVDevice.class).offTV();
getDevice(AirCondition.class).startCooling();
System.out.println("-----------------activateSleepMode end-----------------");
}
@Override
public void addDevice(String deviceName, HomeDevice device) {
devices.put(deviceName, device);
}
}//抽象场景工厂接口
public interface ISceneFactory {
SmartHomeScene createScene();
}//离家模式创建工厂
public class AwayHomeISceneFactory implements ISceneFactory {
@Override
public SmartHomeScene createScene() {
return new SmartHomeScene("离家模式",(facade->{
System.out.println("-----------------activeAwayHomeModel start-----------------");
facade.getDevice(LightDevice.class).offLight();
facade.getDevice(TVDevice.class).offTV();
facade.getDevice(AirCondition.class).off();
System.out.println("-----------------activeAwayHomeModel end-----------------");
}));
}
}//场景管理
public class SceneManager {
private final Map<String, ISceneFactory> sceneFactories = new HashMap<>();
private final ISmartHomeFacade facade;
public SceneManager(ISmartHomeFacade facade) {
this.facade = facade;
}
public void registerScene(String name, ISceneFactory factory) {
sceneFactories.put(name, factory);
}
public void activateScene(String name) {
ISceneFactory factory = sceneFactories.get(name);
if(factory != null) {
SmartHomeScene scene = factory.createScene();
scene.execute(facade);
}
}
}//动态场景类
public class SmartHomeScene {
private final String sceneName;
private final Consumer<ISmartHomeFacade> sceneExecutor;
public SmartHomeScene(String sceneName, Consumer<ISmartHomeFacade> sceneExecutor) {
this.sceneName = sceneName;
this.sceneExecutor = sceneExecutor;
}
public void execute(ISmartHomeFacade facade) {
sceneExecutor.accept(facade);
}
}//智能床设备
public class SmartBedDevice implements HomeDevice{
private String name;
private int angle=0;
public SmartBedDevice(String name){
name = name;
}
public void adjust(int angle) {
angle = angle;
System.out.println("智能床调至 " + angle + "角度");
}
@Override
public String getName() {
return name;
}
@Override
public String getStatus() {
return "智能床"+ angle + "角度";
}
}//客户端
public class Client2 {
public static void main(String[] args) {
DynamicSmartHomeFacade facade = new DynamicSmartHomeFacade();
// 开启回家模式
facade.activeHomeModel();
// 添加智能床设备
facade.addDevice("SmartBed", new SmartBedDevice("SmartBed"));
// 开启睡眠模式
facade.activateSleepMode();
ISceneFactory factory = new AwayHomeISceneFactory();
SceneManager sceneManager = new SceneManager(facade);
sceneManager.registerScene("离家模式", factory);
sceneManager.activateScene("离家模式");
}
}上述代码执行结果：
实现代码结构：
总结：
上述代码通过抽象外观接口，通过addDevice()方法添加，无需修改外观类，通过SceneManager动态注册场景工厂新增场景，实现设备热插拔以及场景热部署。这种基于抽象接口的外观模式实现，不仅遵循了开闭原则，还为智能家居系统提供了强大的扩展能力。通过动态设备管理和场景工厂等机制，系统可以在不修改核心代码的情况下持续演进，完美适应快速变化的智能家居生态。
6.应用示例
其实外观模式我们在日常开发的时候应用的很广泛，下面是一些示例：
6.1日志框架：
// SLF4J是典型的外观模式实现
Logger logger = LoggerFactory.getLogger(MyClass.class);
logger.info("This is a log message");6.2 Spring框架：
// JdbcTemplate封装了JDBC的复杂性
jdbcTemplate.query("SELECT * FROM users", new BeanPropertyRowMapper<>(User.class));6.3 Files类
// Files类封装了文件操作的复杂性
Files.copy(source, target, StandardCopyOption.REPLACE_EXISTING);7.适用场景
| 场景类型 | 是否适用 | 原因 |
|---|---|---|
| 系统复杂且模块多 | ✅ 非常适用 | 简化客户端调用 |
| 需要解耦客户端与子系统 | ✅ 推荐使用 | 降低依赖关系 |
| 需要为子系统提供统一入口 | ✅ 理想选择 | 提供简洁接口 |
| 需要逐步重构遗留系统 | ✅ 适用 | 作为中间层 |
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