## 1. 再谈设计原则html
软件系统的设计, 应对扩展开放, 对修改关闭;
全部基类出现的地方, 均可以被子类替换;
应该依赖于抽象而非具体;
多个专门的接口好于单一的总接口;
使用合成/聚合的方式复用, 而不是继承; 聚合: 更强的合成;
若非必要,不要暴露(最少知道原则);
public class App { // 主业务流程 public void doBusiness(ICallback callback){ System.out.println("主流程工做..."); callback.call(); } } public interface ICallback { void call(); } // 0. 回调操做随主流程执行 @Test void callbackTest() { App app = new App(); app.doBusiness(() -> { System.out.println("回调操做..."); }); }
Subject/OneSubject: 被观察对象(发布者)
Observer: 观察者(订阅者)java
观察者接口(订阅者)算法
/** * 观察者(订阅者) */ public interface Observer { void update(String msg); }
观察者/订阅者1(实现类)spring
/** * 观察者/订阅者1 * @author nieweijun * @since 2021/6/1 22:09 */ public class OneObserver implements Observer{ @Override public void update(String msg) { System.out.println("OneObserver收到消息:["+msg+"]"); } }
观察者实现类2shell
/** * 观察者/订阅者1 * @author nieweijun * @since 2021/6/1 22:09 */ public class OneObserver implements Observer{ @Override public void update(String msg) { System.out.println("OneObserver收到消息:["+msg+"]"); } }
被观察者设计模式
/** * 被观察者(主题/发布者) */ public interface Subject { void addObserver(Observer observer); void removeObserver(Observer observer); void notifyObservers(); }
被观察者实现api
/** * 主题/发布者实现 * @author nieweijun * @since 2021/6/1 22:12 */ public class OneSubject implements Subject{ Vector<Observer> observers = null; public OneSubject(){ this.observers = new Vector<>(); } @Override public void addObserver(Observer observer) { observers.addElement(observer); } @Override public void removeObserver(Observer observer) { observers.removeElement(observer); } @Override public void notifyObservers() { for (Observer observer : observers) { observer.update("雷阵雨~"); } } }
测试调用:数据结构
// 1.普通观察者 @Test void myObserverTest() { // 1.被观察者(主题) OneSubject subject = new OneSubject(); // 2.观察者1(订阅者1) OneObserver obs1 = new OneObserver(); // 3.观察者2(订阅者2) TwoObserver obs2 = new TwoObserver(); // 注册观察者 subject.addObserver(obs1); subject.addObserver(obs2); // 发布消息(通知全部观察者) subject.notifyObservers(); }
OneObserver收到消息:[雷阵雨~] TwoObserver收到消息:[雷阵雨~]
Observable/MySubject: 被观察对象(发布者)
Observer: 观察者(订阅者)app
jdk中的发布者实现类(被观察者)异步
import java.util.Observable; /** * JDK内置的观察者模式用例 * @author nieweijun * @since 2021/5/31 18:13 */ @Slf4j public class WeatherObservable extends Observable { @Override public String toString() { return "布谷天气"; } @Override public synchronized void setChanged() { super.setChanged(); } }
测试用例调用
// 2. jdk观察者 @Test void weatherReportTest() { WeatherObservable obs = new WeatherObservable(); // 主题 // A obs.addObserver((o, arg) -> log.info("订阅者-A收到[{}]发布的消息:{}", o, arg)); // B obs.addObserver((o, arg) -> log.info("订阅者-B收到消息[{}]发布的消息:{}", o, arg)); // C obs.addObserver((o, arg) -> log.info("订阅者-C收到[{}]发布的消息:{}", o, arg)); obs.setChanged(); obs.notifyObservers("今日北京雷阵雨"); }
输出:
PatternObserverTest - 订阅者-C收到[布谷天气]发布的消息:今日北京雷阵雨 PatternObserverTest - 订阅者-B收到消息[布谷天气]发布的消息:今日北京雷阵雨 PatternObserverTest - 订阅者-A收到[布谷天气]发布的消息:今日北京雷阵雨
注意: 观察者的实现用FunctionalInterface实现了, 3个观察者;
按钮监听事件案例:
import javax.swing.*; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; /** * java GUI 观察者(监听器) * @author nieweijun * @since 2021/6/1 22:21 */ public class GuiObserver { public GuiObserver() { JFrame jFrame = new JFrame("HelloButton"); // 1. button 事件源 JButton btn = new JButton("click me~"); // 2. 事件监听器(携带监听事件 ActionEvent) ActionListener myListener = new ActionListener() { @Override public void actionPerformed(ActionEvent e) { JOptionPane.showMessageDialog(null, "按钮被点击!"); } }; // 3. 注册事件 btn.addActionListener(myListener); // btn.addActionListener((e) -> JOptionPane.showMessageDialog(null, "按钮被点击!")); jFrame.add(btn); jFrame.setLayout(new FlowLayout()); jFrame.setSize(500,400); jFrame.setLocation(400, 400); jFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); jFrame.setVisible(true); } public static void main(String[] args) { new GuiObserver(); } }
案例: 回家事件; 两个实现(一个是工做日回家; 一个是节假日回家; 输出信息不同)
import java.util.EventObject; /** * 事件:(通常潜藏于Listener) * @author nieweijun * @since 2021/6/9 9:49 */ public class HomeEvent extends EventObject { @Setter @Getter private String type; public HomeEvent(Object source, String type){ super(source); this.type = type; } /** * @param source 事件源 * @throws IllegalArgumentException */ public HomeEvent(Object source) { super(source); } }
定义本身的回调接口, 拉上事件作参数
import java.util.EventListener; /** * 回家事件监听器 * @author nieweijun * @since 2021/6/9 9:53 */ public interface HomeListener extends EventListener { void onHomeEvent(HomeEvent event); }
import lombok.extern.slf4j.Slf4j; /** * 节假日回家事件 * @author nieweijun * @since 2021/6/9 9:56 */ @Slf4j public class HolidayHomeListener implements HomeListener { @Override public void onHomeEvent(HomeEvent event) { if (event.getType().equals("holiday")) { log.info("@===============> HolidayHomeListener#onHomeEvent:放假回家, 开开心心的! type={}", event.getType()); } } }
import lombok.extern.slf4j.Slf4j; /** * 工做日回家事件 * @author nieweijun * @since 2021/6/9 9:56 */ @Slf4j public class WorkdayHomeListener implements HomeListener { @Override public void onHomeEvent(HomeEvent event) { if (event.getType().equals("work")) { log.info("@===============> WorkdayHomeListener#onHomeEvent:工做日回家, 吾日三省吾身了没? type={}", event.getType()); } } }
import java.util.ArrayList; import java.util.Iterator; import java.util.List; /** * 事件发布者 * @author nieweijun * @since 2021/6/9 13:49 */ public class Manager { private List<HomeListener> list; public Manager(){ list = new ArrayList<>(); } public void addListener(HomeListener listener) { if(list == null){ list = new ArrayList<>(); } list.add(listener); } public void removeListener(HomeListener listener) { if(list != null){ list.remove(listener); } } /** * 通知全部的Listener */ private void notifyListeners(HomeEvent event) { for (HomeListener listener : list) { listener.onHomeEvent(event); } } public void holidayGoHome(){ HomeEvent event = new HomeEvent(this, "holiday"); notifyListeners(event); } public void workdayGoHome(){ HomeEvent event = new HomeEvent(this, "work"); notifyListeners(event); } }
注意: 两个方法: holidayGoHome
和 workdayGoHome
两个方法, 作了发布事件的调用, 并触发通知事件(通知全部的监听者)
// 5. 自定义监听器 测试用例 @Test void testListener() { Manager manager = new Manager(); manager.addListener(new HolidayHomeListener()); manager.addListener(new WorkdayHomeListener()); // 工做日回家 manager.workdayGoHome(); // 节假日回家 manager.holidayGoHome(); }
输出:
WorkdayHomeListener - @===============> WorkdayHomeListener#onHomeEvent:工做日回家, 吾日三省吾身了没? type=work HolidayHomeListener - @===============> HolidayHomeListener#onHomeEvent:放假回家, 开开心心的! type=holiday
事件+事件源的做用就是被观察者;
ApplicationEventPublisher
1. 事件:
import lombok.Getter; import org.springframework.context.ApplicationEvent; /** * 观察者 * @author nieweijun * @since 2021/5/31 14:15 */ public class RegisterEvent extends ApplicationEvent { /** * 登陆用户用户名 */ @Getter private String userName; /** * Create a new {@code ApplicationEvent}. * @param source the object on which the event initially occurred or with * which the event is associated (never {@code null}) */ public RegisterEvent(Object source) { super(source); } public RegisterEvent(Object source, String userName) { super(source); this.userName = userName; } }
2. 监听器1:
import lombok.extern.slf4j.Slf4j; import org.springframework.context.ApplicationListener; import org.springframework.stereotype.Service; /** * 发放优惠券 * @author nieweijun * @since 2021/5/31 14:25 */ @Service @Slf4j public class CouponServiceListener implements ApplicationListener<RegisterEvent> { @Override public void onApplicationEvent(RegisterEvent event) { log.info("#=====>[CouponService.onApplicationEvent] 给用户{}发放3张满减新手券! =====#", event.getUserName()); } }
2. 监听器2:
import lombok.extern.slf4j.Slf4j; import org.springframework.context.ApplicationListener; import org.springframework.scheduling.annotation.Async; import org.springframework.stereotype.Service; /** * @author nieweijun * @since 2021/5/31 14:23 */ @Service @Slf4j public class EmailServiceListener implements ApplicationListener<RegisterEvent> { @Async // 异步发邮件 @Override public void onApplicationEvent(RegisterEvent event) { log.info("#=====>[EmailService.onApplicationEvent] 执行发邮件给用户: {} =====# ", event.getUserName()); } }
2. 监听器3 (注解方式):
import lombok.extern.slf4j.Slf4j; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Service; /** * 新用户告知消息 * @author nieweijun * @since 2021/5/31 14:29 */ @Service @Slf4j public class RegisterNoticeService { @EventListener public void notice(RegisterEvent event) { log.info("#=====>[RegisterNoticeService.notice] 消息告知:{} 你好! 欢迎你加入社团, 您须要遵照如下规定 1, 2, 3, 4, 5 =====#", event.getUserName()); } }
3. 事件发布:
import lombok.extern.slf4j.Slf4j; import org.springframework.context.ApplicationEventPublisher; import org.springframework.context.ApplicationEventPublisherAware; import org.springframework.stereotype.Service; @Service @Slf4j public class UserBizService implements ApplicationEventPublisherAware { private ApplicationEventPublisher applicationEventPublisher; @Override public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) { this.applicationEventPublisher = applicationEventPublisher; } public void register(String userName){ // 1. 执行注册逻辑 log.info("#=====>用户 [{}] 注册逻辑成功!", userName); // 2. 发布事件 applicationEventPublisher.publishEvent(new RegisterEvent(this, userName)); } }
4. 测试用例:
import lombok.extern.slf4j.Slf4j; import org.junit.jupiter.api.Test; import org.springframework.boot.test.context.SpringBootTest; import javax.annotation.Resource; /** * 设计模式测试用例 * @author nieweijun * @since 2021/6/1 18:20 */ @Slf4j @SpringBootTest public class PatternObserverTest { @Resource private UserBizService userBizService; // 3. spring事件监听测试 @Test void testRegister() { //@SpringBootTest userBizService.register("niewj"); } }
5. 执行结果:
listener.UserBizService : #=====>用户 [niewj] 注册逻辑成功! listener.RegisterNoticeService : #=====>[RegisterNoticeService.notice] 消息告知:niewj 你好! 欢迎你加入社团, 您须要遵照如下规定 1, 2, 3, 4, 5 =====# listener.CouponServiceListener : #=====>[CouponService.onApplicationEvent] 给用户niewj发放3张满减新手券! =====# listener.EmailServiceListener : #=====>[EmailService.onApplicationEvent] 执行发邮件给用户: niewj =====#
btn.addActionListener
1. button单击事件绑定监听
import javax.swing.*; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; /** * java GUI 观察者(监听器) * @author nieweijun * @since 2021/6/1 22:21 */ public class GuiObserver { public GuiObserver() { JFrame jFrame = new JFrame("HelloButton"); // 1. button 事件源 JButton btn = new JButton("click me~"); // 2. 事件监听器(携带监听事件 ActionEvent) ActionListener myListener = new ActionListener() { @Override public void actionPerformed(ActionEvent e) { JOptionPane.showMessageDialog(null, "按钮被点击!"); } }; // 3. 注册事件 btn.addActionListener(myListener); // btn.addActionListener((e) -> JOptionPane.showMessageDialog(null, "按钮被点击!")); jFrame.add(btn); jFrame.setLayout(new FlowLayout()); jFrame.setSize(500,400); jFrame.setLocation(400, 400); jFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); jFrame.setVisible(true); } public static void main(String[] args) { new GuiObserver(); } }
执行结果:
EventBus#register#post
import com.google.common.eventbus.Subscribe; import lombok.extern.slf4j.Slf4j; /** * 事件监听器 * @author nieweijun * @since 2021/6/9 13:34 */ @Slf4j public class EventListener { @Subscribe public void listenString(String msg){ log.info("#======>EventListener.listenString:{}", msg); } @Subscribe public void listenInteger(Integer num){ log.info("@======>EventListener.listenInteger:{}", num); } }
调用测试:
// 4. Guava EventBus 简单测试用例 @Test void testEventBus() { EventBus eventBus = new EventBus(); // register eventBus.register(new EventListener()); // post eventBus.post("somename"); eventBus.post(10); }
输出结果:
eventBus.EventListener - #======>EventListener.listenString:somename eventBus.EventListener - @======>EventListener.listenInteger:10