EventBus是Guava的事件處理機制，是設計模式中的觀察者模式（生產/消費者編程模型）的優雅實現。對於事件監聽和發佈訂閱模式，EventBus是一個非常優雅和簡單解決方案，我們不用創建複雜的類和接口層次結構。
定義EventBus
@Configuration
public class EventBusConfig {
@Autowired
private ApplicationContext context;
/**
* 功能描述: <br>
* ConditionalOnMissingBean判斷是否執行初始化代碼，即如果用戶已經創建bean，則相關的初始化代碼不再執行
*/
@Bean
@ConditionalOnMissingBean(AsyncEventBus.class)
AsyncEventBus createEventBus() {
// 定義一個EventBus對象
AsyncEventBus eventBus = new AsyncEventBus(Executors.newFixedThreadPool(5));
Reflections reflections = new Reflections("com.google.guava.listener", new MethodAnnotationsScanner());
Set<Method> methods = reflections.getMethodsAnnotatedWith(Subscribe.class);
if (null != methods) {
for (Method method : methods) {
try {
System.out.println("註冊監聽器：" + context.getBean(method.getDeclaringClass()));
eventBus.register(context.getBean(method.getDeclaringClass()));
} catch (Exception e) {
e.printStackTrace();
}
}
}
return eventBus;
}
}
定義Event
public interface IEvent {
void print();
}
public class LoginEvent implements IEvent{
@Override
public void print() {
System.out.println("login ......");
}
}
public class LogoutEvent implements IEvent {
@Override
public void print() {
System.out.println("logout ......");
}
}
public class BusinessEvent implements IEvent{
@Override
public void print() {
System.out.println("business ......");
}
}
定義Listener
public interface IEventListener {
void login(LoginEvent event);
void business(BusinessEvent event);
void logout(LogoutEvent event);
}
/**
* 同一個監聽者可以監聽多種類型的事件
*/
@Component
public class LoginEventListener extends EventListenerAdapter {
@Subscribe
@Override
public void login(LoginEvent event) {
System.out.println("login receive event ...");
event.print();
}
@Subscribe
@Override
public void business(BusinessEvent event) {
System.out.println("business receive event ...");
event.print();
}
}
/**
* 同一個監聽器多次監聽同一個事件
*/
@Component
public class LogoutEventListener extends EventListenerAdapter{
@Subscribe
@Override
public void logout(LogoutEvent event) {
System.out.println("logout receive event ...");
event.print();
}
@Subscribe
public void logoutT(LogoutEvent event) {
System.out.println("logoutT receive event ...");
event.print();
}
}
public abstract class EventListenerAdapter implements IEventListener{
@Override
public void login(LoginEvent event) {
}
@Override
public void business(BusinessEvent enent) {
}
@Override
public void logout(LogoutEvent event) {
}
}
定義事件發佈接口
public interface IBusinessService {
void post(IEvent event);
}
@Service
public class BusinessServiceImpl implements IBusinessService {
@Autowired
private AsyncEventBus eventBus;
@Override
public void post(IEvent event) {
if (null != event) {
// 事件發佈
eventBus.post(event);
}
}
}
啓動觸發事件
@Component
public class StartRunner implements CommandLineRunner {
@Autowired
private IBusinessService businessService;
@Override
public void run(String... args) throws Exception {
IEvent loginEvent = new LoginEvent();
businessService.post(loginEvent);
IEvent logoutEvent = new LogoutEvent();
businessService.post(logoutEvent);
IEvent businessEvent = new BusinessEvent();
businessService.post(businessEvent);
}
}
啓動類
@SpringBootApplication(exclude={DataSourceAutoConfiguration.class})
public class EventBusApplication {
public static void main(String[] args) {
try {
SpringApplication.run(EventBusApplication.class, args);
} catch (Exception e) {
e.printStackTrace();
}
}
}