EventBus是Guava的事件处理机制，是设计模式中的观察者模式（生产/消费者编程模型）的优雅实现。对于事件监听和发布订阅模式，EventBus是一个非常优雅和简单解决方案，我们不用创建复杂的类和接口层次结构。
定义EventBus
@Configuration
public class EventBusConfig {
@Autowired
private ApplicationContext context;
/**
* 功能描述: <br>
* ConditionalOnMissingBean判断是否执行初始化代码，即如果用户已经创建bean，则相关的初始化代码不再执行
*/
@Bean
@ConditionalOnMissingBean(AsyncEventBus.class)
AsyncEventBus createEventBus() {
// 定义一个EventBus对象
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("注册监听器：" + context.getBean(method.getDeclaringClass()));
eventBus.register(context.getBean(method.getDeclaringClass()));
} catch (Exception e) {
e.printStackTrace();
}
}
}
return eventBus;
}
}
定义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 ......");
}
}
定义Listener
public interface IEventListener {
void login(LoginEvent event);
void business(BusinessEvent event);
void logout(LogoutEvent event);
}
/**
* 同一个监听者可以监听多种类型的事件
*/
@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();
}
}
/**
* 同一个监听器多次监听同一个事件
*/
@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) {
}
}
定义事件发布接口
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) {
// 事件发布
eventBus.post(event);
}
}
}
启动触发事件
@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);
}
}
启动类
@SpringBootApplication(exclude={DataSourceAutoConfiguration.class})
public class EventBusApplication {
public static void main(String[] args) {
try {
SpringApplication.run(EventBusApplication.class, args);
} catch (Exception e) {
e.printStackTrace();
}
}
}