spring学习总结005 --- IOC容器启动源码（事件机制）

protected void initApplicationEventMulticaster() {
    // 获取BeanFactory, 默认是DefaultListableBeanFactory
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 如果用户定义了name为applicationEventMulticaster的事件广播器, 直接将其作为容器的事件广播器
    if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
        this.applicationEventMulticaster =
                beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
        if (logger.isTraceEnabled()) {
            logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
        }
    }
    else {
        // 未自定义bean, 使用SimpleApplicationEventMulticaster
        this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
        // 将默认事件广播器存放到BeanFactory的beanDefinationMap中
        beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
        if (logger.isTraceEnabled()) {
            logger.trace("No ‘" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "‘ bean, using " +
                    "[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
        }
    }
}

public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
    // 获取事件类型
    ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
    // 获取线程池
    Executor executor = getTaskExecutor();
    // 通过事件及类型获取对应的事件监听器
    for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {
        // 异步或者同步方式广播事件
        if (executor != null) {
            executor.execute(() -> invokeListener(listener, event));
        }
        else {
            invokeListener(listener, event);
        }
    }
}

protected void invokeListener(ApplicationListener<?> listener, ApplicationEvent event) {
    ErrorHandler errorHandler = getErrorHandler();
    if (errorHandler != null) {
        try {
            doInvokeListener(listener, event);
        }
        catch (Throwable err) {
            errorHandler.handleError(err);
        }
    }
    else {
        doInvokeListener(listener, event);
    }
}

private void doInvokeListener(ApplicationListener listener, ApplicationEvent event) {
    try {
        // listener处理
        listener.onApplicationEvent(event);
    }
    catch (ClassCastException ex) {
        String msg = ex.getMessage();
        if (msg == null || matchesClassCastMessage(msg, event.getClass())) {
            Log logger = LogFactory.getLog(getClass());
            if (logger.isTraceEnabled()) {
                logger.trace("Non-matching event type for listener: " + listener, ex);
            }
        }
        else {
            throw ex;
        }
    }
}

public class UserApplicationEvent extends ApplicationEvent {

    public UserApplicationEvent(User user) {
        super(user);
    }
}

@Slf4j
@Component
public class UserApplicationEventPublisher implements ApplicationEventPublisherAware {

    private ApplicationEventPublisher applicationEventPublisher;

    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.applicationEventPublisher = applicationEventPublisher;
    }

    public void saveUser(User user) {
        log.info("start publish event.....");
        applicationEventPublisher.publishEvent(new UserApplicationEvent(user));
    }
}

@Slf4j
@Component
public class UserEventListener implements ApplicationListener<UserApplicationEvent> {
    @Override
    public void onApplicationEvent(UserApplicationEvent event) {
        log.info("Recv event:{}", event.getSource());
    }
}

public class Test11 {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:bean10.xml");
        UserApplicationEventPublisher publisher = context.getBean(UserApplicationEventPublisher.class);
        publisher.saveUser(User.builder()
                .id(1)
                .name("bale")
                .info(Info.builder().age(28).build())
                .build());
    }
}