Spring事件监听器之@EventListener原理分析
作者:这是一条海鱼
Spring事件监听器之@EventListener原理
Spring为我们提供的一个事件监听、订阅的实现,内部实现原理是观察者设计模式;为的就是业务系统逻辑的解耦,提高可扩展性以及可维护性。事件发布者并不需要考虑谁去监听,监听具体的实现内容是什么,发布者的工作只是为了发布事件而已。
在spring中我们可以通过实现ApplicationListener接口或者@EventListener接口来实现事件驱动编程
比如我们做一个电商系统,用户下单支付成功后,我们一般要发短信或者邮箱给用户提示什么的,这时候就可以把这个通知业务做成一个单独事件监听,等待通知就可以了;把它解耦处理。
public class OrderEvent extends ApplicationEvent { public OrderEvent(Object source) { super(source); } } @Component public class OrderEventListener { @EventListener public void listener(OrderEvent event) { System.out.println("i do OrderEventListener" ); } } @Controller @RequestMapping("person") public class PersonController implements ApplicationContextAware { private ApplicationContext applicationContext; @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; } @ResponseBody @GetMapping("publishOrderEvent") public String publishOrderEvent() { applicationContext.publishEvent(new OrderEvent("我发布了事件!!!")); System.out.println(" publishOrderEvent "); return "发送事件了!"; } }
EventListenerMethodProcessor是@EventListener的解析类,他是一个SmartInitializingSingleton和BeanFactoryPostProcessor
一、解析@EventListener前的准备工作
1.1 EventListenerFactory和EventListenerMethodProcessor的注入
EventListenerFactory是把@EventListener标注的方法变成ApplicationListener的关键,其是在容器最初期(refresh方法发生前)就放到容器中去
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, Object source) { //获取对象 DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); //org.springframework.context.event.internalEventListenerProcessor //@EventListener注解处理器 if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME)); } //org.springframework.context.event.internalEventListenerProcessor //内部管理的EventListenerFactory的bean名称 if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class); def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME)); } return beanDefs; }
- 如果容器中没有名字是org.springframework.context.event.internalEventListenerProcessor的bean,那么就注入一个EventListenerMethodProcessor到容器中
- 如果容器中没有名字是org.springframework.context.event.internalEventListenerProcessor的bean,那么就注入一个DefaultEventListenerFactory到容器中
1.2 EventListenerMethodProcessor和EventListenerFactory关系的建立
EventListenerMethodProcessor会在容器启动时被注入到容器中,他是一个BeanFactoryPostProcessor,EventListenerMethodProcessor和EventListenerFactory关系的建立就发生在其方法postProcessBeanFactory中
public class EventListenerMethodProcessor implements SmartInitializingSingleton, ApplicationContextAware, BeanFactoryPostProcessor { @Nullable private List<EventListenerFactory> eventListenerFactories; //初始化eventListenerFactories @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) { this.beanFactory = beanFactory; //获取容器中所有的EventListenerFactory,并把他们实例化 Map<String, EventListenerFactory> beans = beanFactory.getBeansOfType(EventListenerFactory.class, false, false); List<EventListenerFactory> factories = new ArrayList<>(beans.values()); AnnotationAwareOrderComparator.sort(factories); //将EventListenerFactory储存到缓存eventListenerFactories中,便于后来使用 this.eventListenerFactories = factories; } }
EventListenerFactory的实例化时机只比BeanFactoryPostProcessor完点,他比BeanPostProcessor实例化时机早
二、开始解析@EventListener
EventListenerMethodProcessor是一个SmartInitializingSingleton,所以他会在所以bean实例化后,执行其afterSingletonsInstantiated方法
注意:只有单例的SmartInitializingSingleton,才会执行其afterSingletonsInstantiated方法
2.1 基本流程
public class EventListenerMethodProcessor implements SmartInitializingSingleton, ApplicationContextAware, BeanFactoryPostProcessor { @Override public void afterSingletonsInstantiated() { ConfigurableListableBeanFactory beanFactory = this.beanFactory; Assert.state(this.beanFactory != null, "No ConfigurableListableBeanFactory set"); // 这里厉害了,用Object.class 是拿出容器里面所有的Bean定义~~~ 一个一个的检查 String[] beanNames = beanFactory.getBeanNamesForType(Object.class); for (String beanName : beanNames) { // if (!ScopedProxyUtils.isScopedTarget(beanName)) { Class<?> type = null; try { // 防止是代理,吧真实的类型拿出来 type = AutoProxyUtils.determineTargetClass(beanFactory, beanName); } catch (Throwable ex) { if (logger.isDebugEnabled()) { logger.debug("", ex); } } if (type != null) { // 对专门的作用域对象进行兼容~~~~(绝大部分都用不着) if (ScopedObject.class.isAssignableFrom(type)) { try { Class<?> targetClass = AutoProxyUtils.determineTargetClass( beanFactory, ScopedProxyUtils.getTargetBeanName(beanName)); if (targetClass != null) { type = targetClass; } } catch (Throwable ex) { // An invalid scoped proxy arrangement - let's ignore it. if (logger.isDebugEnabled()) { logger.debug("Could not resolve target bean for scoped proxy '" + beanName + "'", ex); } } } try { // 真正处理这个Bean里面的方法们。。。 processBean(beanName, type); } catch (Throwable ex) { throw new BeanInitializationException("", ex); } } } } } private void processBean(final String beanName, final Class<?> targetType) { //类上有@Component注解 if (!this.nonAnnotatedClasses.contains(targetType) &&!targetType.getName().startsWith("java") &&!isSpringContainerClass(targetType)) { Map<Method, EventListener> annotatedMethods = null; try { //获取类中用@EventListener标注方法的信息 annotatedMethods = MethodIntrospector.selectMethods(targetType, (MethodIntrospector.MetadataLookup<EventListener>) method -> AnnotatedElementUtils.findMergedAnnotation(method, EventListener.class)); } catch (Throwable ex) { // An unresolvable type in a method signature, probably from a lazy bean - let's ignore it. if (logger.isDebugEnabled()) { logger.debug("Could not resolve methods for bean with name '" + beanName + "'", ex); } } //如果annotatedMethods为空,那代表类中没有用@EventListener标注的方法 if (CollectionUtils.isEmpty(annotatedMethods)) { this.nonAnnotatedClasses.add(targetType); if (logger.isTraceEnabled()) { logger.trace("" + targetType.getName()); } } else { // 类中存在用@EventListener标注的方法 ConfigurableApplicationContext context = this.applicationContext; Assert.state(context != null, "No ApplicationContext set"); //获取容器中所有EventListenerFactory List<EventListenerFactory> factories = this.eventListenerFactories; Assert.state(factories != null, "EventListenerFactory List not initialized"); for (Method method : annotatedMethods.keySet()) { for (EventListenerFactory factory : factories) { if (factory.supportsMethod(method)) { // 简单的说,就是把这个方法弄成一个可以执行的方法(主要和访问权限有关) // 这里注意:若你是JDK的代理类,请不要在实现类里书写@EventListener注解的监听器,否则会报错的。(CGLIB代理的木关系) Method methodToUse = AopUtils.selectInvocableMethod(method, context.getType(beanName)); //利用EventListenerFactory创建ApplicationListener,详情后面说 ApplicationListener<?> applicationListener = factory.createApplicationListener(beanName, targetType, methodToUse); //如果ApplicationListener是ApplicationListenerMethodAdapter类,那么执行其init方法 if (applicationListener instanceof ApplicationListenerMethodAdapter) { ((ApplicationListenerMethodAdapter) applicationListener).init(context, this.evaluator); } //放到容器中 context.addApplicationListener(applicationListener); //@EventListener方法只能解析一次 break; } } } if (logger.isDebugEnabled()) { logger.debug(); } } } } }
获取容器中所有的类,把用@Component标注的类上所有的@EventListener方法用EventListenerFactory解析成一个ApplicationListener
@EventListener方法只要有到一个可以解析他的EventListenerFactory,就不会让其他EventListenerFactory解析他了 所以如果容器中存在多个EventListenerFactory,我要注意他的顺序
2.2 EventListenerFactory解析@EventListener
public interface EventListenerFactory { //是否支持当前方法 boolean supportsMethod(Method method); //生成一个ApplicationListener ApplicationListener<?> createApplicationListener(String beanName, Class<?> type, Method method); }
EventListenerFactory有2个字类DefaultEventListenerFactory和TransactionalEventListenerFactory,DefaultEventListenerFactory是处理@EventListener,而TransactionalEventListenerFactory是处理@TransactionalEventListener的,Spring默认就有DefaultEventListenerFactory,而TransactionalEventListenerFactory是没有的,所以我们想要支持@TransactionalEventListener,就要注册一个TransactionalEventListenerFactory,也就是要说要使用@EnableTransactionManagement注解
public class DefaultEventListenerFactory implements EventListenerFactory, Ordered { private int order = LOWEST_PRECEDENCE; @Override public boolean supportsMethod(Method method) { return true; } @Override public ApplicationListener<?> createApplicationListener(String beanName, Class<?> type, Method method) { return new ApplicationListenerMethodAdapter(beanName, type, method); } }
ApplicationListenerMethodAdapter一个ApplicationListener,他是用来包装@EventListener标注的方法
public class ApplicationListenerMethodAdapter implements GenericApplicationListener { private final String beanName; //@EventListener方法所属bean的名字 private final Method method;//@EventListener标注的方法 private final Method targetMethod;//@EventListener标注的真实方法对象,防止其是代理方法 //方法申明,如public void demo.Ball.applicationContextEvent(demo.OrderEvent) private final AnnotatedElementKey methodKey; private final List<ResolvableType> declaredEventTypes;//存储方法的参数 private final String condition;//@EventListener的condition private final int order; private ApplicationContext applicationContext; private EventExpressionEvaluator evaluator;//@EventListener的EventExpressionEvaluator public ApplicationListenerMethodAdapter(String beanName, Class<?> targetClass, Method method) { this.beanName = beanName; this.method = BridgeMethodResolver.findBridgedMethod(method); this.targetMethod = (!Proxy.isProxyClass(targetClass) ?AopUtils.getMostSpecificMethod(method, targetClass) : this.method); this.methodKey = new AnnotatedElementKey(this.targetMethod, targetClass); //获取方法上的@EventListener注解对象 EventListener ann = AnnotatedElementUtils.findMergedAnnotation(this.targetMethod, EventListener.class); this.declaredEventTypes = resolveDeclaredEventTypes(method, ann); this.condition = (ann != null ? ann.condition() : null); this.order = resolveOrder(this.targetMethod); } public void onApplicationEvent(ApplicationEvent event) { processEvent(event); } public void processEvent(ApplicationEvent event) { Object[] args = resolveArguments(event); //根据@EventListener的condition,判断是否要处理 if (shouldHandle(event, args)) { //调用方法 Object result = doInvoke(args); if (result != null) { //如果有监听器可以监听这个结果,那么可以触发那个监听器 handleResult(result); } else { logger.trace("No result object given - no result to handle"); } } } }
EventListener.Factory
EventListener.Factory监听网络请求全过程
网上介绍的并不多,关于它的使用方式,可能会存在很多坑。
主要是为了监听网络请求过程。
首先OkHttpClient.Builder.eventListenerFactory需要的是一个实现了EventListener接口的工厂类。
简单的实现方式。
public class HttpEventListener extends EventListener { private final long callId; final AtomicLong nextCallId = new AtomicLong(1L); @Override public EventListener create(Call call) { long callId = nextCallId.getAndIncrement(); return new HttpEventListener(callId, System.nanoTime()); } public HttpEventListener(long callId, long callStartNanos) { this.callId = callId; this.callStartNanos = callStartNanos; } private long dnsStartTime; private long dnsParseTime; @Override public void dnsStart(Call call, String domainName) { super.dnsStart(call, domainName); dnsStartTime = System.nanoTime(); } @Override public void dnsEnd(Call call, String domainName, List<InetAddress> inetAddressList) { super.dnsEnd(call, domainName, inetAddressList); dnsParseTime = System.nanoTime() - dnsStartTime;//dns解析耗时 } //自动补全剩余实现方法 }
EventListener.create方法在okHttpClient.newCall后执行
dnsParseTime可以算出dns解析耗时,还可以监听每次dns解析的domain,解析的结果inetAddressList。
这个是比较好用的。
问题是如何将这些数据回传回来呢
在OkHttpClient构造时传入自定义参数
OkHttpClient.Builder builder = new OkHttpClient.Builder(); final ResponseTag tag = new ResponseTag(); tag.logHandler = logHandler; httpClient.newCall(requestBuilder.tag(tag).build()).enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { } @Override public void onResponse(Call call, Response response) throws IOException { } }); //自动补全剩余实现方法 public class HttpEventListener extends EventListener { /** * 每次请求的标识 */ private long callId = 1L; /** * 每次请求的开始时间,单位纳秒 */ private final long callStartNanos; private long total_elapsed_time; private long dns_elapsed_time; private long connect_elapsed_time; private long tls_connect_elapsed_time; private long request_elapsed_time; private long wait_elapsed_time; private long response_elapsed_time; private Client.ResponseTag responseTag; private LogHandler logHandler; private long start_dns_elapsed_time; private long start_total_elapsed_time; private long start_connect_elapsed_time; private long start_tls_connect_elapsed_time; private long start_request_elapsed_time; private long start_response_elapsed_time; public HttpEventListener(long callId, Client.ResponseTag responseTag, long callStartNanos) { this.callId = callId; this.callStartNanos = callStartNanos; this.responseTag = responseTag; this.logHandler = responseTag.logHandler; } public static final Factory FACTORY = new Factory() { final AtomicLong nextCallId = new AtomicLong(1L); @Override public EventListener create(@NotNull Call call) { long callId = nextCallId.getAndIncrement(); return new HttpEventListener(callId, (Client.ResponseTag) call.request().tag(), System.nanoTime()); } }; @Override public void callStart(Call call) { super.callStart(call); start_total_elapsed_time = System.currentTimeMillis(); } @Override public void dnsStart(Call call, String domainName) { super.dnsStart(call, domainName); start_dns_elapsed_time = System.currentTimeMillis(); } @Override public void dnsEnd(Call call, String domainName, List<InetAddress> inetAddressList) { super.dnsEnd(call, domainName, inetAddressList); dns_elapsed_time = System.currentTimeMillis() - start_dns_elapsed_time;//dns解析耗时 logHandler.send("dns_elapsed_time", dns_elapsed_time); } @Override public void connectStart(Call call, InetSocketAddress inetSocketAddress, Proxy proxy) { super.connectStart(call, inetSocketAddress, proxy); start_connect_elapsed_time = System.currentTimeMillis(); } @Override public void secureConnectStart(Call call) { super.secureConnectStart(call); start_tls_connect_elapsed_time = System.currentTimeMillis(); } @Override public void secureConnectEnd(Call call, Handshake handshake) { super.secureConnectEnd(call, handshake); tls_connect_elapsed_time = System.currentTimeMillis() - start_tls_connect_elapsed_time; logHandler.send("tls_connect_elapsed_time", tls_connect_elapsed_time); } @Override public void connectEnd(Call call, InetSocketAddress inetSocketAddress, Proxy proxy, Protocol protocol) { super.connectEnd(call, inetSocketAddress, proxy, protocol); connect_elapsed_time = System.currentTimeMillis() - start_connect_elapsed_time; logHandler.send("connect_elapsed_time", connect_elapsed_time); } @Override public void connectFailed(Call call, InetSocketAddress inetSocketAddress, Proxy proxy, Protocol protocol, IOException ioe) { super.connectFailed(call, inetSocketAddress, proxy, protocol, ioe); } @Override public void connectionAcquired(Call call, Connection connection) { super.connectionAcquired(call, connection); } @Override public void connectionReleased(Call call, Connection connection) { super.connectionReleased(call, connection); } @Override public void requestHeadersStart(Call call) { super.requestHeadersStart(call); start_request_elapsed_time = System.currentTimeMillis(); } @Override public void requestHeadersEnd(Call call, Request request) { super.requestHeadersEnd(call, request); } @Override public void requestBodyStart(Call call) { super.requestBodyStart(call); } @Override public void requestBodyEnd(Call call, long byteCount) { super.requestBodyEnd(call, byteCount); request_elapsed_time = System.currentTimeMillis() - start_request_elapsed_time; logHandler.send("request_elapsed_time", request_elapsed_time); } @Override public void responseHeadersStart(Call call) { super.responseHeadersStart(call); start_response_elapsed_time = System.currentTimeMillis(); } @Override public void responseHeadersEnd(Call call, Response response) { super.responseHeadersEnd(call, response); } @Override public void responseBodyStart(Call call) { super.responseBodyStart(call); } @Override public void responseBodyEnd(Call call, long byteCount) { super.responseBodyEnd(call, byteCount); response_elapsed_time = System.currentTimeMillis() - start_response_elapsed_time; wait_elapsed_time = System.currentTimeMillis() - start_request_elapsed_time; logHandler.send("response_elapsed_time", response_elapsed_time); logHandler.send("wait_elapsed_time", wait_elapsed_time); } @Override public void callEnd(Call call) { super.callEnd(call); total_elapsed_time = System.currentTimeMillis() - start_total_elapsed_time; logHandler.send("total_elapsed_time", total_elapsed_time); } @Override public void callFailed(Call call, IOException ioe) { super.callFailed(call, ioe); } } //利用反射将logHandler打回来的数据存到对象 public static LogHandler getUplogHandler(final Object obj) { final String setMethod = "set"; LogHandler logHandler = new LogHandler() { @Override public void send(String key, Object value) { try { if (value instanceof String) { Method setByKey = obj.getClass().getMethod(setMethod + StringUtils.upperCase(key), Class.forName("java.lang.String")); setByKey.invoke(obj, value); } else if (value instanceof Integer) { Method setByKey = obj.getClass().getMethod(setMethod + StringUtils.upperCase(key), int.class); setByKey.invoke(obj, value); } else if (value instanceof Long) { Method setByKey = obj.getClass().getMethod(setMethod + StringUtils.upperCase(key), long.class); setByKey.invoke(obj, value); } } catch (NoSuchMethodException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } @Override public Object getUploadInfo() { return obj; } }; return logHandler; }
以上为个人经验,希望能给大家一个参考,也希望大家多多支持脚本之家。