目录Spring事件监听器之@EventListener原理一、解析@EventListener前的准备工作二、开始解析@EventListenerEventListener.FactoryEventListener.Factory监听网络请求全过程问题是如何将这些数据回传回来呢
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); }}@Componentpublic 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 {@Nullableprivate List<EventListenerFactory> eventListenerFactories; //初始化eventListenerFactories@Overridepublic 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 { @Overridepublic 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EventListenerFactoryList<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ApplicationListenerApplicationListener<?> 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;@Overridepublic boolean supportsMethod(Method method) {return true;}@Overridepublic 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conditionprivate final int order;private ApplicationContext applicationContext;private EventExpressionEvaluator evaluator;//@EventListener的EventExpressionEvaluatorpublic 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。
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