Spring事件監聽器之@EventListener原理分析

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("我發佈瞭事件！！！"));
        System.out.println(" publishOrderEvent ");
        return "發送事件瞭！";
    }
}

public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, Object source) {
        //獲取對象
		DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
		
        //org.springframework.context.event.internalEventListenerProcessor
        //@EventListener註解處理器
		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
        //內部管理的EventListenerFactory的bean名稱
		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;
	}

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;
		//獲取容器中所有的EventListenerFactory，並把他們實例化
		Map<String, EventListenerFactory> beans = beanFactory.getBeansOfType(EventListenerFactory.class, false, false);
		
		List<EventListenerFactory> factories = new ArrayList<>(beans.values());
		AnnotationAwareOrderComparator.sort(factories);
		//將EventListenerFactory儲存到緩存eventListenerFactories中，便於後來使用
		this.eventListenerFactories = factories;
	}
}

public class EventListenerMethodProcessor implements SmartInitializingSingleton, ApplicationContextAware, BeanFactoryPostProcessor {
    @Override
	public void afterSingletonsInstantiated() {
		ConfigurableListableBeanFactory beanFactory = this.beanFactory;
		Assert.state(this.beanFactory != null, "No ConfigurableListableBeanFactory set");
		// 這裡厲害瞭，用Object.class 是拿出容器裡面所有的Bean定義~~~  一個一個的檢查
		String[] beanNames = beanFactory.getBeanNamesForType(Object.class);
		for (String beanName : beanNames) {
		     // 
			if (!ScopedProxyUtils.isScopedTarget(beanName)) {
				Class<?> type = null;
				try {
				     // 防止是代理，吧真實的類型拿出來
					type = AutoProxyUtils.determineTargetClass(beanFactory, beanName);
				}
				catch (Throwable ex) {
					if (logger.isDebugEnabled()) {
						logger.debug("", ex);
					}
				}
				if (type != null) {
				    // 對專門的作用域對象進行兼容~~~~（絕大部分都用不著）
					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 {
					    // 真正處理這個Bean裡面的方法們。。。
						processBean(beanName, type);
					}
					catch (Throwable ex) {
						throw new BeanInitializationException("", ex);
					}
				}
			}
		}
	}
	private void processBean(final String beanName, final Class<?> targetType) {
	         //類上有@Component註解
			if (!this.nonAnnotatedClasses.contains(targetType) &&!targetType.getName().startsWith("java") &&!isSpringContainerClass(targetType)) {
	 			Map<Method, EventListener> annotatedMethods = null;
				try {
				    //獲取類中用@EventListener標註方法的信息
					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為空，那代表類中沒有用@EventListener標註的方法
				if (CollectionUtils.isEmpty(annotatedMethods)) {
					this.nonAnnotatedClasses.add(targetType);
					if (logger.isTraceEnabled()) {
						logger.trace("" + targetType.getName());
					}
				}
				else {
					// 類中存在用@EventListener標註的方法
					ConfigurableApplicationContext context = this.applicationContext;
					Assert.state(context != null, "No ApplicationContext set");
					//獲取容器中所有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)) {
								// 簡單的說，就是把這個方法弄成一個可以執行的方法（主要和訪問權限有關）
							  // 這裡註意：若你是JDK的代理類，請不要在實現類裡書寫@EventListener註解的監聽器，否則會報錯的。（CGLIB代理的木關系） 
								Method methodToUse = AopUtils.selectInvocableMethod(method, context.getType(beanName)); 
                                //利用EventListenerFactory創建ApplicationListener，詳情後面說
								ApplicationListener<?> applicationListener =
										factory.createApplicationListener(beanName, targetType, methodToUse);
								//如果ApplicationListener是ApplicationListenerMethodAdapter類，那麼執行其init方法
								if (applicationListener instanceof ApplicationListenerMethodAdapter) {
									((ApplicationListenerMethodAdapter) applicationListener).init(context, this.evaluator);
								}
								//放到容器中
								context.addApplicationListener(applicationListener);
								//@EventListener方法隻能解析一次
								break;
							}
						}
					}
					if (logger.isDebugEnabled()) {
						logger.debug();
					}
				}
			}
		}
}	

public interface EventListenerFactory {
    //是否支持當前方法
	boolean supportsMethod(Method method);
	
	//生成一個ApplicationListener
	ApplicationListener<?> createApplicationListener(String beanName, Class<?> type, Method method);
}

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);
	}
}

public class ApplicationListenerMethodAdapter implements GenericApplicationListener {
	private final String beanName; //@EventListener方法所屬bean的名字
	private final Method method;//@EventListener標註的方法
	private final Method targetMethod;//@EventListener標註的真實方法對象，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;//存儲方法的參數
	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);
		//獲取方法上的@EventListener註解對象
		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);
		//根據@EventListener的condition，判斷是否要處理
		if (shouldHandle(event, args)) {
		    //調用方法
			Object result = doInvoke(args);
			if (result != null) {
			    //如果有監聽器可以監聽這個結果，那麼可以觸發那個監聽器
				handleResult(result);
			}
			else {
				logger.trace("No result object given - no result to handle");
			}
		}
	}
}

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解析耗時
    }
//自動補全剩餘實現方法
}

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 {
                
            }
        });
    //自動補全剩餘實現方法
public class HttpEventListener extends EventListener {
    /**
     * 每次請求的標識
     */
    private long callId = 1L;
    /**
     * 每次請求的開始時間，單位納秒
     */
    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解析耗時
        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);
    }
}
//利用反射將logHandler打回來的數據存到對象
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;
    }