spring 5.1.2 mvc RequestMappingHandlerMapping 源码初始化过程

RequestMappingHandlerMapping getMappingForMethod

RequestMappingHandlerMapping 继承于 AbstractHandlerMethodMapping 而AbstractHandlerMethodMapping实现了InitializingBean接口，

会调用初始化后的方法afterPropertiesSet（），此方法中主要功能是通过isHandler(beanType)把类及方法中包括Controller RequestMapping注解的所有的类都找出来，

然后循环每个类，找出所有方法相对应的url路径（结合class RequestMapping注解的路径）组合成完整的请求路径，然后注册到MappingRegistry 类的集合中，以便后面使用

	/**
	 * {@inheritDoc}
	 * <p>Expects a handler to have either a type-level @{@link Controller}
	 * annotation or a type-level @{@link RequestMapping} annotation.
	 */
	@Override
	protected boolean isHandler(Class<?> beanType) {
		return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
				AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
	}

	/**
	 * Uses method and type-level @{@link RequestMapping} annotations to create
	 * the RequestMappingInfo.
	 * @return the created RequestMappingInfo, or {@code null} if the method
	 * does not have a {@code @RequestMapping} annotation.
	 * @see #getCustomMethodCondition(Method)
	 * @see #getCustomTypeCondition(Class)
	 */
	@Override
	@Nullable
	protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
		RequestMappingInfo info = createRequestMappingInfo(method);
		if (info != null) {
			RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
			if (typeInfo != null) {
				info = typeInfo.combine(info);
			}
			String prefix = getPathPrefix(handlerType);
			if (prefix != null) {
				info = RequestMappingInfo.paths(prefix).build().combine(info);
			}
		}
		return info;
	}

	@Nullable
	String getPathPrefix(Class<?> handlerType) {
		for (Map.Entry<String, Predicate<Class<?>>> entry : this.pathPrefixes.entrySet()) {
			if (entry.getValue().test(handlerType)) {
				String prefix = entry.getKey();
				if (this.embeddedValueResolver != null) {
					prefix = this.embeddedValueResolver.resolveStringValue(prefix);
				}
				return prefix;
			}
		}
		return null;
	}

	/**
	 * Delegates to {@link #createRequestMappingInfo(RequestMapping, RequestCondition)},
	 * supplying the appropriate custom {@link RequestCondition} depending on whether
	 * the supplied {@code annotatedElement} is a class or method.
	 * @see #getCustomTypeCondition(Class)
	 * @see #getCustomMethodCondition(Method)
	 */
	@Nullable
	private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
		RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
		RequestCondition<?> condition = (element instanceof Class ?
				getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
		return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
	}

	/**
	 * Create a {@link RequestMappingInfo} from the supplied
	 * {@link RequestMapping @RequestMapping} annotation, which is either
	 * a directly declared annotation, a meta-annotation, or the synthesized
	 * result of merging annotation attributes within an annotation hierarchy.
	 */
	protected RequestMappingInfo createRequestMappingInfo(
			RequestMapping requestMapping, @Nullable RequestCondition<?> customCondition) {

		RequestMappingInfo.Builder builder = RequestMappingInfo
				.paths(resolveEmbeddedValuesInPatterns(requestMapping.path()))
				.methods(requestMapping.method())
				.params(requestMapping.params())
				.headers(requestMapping.headers())
				.consumes(requestMapping.consumes())
				.produces(requestMapping.produces())
				.mappingName(requestMapping.name());
		if (customCondition != null) {
			builder.customCondition(customCondition);
		}
		return builder.options(this.config).build();
	}

AbstractHandlerMethodMapping implements InitializingBean

	/**
	 * Provide the mapping for a handler method. A method for which no
	 * mapping can be provided is not a handler method.
	 * @param method the method to provide a mapping for
	 * @param handlerType the handler type, possibly a sub-type of the method's
	 * declaring class
	 * @return the mapping, or {@code null} if the method is not mapped
	 */
	@Nullable
	protected abstract T getMappingForMethod(Method method, Class<?> handlerType);

	/**
	 * Detects handler methods at initialization.
	 * @see #initHandlerMethods
	 */
	@Override
	public void afterPropertiesSet() {
		initHandlerMethods();
	}

	/**
	 * Scan beans in the ApplicationContext, detect and register handler methods.
	 * @see #getCandidateBeanNames()
	 * @see #processCandidateBean
	 * @see #handlerMethodsInitialized
	 */
	protected void initHandlerMethods() {
		for (String beanName : getCandidateBeanNames()) {
			if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
				processCandidateBean(beanName);
			}
		}
		handlerMethodsInitialized(getHandlerMethods());
	}

	/**
	 * Invoked after all handler methods have been detected.
	 * @param handlerMethods a read-only map with handler methods and mappings.
	 */
	protected void handlerMethodsInitialized(Map<T, HandlerMethod> handlerMethods) {
		// Total includes detected mappings + explicit registrations via registerMapping
		int total = handlerMethods.size();
		if ((logger.isTraceEnabled() && total == 0) || (logger.isDebugEnabled() && total > 0) ) {
			logger.debug(total + " mappings in " + formatMappingName());
		}
	}

	/**
	 * Determine the type of the specified candidate bean and call
	 * {@link #detectHandlerMethods} if identified as a handler type.
	 * <p>This implementation avoids bean creation through checking
	 * {@link org.springframework.beans.factory.BeanFactory#getType}
	 * and calling {@link #detectHandlerMethods} with the bean name.
	 * @param beanName the name of the candidate bean
	 * @since 5.1
	 * @see #isHandler
	 * @see #detectHandlerMethods
	 */
	protected void processCandidateBean(String beanName) {
		Class<?> beanType = null;
		try {
			beanType = obtainApplicationContext().getType(beanName);
		}
		catch (Throwable ex) {
			// An unresolvable bean type, probably from a lazy bean - let's ignore it.
			if (logger.isTraceEnabled()) {
				logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
			}
		}
		if (beanType != null && isHandler(beanType)) {
		//====================================
			detectHandlerMethods(beanName);
		}
	}

	/**
	 * Look for handler methods in the specified handler bean.
	 * @param handler either a bean name or an actual handler instance
	 * @see #getMappingForMethod
	 */
	protected void detectHandlerMethods(Object handler) {
		Class<?> handlerType = (handler instanceof String ?
				obtainApplicationContext().getType((String) handler) : handler.getClass());

		if (handlerType != null) {
			Class<?> userType = ClassUtils.getUserClass(handlerType);
			Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
					(MethodIntrospector.MetadataLookup<T>) method -> {
						try {
							return getMappingForMethod(method, userType);
						}
						catch (Throwable ex) {
							throw new IllegalStateException("Invalid mapping on handler class [" +
									userType.getName() + "]: " + method, ex);
						}
					});
			if (logger.isTraceEnabled()) {
				logger.trace("Mapped " + methods.size() + " handler method(s) for " + userType + ": " + methods);
			}
			methods.forEach((method, mapping) -> {
				Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
				registerHandlerMethod(handler, invocableMethod, mapping);
			});
		}
	}

	/**
	 * Register a handler method and its unique mapping. Invoked at startup for
	 * each detected handler method.
	 * @param handler the bean name of the handler or the handler instance
	 * @param method the method to register
	 * @param mapping the mapping conditions associated with the handler method
	 * @throws IllegalStateException if another method was already registered
	 * under the same mapping
	 */
	protected void registerHandlerMethod(Object handler, Method method, T mapping) {
		this.mappingRegistry.register(mapping, handler, method);
	}

	/**
	 * A registry that maintains all mappings to handler methods, exposing methods
	 * to perform lookups and providing concurrent access.
	 * <p>Package-private for testing purposes.
	 */
	class MappingRegistry {

		private final Map<T, MappingRegistration<T>> registry = new HashMap<>();

		private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<>();

		private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<>();

		private final Map<String, List<HandlerMethod>> nameLookup = new ConcurrentHashMap<>();

		private final Map<HandlerMethod, CorsConfiguration> corsLookup = new ConcurrentHashMap<>();

		private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();

		/**
		 * Return all mappings and handler methods. Not thread-safe.
		 * @see #acquireReadLock()
		 */
		public Map<T, HandlerMethod> getMappings() {
			return this.mappingLookup;
		}

		/**
		 * Return matches for the given URL path. Not thread-safe.
		 * @see #acquireReadLock()
		 */
		@Nullable
		public List<T> getMappingsByUrl(String urlPath) {
			return this.urlLookup.get(urlPath);
		}

		/**
		 * Return handler methods by mapping name. Thread-safe for concurrent use.
		 */
		public List<HandlerMethod> getHandlerMethodsByMappingName(String mappingName) {
			return this.nameLookup.get(mappingName);
		}

		/**
		 * Return CORS configuration. Thread-safe for concurrent use.
		 */
		public CorsConfiguration getCorsConfiguration(HandlerMethod handlerMethod) {
			HandlerMethod original = handlerMethod.getResolvedFromHandlerMethod();
			return this.corsLookup.get(original != null ? original : handlerMethod);
		}

		/**
		 * Acquire the read lock when using getMappings and getMappingsByUrl.
		 */
		public void acquireReadLock() {
			this.readWriteLock.readLock().lock();
		}

		/**
		 * Release the read lock after using getMappings and getMappingsByUrl.
		 */
		public void releaseReadLock() {
			this.readWriteLock.readLock().unlock();
		}

		public void register(T mapping, Object handler, Method method) {
			this.readWriteLock.writeLock().lock();
			try {
				HandlerMethod handlerMethod = createHandlerMethod(handler, method);
				assertUniqueMethodMapping(handlerMethod, mapping);
				this.mappingLookup.put(mapping, handlerMethod);

				List<String> directUrls = getDirectUrls(mapping);
				for (String url : directUrls) {
					this.urlLookup.add(url, mapping);
				}

				String name = null;
				if (getNamingStrategy() != null) {
					name = getNamingStrategy().getName(handlerMethod, mapping);
					addMappingName(name, handlerMethod);
				}

				CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
				if (corsConfig != null) {
					this.corsLookup.put(handlerMethod, corsConfig);
				}

				this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
			}
			finally {
				this.readWriteLock.writeLock().unlock();
			}
		}

		private void assertUniqueMethodMapping(HandlerMethod newHandlerMethod, T mapping) {
			HandlerMethod handlerMethod = this.mappingLookup.get(mapping);
			if (handlerMethod != null && !handlerMethod.equals(newHandlerMethod)) {
				throw new IllegalStateException(
						"Ambiguous mapping. Cannot map '" +	newHandlerMethod.getBean() + "' method \n" +
						newHandlerMethod + "\nto " + mapping + ": There is already '" +
						handlerMethod.getBean() + "' bean method\n" + handlerMethod + " mapped.");
			}
		}

		private List<String> getDirectUrls(T mapping) {
			List<String> urls = new ArrayList<>(1);
			for (String path : getMappingPathPatterns(mapping)) {
				if (!getPathMatcher().isPattern(path)) {
					urls.add(path);
				}
			}
			return urls;
		}

		private void addMappingName(String name, HandlerMethod handlerMethod) {
			List<HandlerMethod> oldList = this.nameLookup.get(name);
			if (oldList == null) {
				oldList = Collections.emptyList();
			}

			for (HandlerMethod current : oldList) {
				if (handlerMethod.equals(current)) {
					return;
				}
			}

			List<HandlerMethod> newList = new ArrayList<>(oldList.size() + 1);
			newList.addAll(oldList);
			newList.add(handlerMethod);
			this.nameLookup.put(name, newList);
		}

		public void unregister(T mapping) {
			this.readWriteLock.writeLock().lock();
			try {
				MappingRegistration<T> definition = this.registry.remove(mapping);
				if (definition == null) {
					return;
				}

				this.mappingLookup.remove(definition.getMapping());

				for (String url : definition.getDirectUrls()) {
					List<T> list = this.urlLookup.get(url);
					if (list != null) {
						list.remove(definition.getMapping());
						if (list.isEmpty()) {
							this.urlLookup.remove(url);
						}
					}
				}

				removeMappingName(definition);

				this.corsLookup.remove(definition.getHandlerMethod());
			}
			finally {
				this.readWriteLock.writeLock().unlock();
			}
		}

		private void removeMappingName(MappingRegistration<T> definition) {
			String name = definition.getMappingName();
			if (name == null) {
				return;
			}
			HandlerMethod handlerMethod = definition.getHandlerMethod();
			List<HandlerMethod> oldList = this.nameLookup.get(name);
			if (oldList == null) {
				return;
			}
			if (oldList.size() <= 1) {
				this.nameLookup.remove(name);
				return;
			}
			List<HandlerMethod> newList = new ArrayList<>(oldList.size() - 1);
			for (HandlerMethod current : oldList) {
				if (!current.equals(handlerMethod)) {
					newList.add(current);
				}
			}
			this.nameLookup.put(name, newList);
		}
	}