SpringMVC源碼情操陶冶-AbstractHandlerMethodMapping

承接前文SpringMVC源碼情操陶冶-AbstractHandlerMapping，本文將介紹如何注冊HandlerMethod對象作為handler

類結構瞧一瞧

public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean{}

此為抽象方法，並實現了initializingBean接口，其實主要的注冊操作則是通過afterPropertiesSet()接口方法來調用的

AbstractHandlerMethodMapping#afterPropertiesSet()-初始化HandlerMethod對象

源碼奉上

	@Override
	public void afterPropertiesSet() {
		initHandlerMethods();
	}

轉而看initHandlerMethods()，觀察是如何實現加載HandlerMethod

	
	protected void initHandlerMethods() {
		//獲取springmvc上下文的所有注冊的bean
		String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
				BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
				getApplicationContext().getBeanNamesForType(Object.class));

		for (String beanName : beanNames) {
			if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
				Class<?> beanType = null;
				try {
					beanType = getApplicationContext().getType(beanName);
				}
				catch (Throwable ex) {
					// An unresolvable bean type, probably from a lazy bean - let's ignore it.
					if (logger.isDebugEnabled()) {
						logger.debug("Could not resolve target class for bean with name '" + beanName + "'", ex);
					}
				}
				//isHandler()是抽象方法，主要供子類需要掃描什么類型的bean
				if (beanType != null && isHandler(beanType)) {
					//解析其中的HandlerMethod進行注冊
					detectHandlerMethods(beanName);
				}
			}
		}
		//抽象方法，目前尚無實現
		handlerMethodsInitialized(getHandlerMethods());
	}

接下來稍微分析springmvc是如何解析bean並獲取其中的HandlerMethod

AbstractHandlerMethodMapping#detectHandlerMethods()解析

源碼奉上

	protected void detectHandlerMethods(final Object handler) {
		Class<?> handlerType = (handler instanceof String ?
				getApplicationContext().getType((String) handler) : handler.getClass());
		//因為有些是CGLIB代理生成的，獲取真實的類
		final Class<?> userType = ClassUtils.getUserClass(handlerType);

		Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
				new MethodIntrospector.MetadataLookup<T>() {
					@Override
					public T inspect(Method method) {
						try {
							//模板方法獲取handlerMethod的mapping屬性
							return getMappingForMethod(method, userType);
						}
						catch (Throwable ex) {
							throw new IllegalStateException("Invalid mapping on handler class [" +
									userType.getName() + "]: " + method, ex);
						}
					}
				});

		//對查找到的HandlerMethod進行注冊，保存至內部類mappingRegistry對象中
		for (Map.Entry<Method, T> entry : methods.entrySet()) {
			//作下判斷，method是否從屬於userType
			Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);
			T mapping = entry.getValue();
			registerHandlerMethod(handler, invocableMethod, mapping);
		}
	}

針對唯一的實現類RequestMappingHandlerMapping，上述的mapping屬性指代的是RequestMappingInfo對象，內部包含@RequestMapping注解的內部屬性，比如method、params、consumes、produces、value以及對應的屬性判斷類

RequestMappingHandlerMapping-唯一實現類

作為HandlerMethod對象的配置者，我們主要觀察其復寫的幾個方法

RequestMappingHandlerMapping#afterPropertiesSet()

代碼奉上

	@Override
	public void afterPropertiesSet() {
		//config為RequestMappingInfo的創建對象
		this.config = new RequestMappingInfo.BuilderConfiguration();
		//設置urlPathHelper默認為UrlPathHelper.class
		this.config.setUrlPathHelper(getUrlPathHelper());
		//默認為AntPathMatcher，路徑匹配校驗器
		this.config.setPathMatcher(getPathMatcher());
		//是否支持后綴補充，默認為true
		this.config.setSuffixPatternMatch(this.useSuffixPatternMatch);
		//是否添加"/"后綴，默認為true
		this.config.setTrailingSlashMatch(this.useTrailingSlashMatch);
		//是否采用mediaType匹配模式，比如.json/.xml模式的匹配，默認為false		
		this.config.setRegisteredSuffixPatternMatch(this.useRegisteredSuffixPatternMatch);
		//mediaType處理類		
		this.config.setContentNegotiationManager(getContentNegotiationManager());
		//調用父類進行HandlerMethod的注冊工作
		super.afterPropertiesSet();
	}

此處如何設置可通過查看博文>>>SpringMVC源碼情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

RequestMappingHandlerMapping#isHandler()-判斷獲取何種類型的Handler

獲取@Controller/@RequestMapping注解下的handler

	@Override
	protected boolean isHandler(Class<?> beanType) {
		//優先匹配@Controller
		return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
				AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
	}

RequestMappingHandlerMapping#getMappingForMethod()-獲取HandlerMethod對應的mapping屬性

此處指的是RequestMappingInfo，主要包含了路徑匹配策略、@RequestMapping屬性匹配策略，簡單源碼奉上

	@Override
	protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
		//對method以及class類都進行創建RequestMappingInfo 
		//因為@RequestMapping可以在方法上/類上應用注解
		RequestMappingInfo info = createRequestMappingInfo(method);
		if (info != null) {
			RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
			if (typeInfo != null) {
				info = typeInfo.combine(info);
			}
		}
		return info;
	}

由代碼可知，其將拼裝Class上的@RequestMapping和Method上的@RequestMapping組裝成RequestMappingInfo對象，其內部的屬性讀者有興趣可自行去分析。

此處對createRequestMappingInfo()方法作下補充

	protected RequestMappingInfo createRequestMappingInfo(
			RequestMapping requestMapping, RequestCondition<?> customCondition) {

		return RequestMappingInfo
				.paths(resolveEmbeddedValuesInPatterns(requestMapping.path()))
				.methods(requestMapping.method())
				.params(requestMapping.params())
				.headers(requestMapping.headers())
				.consumes(requestMapping.consumes())
				.produces(requestMapping.produces())
				.mappingName(requestMapping.name())
				.customCondition(customCondition)
				.options(this.config)
				.build();
	}

小結

• 介紹AbstractHandlerMethodMapping如何創建HandlerMethod，調用者為RequestMappingHandlerMapping，其可通過mvc:annotation-driven注冊，具體可查看>>>SpringMVC源碼情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

• 其中其唯一實現類RequestMappingHandlerMapping主要是獲取@Controller下的@RequestMapping注解的方法將其注冊為HandlerMethod對象，其余的相關信息則注冊為RequestMappingInfo對象供對路徑信息匹配

• 其中如何獲取HandlerMethod查看前言中的鏈接即可