SpringMVC源码情操陶冶-AbstractHandlerMethodMapping

承接前文SpringMVC源码情操陶冶-AbstractHandlerMapping，本文将介绍如何注册HandlerMethod对象作为handler

类结构瞧一瞧

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

此为抽象方法，并实现了initializingBean接口，其实主要的注册操作则是通过afterPropertiesSet()接口方法来调用的

AbstractHandlerMethodMapping#afterPropertiesSet()-初始化HandlerMethod对象

源码奉上

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

转而看initHandlerMethods()，观察是如何实现加载HandlerMethod

	protected void initHandlerMethods() {
		//获取springmvc上下文的所有注册的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，主要供子类需要扫描什么类型的bean
				if (beanType != null && isHandler(beanType)) {
					//解析其中的HandlerMethod进行注册
					detectHandlerMethods(beanName);
				}
			}
		}
		//抽象方法，目前尚无实现
		handlerMethodsInitialized(getHandlerMethods());
	}

接下来稍微分析springmvc是如何解析bean并获取其中的HandlerMethod

AbstractHandlerMethodMapping#detectHandlerMethods()解析

源码奉上

	protected void detectHandlerMethods(final Object handler) {
		Class<?> handlerType = (handler instanceof String ?
				getApplicationContext().getType((String) handler) : handler.getClass());
		//因为有些是CGLIB代理生成的，获取真实的类
		final Class<?> userType = ClassUtils.getUserClass(handlerType);

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

		//对查找到的HandlerMethod进行注册，保存至内部类mappingRegistry对象中
		for (Map.Entry<Method, T> entry : methods.entrySet()) {
			//作下判断，method是否从属于userType
			Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);
			T mapping = entry.getValue();
			registerHandlerMethod(handler, invocableMethod, mapping);
		}
	}

针对唯一的实现类RequestMappingHandlerMapping，上述的mapping属性指代的是RequestMappingInfo对象，内部包含@RequestMapping注解的内部属性，比如method、params、consumes、produces、value以及对应的属性判断类

RequestMappingHandlerMapping-唯一实现类

作为HandlerMethod对象的配置者，我们主要观察其复写的几个方法

RequestMappingHandlerMapping#afterPropertiesSet()

代码奉上

	@Override
	public void afterPropertiesSet() {
		//config为RequestMappingInfo的创建对象
		this.config = new RequestMappingInfo.BuilderConfiguration();
		//设置urlPathHelper默认为UrlPathHelper.class
		this.config.setUrlPathHelper(getUrlPathHelper());
		//默认为AntPathMatcher，路径匹配校验器
		this.config.setPathMatcher(getPathMatcher());
		//是否支持后缀补充，默认为true
		this.config.setSuffixPatternMatch(this.useSuffixPatternMatch);
		//是否添加"/"后缀，默认为true
		this.config.setTrailingSlashMatch(this.useTrailingSlashMatch);
		//是否采用mediaType匹配模式，比如.json/.xml模式的匹配，默认为false
		this.config.setRegisteredSuffixPatternMatch(this.useRegisteredSuffixPatternMatch);
		//mediaType处理类
		this.config.setContentNegotiationManager(getContentNegotiationManager());
		//调用父类进行HandlerMethod的注册工作
		super.afterPropertiesSet();
	}

此处如何设置可通过查看博文>>>SpringMVC源码情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

RequestMappingHandlerMapping#isHandler()-判断获取何种类型的Handler

获取@Controller/@RequestMapping注解下的handler

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

RequestMappingHandlerMapping#getMappingForMethod()-获取HandlerMethod对应的mapping属性

此处指的是RequestMappingInfo，主要包含了路径匹配策略、@RequestMapping属性匹配策略，简单源码奉上

	@Override
	protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
		//对method以及class类都进行创建RequestMappingInfo
		//因为@RequestMapping可以在方法上/类上应用注解
		RequestMappingInfo info = createRequestMappingInfo(method);
		if (info != null) {
			RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
			if (typeInfo != null) {
				info = typeInfo.combine(info);
			}
		}
		return info;
	}

由代码可知，其将拼装Class上的@RequestMapping和Method上的@RequestMapping组装成RequestMappingInfo对象，其内部的属性读者有兴趣可自行去分析。

此处对createRequestMappingInfo()方法作下补充

	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();
	}

小结

• 介绍AbstractHandlerMethodMapping如何创建HandlerMethod，调用者为RequestMappingHandlerMapping，其可通过mvc:annotation-driven注册，具体可查看>>>SpringMVC源码情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

• 其中其唯一实现类RequestMappingHandlerMapping主要是获取@Controller下的@RequestMapping注解的方法将其注册为HandlerMethod对象，其余的相关信息则注册为RequestMappingInfo对象供对路径信息匹配

• 其中如何获取HandlerMethod查看前言中的链接即可