SpringMVC九⼤组件初始化

在DispatcherServlet中定义了九个属性，每⼀个属性都对应⼀种组件

九⼤组件都是定义了接⼝，接⼝其实就是定义了该组件的规范，⽐如ViewResolver、HandlerAdapter等都是接⼝

/** MultipartResolver used by this servlet. */
// 多部件解析器
@Nullable
private MultipartResolver multipartResolver;
/** LocaleResolver used by this servlet. */
// 区域化 国际化解析器
@Nullable
private LocaleResolver localeResolver;
/** ThemeResolver used by this servlet. */
// 主题解析器
@Nullable
private ThemeResolver themeResolver;
/** List of HandlerMappings used by this servlet. */
// 处理器映射器组件
@Nullable
private List<HandlerMapping> handlerMappings;
/** List of HandlerAdapters used by this servlet. */
// 处理器适配器组件
@Nullable
private List<HandlerAdapter> handlerAdapters;
/** List of HandlerExceptionResolvers used by this servlet. */
// 异常解析器组件
@Nullable
private List<HandlerExceptionResolver> handlerExceptionResolvers;
/** RequestToViewNameTranslator used by this servlet. */
// 默认视图名转换器组件
@Nullable
private RequestToViewNameTranslator viewNameTranslator;
/** FlashMapManager used by this servlet. */
// flash属性管理组件
@Nullable
private FlashMapManager flashMapManager;
/** List of ViewResolvers used by this servlet. */
// 视图解析器
@Nullable
private List<ViewResolver> viewResolvers;

九⼤组件的初始化时机

DispatcherServlet中的onRefresh()，该⽅法中初始化了九⼤组件

观察其中的⼀个组件initHandlerMappings(context)

private void initHandlerMappings(ApplicationContext context) {
		this.handlerMappings = null;

		if (this.detectAllHandlerMappings) {
			// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
			// 找到所有的HandlerMapping /根据HandlerMapping.class类型从IOC容器中找
			Map<String, HandlerMapping> matchingBeans =
					BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
			if (!matchingBeans.isEmpty()) {
				this.handlerMappings = new ArrayList<>(matchingBeans.values());
				// We keep HandlerMappings in sorted order.
				AnnotationAwareOrderComparator.sort(this.handlerMappings);
			}
		}
		else {
			try {
				// 否则在ioc中按照固定名称“handlerMapping”去找
				HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
				this.handlerMappings = Collections.singletonList(hm);
			}
			catch (NoSuchBeanDefinitionException ex) {
				// Ignore, we'll add a default HandlerMapping later.
			}
		}

		// Ensure we have at least one HandlerMapping, by registering
		// a default HandlerMapping if no other mappings are found.
		if (this.handlerMappings == null) {
			// 最后还为空则按照默认策略生成
			this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
			if (logger.isTraceEnabled()) {
				logger.trace("No HandlerMappings declared for servlet '" + getServletName() +
						"': using default strategies from DispatcherServlet.properties");
			}
		}
	}

如果按照类型和按照固定id从ioc容器中找不到对应组件，则会按照默认策略进⾏注册初始化，默认策略在DispatcherServlet.properties⽂件中配置

根据配置文件中的默认类，对HandlerMapping进行初始化赋值。配置文件对八个组件进行默认配置，multipartResolver没有配置

多部件解析器的初始化必须按照id注册对象（multipartResolver）

所以我们上传文件，在配置多部件解析器时， id一定要是：multipartResolver

来源：CSDN

作者：李不烦

链接：https://blog.csdn.net/LWYYYYYY/article/details/104814861

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初始化