DispatcherServlet中九大组件
/** 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;
DispatcherServlet#onRefresh()初始化九大组件
@Override
protected void onRefresh(ApplicationContext context) {
initStrategies(context);
}
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
initHandlerMappings():初始化handlerMapping
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
//按照HandlerMapping.class类型去ioc容器中找到所有的HandlerMapping
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id(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
//按照默认方式实例化HandlerMapping
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
}
}
}
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
protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
String key = strategyInterface.getName();
String value = defaultStrategies.getProperty(key);
if (value != null) {
String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
List<T> strategies = new ArrayList<>(classNames.length);
for (String className : classNames) {
try {
Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
Object strategy = createDefaultStrategy(context, clazz);
strategies.add((T) strategy);
}
catch (ClassNotFoundException ex) {
throw new BeanInitializationException(
"Could not find DispatcherServlet's default strategy class [" + className +
"] for interface [" + key + "]", ex);
}
catch (LinkageError err) {
throw new BeanInitializationException(
"Error loading DispatcherServlet's default strategy class [" + className +
"] for interface [" + key + "]: problem with class file or dependent class", err);
}
}
return strategies;
}
else {
return new LinkedList<>();
}
}
DispatcherServlet.properties
注意:多部件解析器的初始化必须按照id注册对象(multipartResolver)