Spring MVC 的核心类DispatcherServlet入口为onRefresh()方法，而onRefresh（）方法有直接调用了initStrategies（）方法。代码如下：

/**
     * Initialize the strategy objects that this servlet uses.
     * <p>May be overridden in subclasses in order to initialize further strategy objects.
     */
    protected void initStrategies(ApplicationContext context) {
        initMultipartResolver(context);
        initLocaleResolver(context);
        initThemeResolver(context);
        initHandlerMappings(context);
        initHandlerAdapters(context);
        initHandlerExceptionResolvers(context);
        initRequestToViewNameTranslator(context);
        initViewResolvers(context);
        initFlashMapManager(context);
    }

HandlerMapping

它的作用是根据请求（request）找到相应的Handler和Intercepters。HandlerMapping接口中只有一个getHandler()方法。对应的文档如下：

/**
     * Return a handler and any interceptors for this request. The choice may be made
     * on request URL, session state, or any factor the implementing class chooses.
     * <p>The returned HandlerExecutionChain contains a handler Object, rather than
     * even a tag interface, so that handlers are not constrained in any way.
     * For example, a HandlerAdapter could be written to allow another framework's
     * handler objects to be used.
     * <p>Returns {@code null} if no match was found. This is not an error.
     * The DispatcherServlet will query all registered HandlerMapping beans to find
     * a match, and only decide there is an error if none can find a handler.
     * @param request current HTTP request
     * @return a HandlerExecutionChain instance containing handler object and
     * any interceptors, or {@code null} if no mapping found
     * @throws Exception if there is an internal error
     */
    HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;

我们也可以实现HandlerMapping接口，Override getHandler()方法自己定义一个MyHandlerMapping。

public class MyHandlerMapping implements HandlerMapping{
     @Override
     public HandlerExecutionChain getHandler(HttpServletRequest request)throws Exception{
         String mothed = request.getMethod();
          if(mothed.equalsIgnoreCase("Get")){
               return get方法对应的Handler;
          }else{
               return 其他方法对应的Handler;
          } 
          return null;
     }
}

通过配置<bean>方式注册到spring容器中。

HandlerAdapter

HandlerMapping返回处理请求的Controller实例后，需要一个帮助定位具体请求方法的处理类，这个类就是HandlerAdapter，HandlerAdapter是处理器适配器，Spring MVC通过HandlerAdapter来实际调用处理方法。HandlerAdapter定义了如何处理请求的策略，通过请求url、请求Method和处理器的RequestMapping定义，最终确定使用处理类的哪个方法来处理请求，并检查处理类相应处理方法的参数以及相关的Annotation配置，确定如何转换需要的参数传入调用方法，并最终调用返回ModelAndView。HandlerAdapter接口的三个方法如下：

/**
 * MVC framework SPI, allowing parameterization of the core MVC workflow.
 *
 * <p>Interface that must be implemented for each handler type to handle a request.
 * This interface is used to allow the {@link DispatcherServlet} to be indefinitely
 * extensible. The {@code DispatcherServlet} accesses all installed handlers through
 * this interface, meaning that it does not contain code specific to any handler type.
 *
 * <p>Note that a handler can be of type {@code Object}. This is to enable
 * handlers from other frameworks to be integrated with this framework without
 * custom coding, as well as to allow for annotation-driven handler objects that
 * do not obey any specific Java interface.
 *
 * <p>This interface is not intended for application developers. It is available
 * to handlers who want to develop their own web workflow.
 *
 * <p>Note: {@code HandlerAdapter} implementors may implement the {@link
 * org.springframework.core.Ordered} interface to be able to specify a sorting
 * order (and thus a priority) for getting applied by the {@code DispatcherServlet}.
 * Non-Ordered instances get treated as lowest priority.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter
 * @see org.springframework.web.servlet.handler.SimpleServletHandlerAdapter
 */
public interface HandlerAdapter {

    /**
     * Given a handler instance, return whether or not this {@code HandlerAdapter}
     * can support it. Typical HandlerAdapters will base the decision on the handler
     * type. HandlerAdapters will usually only support one handler type each.
     * <p>A typical implementation:
     * <p>{@code
     * return (handler instanceof MyHandler);
     * }
     * @param handler handler object to check
     * @return whether or not this object can use the given handler
     */
    boolean supports(Object handler);

    /**
     * Use the given handler to handle this request.
     * The workflow that is required may vary widely.
     * @param request current HTTP request
     * @param response current HTTP response
     * @param handler handler to use. This object must have previously been passed
     * to the {@code supports} method of this interface, which must have
     * returned {@code true}.
     * @throws Exception in case of errors
     * @return ModelAndView object with the name of the view and the required
     * model data, or {@code null} if the request has been handled directly
     */
    ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;

    /**
     * Same contract as for HttpServlet's {@code getLastModified} method.
     * Can simply return -1 if there's no support in the handler class.
     * @param request current HTTP request
     * @param handler handler to use
     * @return the lastModified value for the given handler
     * @see javax.servlet.http.HttpServlet#getLastModified
     * @see org.springframework.web.servlet.mvc.LastModified#getLastModified
     */
    long getLastModified(HttpServletRequest request, Object handler);

}

通过配置<bean>方式注册到spring容器中。

HandlerExceptionResolver

/**
 * Interface to be implemented by objects than can resolve exceptions thrown
 * during handler mapping or execution, in the typical case to error views.
 * Implementors are typically registered as beans in the application context.
 *
 * <p>Error views are analogous to the error page JSPs, but can be used with
 * any kind of exception including any checked exception, with potentially
 * fine-granular mappings for specific handlers.
 *
 * @author Juergen Hoeller
 * @since 22.11.2003
 */
public interface HandlerExceptionResolver {

    /**
     * Try to resolve the given exception that got thrown during on handler execution,
     * returning a ModelAndView that represents a specific error page if appropriate.
     * <p>The returned ModelAndView may be {@linkplain ModelAndView#isEmpty() empty}
     * to indicate that the exception has been resolved successfully but that no view
     * should be rendered, for instance by setting a status code.
     * @param request current HTTP request
     * @param response current HTTP response
     * @param handler the executed handler, or {@code null} if none chosen at the
     * time of the exception (for example, if multipart resolution failed)
     * @param ex the exception that got thrown during handler execution
     * @return a corresponding ModelAndView to forward to,
     * or {@code null} for default processing
     */
    ModelAndView resolveException(
             HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex);

}

ViewResolver

ViewResolver负责将String类型的逻辑视图和Locale解析我View类型的视图。它主要有一个方法，如下：

/**
     * Resolve the given view by name.
     * <p>Note: To allow for ViewResolver chaining, a ViewResolver should
     * return {@code null} if a view with the given name is not defined in it.
     * However, this is not required: Some ViewResolvers will always attempt
     * to build View objects with the given name, unable to return {@code null}
     * (rather throwing an exception when View creation failed).
     * @param viewName name of the view to resolve
     * @param locale Locale in which to resolve the view.
     * ViewResolvers that support internationalization should respect this.
     * @return the View object, or {@code null} if not found
     * (optional, to allow for ViewResolver chaining)
     * @throws Exception if the view cannot be resolved
     * (typically in case of problems creating an actual View object)
     */
    View resolveViewName(String viewName, Locale locale) throws Exception;

RequestToViewNameTranslator

ViewResolver是通过viewName 来查找View的，但有些Handler处理完后，并没有设置View或者viewName，这是就需要从request来获取View了，如何从request来获取view呢？那就是RequestToViewNameTranslator所做的事情了。此接口中只有一个方法，如下：

/**
     * Translate the given {@link HttpServletRequest} into a view name.
     * @param request the incoming {@link HttpServletRequest} providing
     * the context from which a view name is to be resolved
     * @return the view name (or {@code null} if no default found)
     * @throws Exception if view name translation fails
     */
    String getViewName(HttpServletRequest request) throws Exception;

LocaleResolver

ViewResolver (视图解析器)在解析视图的时候需要两个参数viewName和Locale。viewName可以通过Handler处理后获得或者通过RequestToViewNameTranslator从request中获取。Local从哪儿来呢？LocaleResolver可以从request中获取Locale。LocaleResolver接口的方法，如下：

/**
 * Interface for web-based locale resolution strategies that allows for
 * both locale resolution via the request and locale modification via
 * request and response.
 *
 * <p>This interface allows for implementations based on request, session,
 * cookies, etc. The default implementation is
 * {@link org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver},
 * simply using the request's locale provided by the respective HTTP header.
 *
 * <p>Use {@link org.springframework.web.servlet.support.RequestContext#getLocale()}
 * to retrieve the current locale in controllers or views, independent
 * of the actual resolution strategy.
 *
 * <p>Note: As of Spring 4.0, there is an extended strategy interface
 * called {@link LocaleContextResolver}, allowing for resolution of
 * a {@link org.springframework.context.i18n.LocaleContext} object,
 * potentially including associated time zone information. Spring's
 * provided resolver implementations implement the extended
 * {@link LocaleContextResolver} interface wherever appropriate.
 *
 */
public interface LocaleResolver {

    /**
     * Resolve the current locale via the given request. Can return a default locale as
     * fallback in any case.
     * @param request the request to resolve the locale for
     * @return the current locale (never {@code null})
     */
    Locale resolveLocale(HttpServletRequest request);

    /**
     * Set the current locale to the given one.
     * @param request the request to be used for locale modification
     * @param response the response to be used for locale modification
     * @param locale the new locale, or {@code null} to clear the locale
     * @throws UnsupportedOperationException if the LocaleResolver implementation does not
     * support dynamic changing of the locale
     */
    void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale);

}

ThemeResolver

/**
 * Interface for web-based theme resolution strategies that allows for
 * both theme resolution via the request and theme modification via
 * request and response.
 *
 * <p>This interface allows for implementations based on session,
 * cookies, etc. The default implementation is
 * {@link org.springframework.web.servlet.theme.FixedThemeResolver},
 * simply using a configured default theme.
 *
 * <p>Note that this resolver is only responsible for determining the
 * current theme name. The Theme instance for the resolved theme name
 * gets looked up by DispatcherServlet via the respective ThemeSource,
 * i.e. the current WebApplicationContext.
 *
 * <p>Use {@link org.springframework.web.servlet.support.RequestContext#getTheme()}
 * to retrieve the current theme in controllers or views, independent
 * of the actual resolution strategy.
 */
public interface ThemeResolver {

    /**
     * Resolve the current theme name via the given request.
     * Should return a default theme as fallback in any case.
     * @param request request to be used for resolution
     * @return the current theme name
     */
    String resolveThemeName(HttpServletRequest request);

    /**
     * Set the current theme name to the given one.
     * @param request request to be used for theme name modification
     * @param response response to be used for theme name modification
     * @param themeName the new theme name
     * @throws UnsupportedOperationException if the ThemeResolver implementation
     * does not support dynamic changing of the theme
     */
    void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName);

}

FlashMapManager

/**
 * A strategy interface for retrieving and saving FlashMap instances.
 * See {@link FlashMap} for a general overview of flash attributes.
 */
public interface FlashMapManager {

    /**
     * Find a FlashMap saved by a previous request that matches to the current
     * request, remove it from underlying storage, and also remove other
     * expired FlashMap instances.
     * <p>This method is invoked in the beginning of every request in contrast
     * to {@link #saveOutputFlashMap}, which is invoked only when there are
     * flash attributes to be saved - i.e. before a redirect.
     * @param request the current request
     * @param response the current response
     * @return a FlashMap matching the current request or {@code null}
     */
    FlashMap retrieveAndUpdate(HttpServletRequest request, HttpServletResponse response);

    /**
     * Save the given FlashMap, in some underlying storage and set the start
     * of its expiration period.
     * <p><strong>NOTE:</strong> Invoke this method prior to a redirect in order
     * to allow saving the FlashMap in the HTTP session or in a response
     * cookie before the response is committed.
     * @param flashMap the FlashMap to save
     * @param request the current request
     * @param response the current response
     */
    void saveOutputFlashMap(FlashMap flashMap, HttpServletRequest request, HttpServletResponse response);

}