Spring ViewResolver

Spring ViewResolver

AbstractCachingViewResolver、XmlViewResolver、ResourceBundleViewResolver、UrlBasedViewResolver、InternalResourceViewResolver、VelocityViewResolver、FreeMarkerViewResolver
、ContentNegotiatingViewResolver

加载

org.springframework.web.servlet.view.ContentNegotiatingViewResolver

问题点：

    是不是所有的ViewResolver都是通过ContentNegotiatingViewResolver这个加载的 --> 不是

    ContentNegotiatingViewResolver起到的作用是什么

    只有一个jspView的时候会不会调用ContentNegotiatingViewResolver

	private void initViewResolvers(ApplicationContext context) {
		this.viewResolvers = null;

		if (this.detectAllViewResolvers) {
			// Find all ViewResolvers in the ApplicationContext, including ancestor contexts.
			Map<String, ViewResolver> matchingBeans =
					BeanFactoryUtils.beansOfTypeIncludingAncestors(context, ViewResolver.class, true, false);
			if (!matchingBeans.isEmpty()) {
				this.viewResolvers = new ArrayList<>(matchingBeans.values());
				// We keep ViewResolvers in sorted order.
				AnnotationAwareOrderComparator.sort(this.viewResolvers);
			}
		}
		else {
			try {
				ViewResolver vr = context.getBean(VIEW_RESOLVER_BEAN_NAME, ViewResolver.class);
				this.viewResolvers = Collections.singletonList(vr);
			}
			catch (NoSuchBeanDefinitionException ex) {
				// Ignore, we'll add a default ViewResolver later.
			}
		}

		// Ensure we have at least one ViewResolver, by registering
		// a default ViewResolver if no other resolvers are found.
		if (this.viewResolvers == null) {
			this.viewResolvers = getDefaultStrategies(context, ViewResolver.class);
			if (logger.isDebugEnabled()) {
				logger.debug("No ViewResolvers found in servlet '" + getServletName() + "': using default");
			}
		}
	}

doDispatch

processDispatchResult

render:

			View view;
			if (mv.isReference()) {
				// We need to resolve the view name.
				view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);
				if (view == null) {
					throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
							"' in servlet with name '" + getServletName() + "'");
				}
			}
			else {
				// No need to lookup: the ModelAndView object contains the actual View object.
				view = mv.getView();
				if (view == null) {
					throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
							"View object in servlet with name '" + getServletName() + "'");
				}
			}

resolveViewName:

	protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale,
			HttpServletRequest request) throws Exception {

		for (ViewResolver viewResolver : this.viewResolvers) {
			View view = viewResolver.resolveViewName(viewName, locale);
			if (view != null) {
				return view;
			}
		}
		return null;
	}