SpringMVC源码-解析视图

DispatcherServlet.applyDefaultViewName(HttpServletRequest request, @Nullable ModelAndView mv)

private void applyDefaultViewName(HttpServletRequest request, @Nullable ModelAndView mv) throws Exception {
	if (mv != null && !mv.hasView()) {
		String defaultViewName = getDefaultViewName(request);
		if (defaultViewName != null) {
			mv.setViewName(defaultViewName);
		}
	}
}

	protected String getDefaultViewName(HttpServletRequest request) throws Exception {
	return (this.viewNameTranslator != null ? this.viewNameTranslator.getViewName(request) : null);
}

    //DefaultRequestToViewNameTranslator
    public String getViewName(HttpServletRequest request) {
	String path = ServletRequestPathUtils.getCachedPathValue(request);
	return (this.prefix + transformPath(path) + this.suffix);
}

如果没有视图则转换视图名。

DispatcherServlet.processDispatchResult(HttpServletRequest request, HttpServletResponse response,@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,@Nullable Exception exception)

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
		@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
		@Nullable Exception exception) throws Exception {

	boolean errorView = false;

	if (exception != null) {
		if (exception instanceof ModelAndViewDefiningException) {
			logger.debug("ModelAndViewDefiningException encountered", exception);
			mv = ((ModelAndViewDefiningException) exception).getModelAndView();
		}
		else {
			Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
			mv = processHandlerException(request, response, handler, exception);
			errorView = (mv != null);
		}
	}

	// Did the handler return a view to render?
	if (mv != null && !mv.wasCleared()) {
		render(mv, request, response);
		if (errorView) {
			WebUtils.clearErrorRequestAttributes(request);
		}
	}
	else {
		if (logger.isTraceEnabled()) {
			logger.trace("No view rendering, null ModelAndView returned.");
		}
	}

	if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
		// Concurrent handling started during a forward
		return;
	}

	if (mappedHandler != null) {
		// Exception (if any) is already handled..
		mappedHandler.triggerAfterCompletion(request, response, null);
	}
}

1、如果有异常调用processHandlerException处理异常
2、render渲染视图

DispatcherServlet.render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response)

protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
	// Determine locale for request and apply it to the response.
	Locale locale =
			(this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
	response.setLocale(locale);

	View view;
	String viewName = mv.getViewName();
	if (viewName != null) {
		// We need to resolve the view name.
		view = resolveViewName(viewName, 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() + "'");
		}
	}

	// Delegate to the View object for rendering.
	if (logger.isTraceEnabled()) {
		logger.trace("Rendering view [" + view + "] ");
	}
	try {
		if (mv.getStatus() != null) {
			response.setStatus(mv.getStatus().value());
		}
		view.render(mv.getModelInternal(), request, response);
	}
	catch (Exception ex) {
		if (logger.isDebugEnabled()) {
			logger.debug("Error rendering view [" + view + "]", ex);
		}
		throw ex;
	}
}

1、获取Locale并将Locale设置到HttpServletResponse
2、如果视图名不等于null调用resolveViewName解析视图名否则获取视图
3、视图对象渲染视图

DispatcherServlet.resolveViewName(String viewName, @Nullable Map<String, Object> model,Locale locale, HttpServletRequest request)

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

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

视图解析器解析视图。

InternalResourceViewResolver

AbstractCachingViewResolver.resolveViewName(String viewName, Locale locale)

public View resolveViewName(String viewName, Locale locale) throws Exception {
	if (!isCache()) {
		return createView(viewName, locale);
	}
	else {
		Object cacheKey = getCacheKey(viewName, locale);
		View view = this.viewAccessCache.get(cacheKey);
		if (view == null) {
			synchronized (this.viewCreationCache) {
				view = this.viewCreationCache.get(cacheKey);
				if (view == null) {
					// Ask the subclass to create the View object.
					view = createView(viewName, locale);
					if (view == null && this.cacheUnresolved) {
						view = UNRESOLVED_VIEW;
					}
					if (view != null && this.cacheFilter.filter(view, viewName, locale)) {
						this.viewAccessCache.put(cacheKey, view);
						this.viewCreationCache.put(cacheKey, view);
					}
				}
			}
		}
		else {
			if (logger.isTraceEnabled()) {
				logger.trace(formatKey(cacheKey) + "served from cache");
			}
		}
		return (view != UNRESOLVED_VIEW ? view : null);
	}
}

如果没有缓存视图则创建视图。

UrlBasedViewResolver.createView(String viewName, Locale locale)

protected View createView(String viewName, Locale locale) throws Exception {
	// If this resolver is not supposed to handle the given view,
	// return null to pass on to the next resolver in the chain.
	if (!canHandle(viewName, locale)) {
		return null;
	}

	// Check for special "redirect:" prefix.
	if (viewName.startsWith(REDIRECT_URL_PREFIX)) {
		String redirectUrl = viewName.substring(REDIRECT_URL_PREFIX.length());
		RedirectView view = new RedirectView(redirectUrl,
				isRedirectContextRelative(), isRedirectHttp10Compatible());
		String[] hosts = getRedirectHosts();
		if (hosts != null) {
			view.setHosts(hosts);
		}
		return applyLifecycleMethods(REDIRECT_URL_PREFIX, view);
	}

	// Check for special "forward:" prefix.
	if (viewName.startsWith(FORWARD_URL_PREFIX)) {
		String forwardUrl = viewName.substring(FORWARD_URL_PREFIX.length());
		InternalResourceView view = new InternalResourceView(forwardUrl);
		return applyLifecycleMethods(FORWARD_URL_PREFIX, view);
	}

	// Else fall back to superclass implementation: calling loadView.
	return super.createView(viewName, locale);
}

1、判断是否支持解析视图，不支持则返回
2、处理redirect
3、处理forward
4、调用super.createView

AbstractCachingViewResolver.createView(String viewName, Locale locale)

protected View createView(String viewName, Locale locale) throws Exception {
	return loadView(viewName, locale);
}

AbstractCachingViewResolver.loadView(String viewName, Locale locale)

	protected View loadView(String viewName, Locale locale) throws Exception {
	AbstractUrlBasedView view = buildView(viewName);
	View result = applyLifecycleMethods(viewName, view);
	return (view.checkResource(locale) ? result : null);
}

1、构建视图，创建视图对象，并将视图名和前缀，后缀组合，设置属性
2、applyLifecycleMethods将视图对象执行beanFactory.initializeBean方法

原文地址：http://www.cnblogs.com/shigongp/p/16862062.html