Spring5 源码阅读笔记（5.2.4）processDispatchResult

类 DispatcherServlet

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

	boolean errorView = false;

	//如果异常不为空
	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?
	//视图渲染，响应视图
	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;
	}

	//afterCompletion
	if (mappedHandler != null) {
		mappedHandler.triggerAfterCompletion(request, response, null);
	}
}

跟 render：

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());
		}
		//核心逻辑在这里
		view.render(mv.getModelInternal(), request, response);
	}
	catch (Exception ex) {
		if (logger.isDebugEnabled()) {
			logger.debug("Error rendering view [" + view + "]", ex);
		}
		throw ex;
	}
}

跟 render：
类 View

void render(@Nullable Map<String, ?> model, HttpServletRequest request, HttpServletResponse response)
		throws Exception;

类 AbstractView

@Override
public void render(@Nullable Map<String, ?> model, HttpServletRequest request,
		HttpServletResponse response) throws Exception {

	if (logger.isDebugEnabled()) {
		logger.debug("View " + formatViewName() +
				", model " + (model != null ? model : Collections.emptyMap()) +
				(this.staticAttributes.isEmpty() ? "" : ", static attributes " + this.staticAttributes));
	}

	Map<String, Object> mergedModel = createMergedOutputModel(model, request, response);
	//编码
	prepareResponse(request, response);
	renderMergedOutputModel(mergedModel, getRequestToExpose(request), response);
}

跟 renderMergedOutputModel：

protected abstract void renderMergedOutputModel(
		Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception;

类 InternalResourceView

@Override
protected void renderMergedOutputModel(
		Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {

	//把响应数据设置到request对象中
	// Expose the model object as request attributes.
	exposeModelAsRequestAttributes(model, request);

	// Expose helpers as request attributes, if any.
	exposeHelpers(request);

	//获取到跳转的地址
	// Determine the path for the request dispatcher.
	String dispatcherPath = prepareForRendering(request, response);

	// Obtain a RequestDispatcher for the target resource (typically a JSP).
	RequestDispatcher rd = getRequestDispatcher(request, dispatcherPath);
	if (rd == null) {
		throw new ServletException("Could not get RequestDispatcher for [" + getUrl() +
				"]: Check that the corresponding file exists within your web application archive!");
	}

	// If already included or response already committed, perform include, else forward.
	if (useInclude(request, response)) {
		response.setContentType(getContentType());
		if (logger.isDebugEnabled()) {
			logger.debug("Including [" + getUrl() + "]");
		}
		rd.include(request, response);
	}

	else {
		// Note: The forwarded resource is supposed to determine the content type itself.
		if (logger.isDebugEnabled()) {
			logger.debug("Forwarding to [" + getUrl() + "]");
		}
		rd.forward(request, response);
	}
}