现在来讲解DispatcherServletDispatcherServlet的最后一步：视图渲染。视图渲染的过程是在获取到ModelAndView后的过程。
视图渲染的过程：
doService()--->doDispatch()--->processDispatchResult()--->render()
processDispatchResult():主要处理异常、请求状态及触发请求完成事件,图的渲染工作交给了render().
render()渲染过程如下：
1. 判断ModelAndView中view是否为view name，没有获取其实例对象：如果是根据name，如果是则需要调用resolveViewName从视图解析器获取对应的视图(View)对象；否则ModelAndView中使用getview方法获取view对象。
2. 然后调用view的render()方法。
具体代码如下：
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/**
* Render the given ModelAndView.
*
This is the last stage in handling a request. It may involve resolving the view by name.
* @param mv the ModelAndView to render
* @param request current HTTP servlet request
* @param response current HTTP servlet response
* @throws ServletException if view is missing or cannot be resolved
* @throws Exception if there's a problem rendering the view
*/
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.resolveLocale(request);
response.setLocale(locale);
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() + "'");
}
}
// Delegate to the View object for rendering.
if (logger.isDebugEnabled()) {
logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'");
}
try {
view.render(mv.getModelInternal(), request, response);
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" +
getServletName() + "'", ex);
}
throw ex;
}
}
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那么view 是如何渲染的？我们来看看view的定义：
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org.springframework.web.servlet
Interface View
All Known Subinterfaces:
SmartView
All Known Implementing Classes:
AbstractAtomFeedView, AbstractExcelView, AbstractFeedView, AbstractJ
asperReportsSingleFormatView, AbstractJasperReportsView, AbstractJExcelView, AbstractPdfStamperView, AbstractPdfView, AbstractRssFeedView, AbstractTemplateView, AbstractUrlBasedView, AbstractView, ConfigurableJasperReportsView, FreeMarkerView, InternalResourceView, JasperReportsCsvView, JasperReportsHtmlView, JasperReportsMultiFormatView, JasperReportsPdfView, JasperReportsXlsView, JstlView, MappingJackson2JsonView, MappingJacksonJsonView, MarshallingView, RedirectView, TilesView, T