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Springmvc ViewResolver實現的過程？很多新手對此不是很清楚，為了幫助大家解決這個難題，下面小編將為大家詳細講解，有這方面需求的人可以來學習下，希望你能有所收獲。
總結：
ViewResolver 如果要改需要自己注入到容器中并進行修改， springmvc使用的是InterResourceViewResover
view不需要自己改，是springmvc根據return返回值選的
既然看到有ModelAndView直接跳轉jsp的， 有請求轉發的，有重定向的，這里整體是怎么設計的： (@ResponseBody的在此不作展開)
HiController:
@Controller
public class HiController {
@RequestMapping("/hi")
public ModelAndView getHi() {
ModelAndView mav = new ModelAndView("me");
return mav;
}
@RequestMapping("/yes")
public String forwardYes() {
return "forward:patch";
}
@RequestMapping("/no")
public String RedirectNo() {
return "redirect:patch";
}
@ResponseBody
@RequestMapping("/patch")
public String redirectNo() {
return "from forward or redirect request"; // 這種情況沒有view，在這里不討論
}
}主要代碼：
DispatcherServlet.doDispatch(）里的：
DispatcherServlet.render方法：
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); // 1
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); // 2
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Error rendering view [" + view + "]", ex);
}
throw ex;
}
}1. view = resolveViewName()會根據不同的路徑生成不同的view, return mav 會返回JstlView, return "forward:/patch" 會返回InternalResourceView， return "direct:/patch" 會返回IndirectView
2. 不同的view去走不同的view.render()， 根據不同的view重寫abstract void renderMergedOutputModel方法
再來看是如何生成不同的view:[/code][code]view = resolveViewName() 進去，走到
DiapatcherServlet先有ViewResolver這個，用來生成不同的view
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;
}ViewResolver 接口只有一個方法
public interface ViewResolver {
@Nullable
View resolveViewName(String viewName, Locale locale) throws Exception;
}要配置具體的視圖解析器，springMVC中使用的是InterResourceViewResover，InterResourceViewResover 和他的父類UrlBasedViewResolver中都沒有重寫resolveViewName方法，再上一層的父類AbstractCahingViewResolver實現了resolveViewName方法
AbstractCahingViewResolver：
@Override
@Nullable
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);
}
}InterResourceViewResover中沒有createView方法，所以是調用它父類UrlBasedViewResolver的createView方法：
@Override
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); // return "direct:/patch"在這里構造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); // return "forward:/patch" 在這里構造view
}
// Else fall back to superclass implementation: calling loadView.
return super.createView(viewName, locale); // return mav 在這里構造view
}關于ViewResolver的代碼執行順序， 前面分析那么多，這里再打斷點快速驗證一下：
進DispatcherServlet的doDispatch看到就是這個解析器：
斷點放在這里，
然后下一步：
看完上述內容是否對您有幫助呢？如果還想對相關知識有進一步的了解或閱讀更多相關文章，請關注億速云行業資訊頻道，感謝您對億速云的支持。
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