Springmvc ViewResolver设计实现过程解析
作者：圣金巫灵
这篇文章主要介绍了Springmvc ViewResolver设计实现过程解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
总结：
ViewResolver 如果要改需要自己注入到容器中并进行修改， springmvc使用的是InterResourceViewResover
view不需要自己改，是springmvc根据return返回值选的
既然看到有ModelAndView直接跳转jsp的， 有请求转发的，有重定向的，这里整体是怎么设计的： (@ResponseBody的在此不作展开)
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"; // 这种情况没有view，在这里不讨论
}
}
主要代码：
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()会根据不同的路径生成不同的view, return mav 会返回JstlView, return "forward:/patch" 会返回InternalResourceView， return "direct:/patch" 会返回IndirectView
2. 不同的view去走不同的view.render()， 根据不同的view重写abstract void renderMergedOutputModel方法
再来看是如何生成不同的view:[/code][code]view = resolveViewName() 进去，走到
DiapatcherServlet先有ViewResolver这个，用来生成不同的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 接口只有一个方法
public interface ViewResolver {
@Nullable
View resolveViewName(String viewName, Locale locale) throws Exception;
}
要配置具体的视图解析器，springMVC中使用的是InterResourceViewResover，InterResourceViewResover 和他的父类UrlBasedViewResolver中都没有重写resolveViewName方法，再上一层的父类AbstractCahingViewResolver实现了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中没有createView方法，所以是调用它父类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"在这里构造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" 在这里构造view
}
// Else fall back to superclass implementation: calling loadView.
return super.createView(viewName, locale); // return mav 在这里构造view
}
关于ViewResolver的代码执行顺序， 前面分析那么多，这里再打断点快速验证一下：
进DispatcherServlet的doDispatch看到就是这个解析器：
断点放在这里，
然后下一步：
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。