SpringMVC源码剖析1——执行流程
00.SpringMVC执行流程
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01.拦截所有的请求,访问DispatcherServlet
<ignore_js_op>
02.DispatcherServlet原理是一个Servlet,只要是Servlet就走doService方法
下面是DispatcherServlet的doService方法
<ignore_js_op>
02.DispatcherServlet原理是一个Servlet,只要是Servlet就走doService方法
下面是DispatcherServlet的doService方法
[Java]
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protected
void
doService(HttpServletRequest request, HttpServletResponse response)
throws
Exception {
if
(logger.isDebugEnabled()) {
String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ?
" resumed"
:
""
;
logger.debug(
"DispatcherServlet with name '"
+ getServletName() +
"'"
+ resumed +
" processing "
+ request.getMethod() +
" request for ["
+ getRequestUri(request) +
"]"
);
}
// Keep a snapshot of the request attributes in case of an include,
// to be able to restore the original attributes after the include.
Map<String, Object> attributesSnapshot =
null
;
if
(WebUtils.isIncludeRequest(request)) {
attributesSnapshot =
new
HashMap<>();
Enumeration<?> attrNames = request.getAttributeNames();
while
(attrNames.hasMoreElements()) {
String attrName = (String) attrNames.nextElement();
if
(
this
.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {
attributesSnapshot.put(attrName, request.getAttribute(attrName));
}
}
}
// Make framework objects available to handlers and view objects.
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE,
this
.localeResolver);
request.setAttribute(THEME_RESOLVER_ATTRIBUTE,
this
.themeResolver);
request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());
if
(
this
.flashMapManager !=
null
) {
FlashMap inputFlashMap =
this
.flashMapManager.retrieveAndUpdate(request, response);
if
(inputFlashMap !=
null
) {
request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));
}
request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE,
new
FlashMap());
request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE,
this
.flashMapManager);
}
try
{
doDispatch(request, response);
}
finally
{
if
(!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Restore the original attribute snapshot, in case of an include.
if
(attributesSnapshot !=
null
) {
restoreAttributesAfterInclude(request, attributesSnapshot);
}
}
}
}
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前面都没啥用就是给request添加参数
03. doDispatch(request, response);方法
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protected
void
doDispatch(HttpServletRequest request, HttpServletResponse response)
throws
Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler =
null
;
boolean
multipartRequestParsed =
false
;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try
{
ModelAndView mv =
null
;
Exception dispatchException =
null
;
try
{
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request. 这段代码是用来确定调用方法的,是根据路径解析出来的
mappedHandler = getHandler(processedRequest);
if
(mappedHandler ==
null
) {
noHandlerFound(processedRequest, response);
return
;
}
// Determine handler adapter for the current request.
//确定当前请求程序的适配器 [RequestMappingHandlerAdapter也是就@Controller 的适配器
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean
isGet =
"GET"
.equals(method);
if
(isGet ||
"HEAD"
.equals(method)) {
long
lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if
(logger.isDebugEnabled()) {
logger.debug(
"Last-Modified value for ["
+ getRequestUri(request) +
"] is: "
+ lastModified);
}
if
(
new
ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return
;
}
}
if
(!mappedHandler.applyPreHandle(processedRequest, response)) {
return
;
}
// Actually invoke the handler. 通过反射调用相应执行的方法
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if
(asyncManager.isConcurrentHandlingStarted()) {
return
;
}
applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch
(Exception ex) {
dispatchException = ex;
}
catch
(Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException =
new
NestedServletException(
"Handler dispatch failed"
, err);
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch
(Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch
(Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new
NestedServletException(
"Handler processing failed"
, err));
}
finally
{
if
(asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if
(mappedHandler !=
null
) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else
{
// Clean up any resources used by a multipart request.
if
(multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}
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04. mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
此方法主要是调用对应的适配器,然后再通过反射执行对应方法
本来应该调用 RequestHandlerAdapter类中的方法,但是没有,根据继承的关系调用父类, 抽象类 AbstractHandlerMethodAdapter中的方法 handle( )
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public
final
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws
Exception {
return
handleInternal(request, response, (HandlerMethod) handler);
}
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本类
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protected
abstract
ModelAndView handleInternal(HttpServletRequest request,HttpServletResponse response,
HandlerMethod handlerMethod)
throws
Exception;
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然后在 RequestHandlerAdapter中调用 handleInternal( )方法
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protected
ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod)
throws
Exception {
ModelAndView mav;
checkRequest(request);
// Execute invokeHandlerMethod in synchronized block if required.
if
(
this
.synchronizeOnSession) {
HttpSession session = request.getSession(
false
);
if
(session !=
null
) {
Object mutex = WebUtils.getSessionMutex(session);
synchronized
(mutex) {
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else
{
// No HttpSession available -> no mutex necessary
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else
{
// No synchronization on session demanded at all...
mav = invokeHandlerMethod(request, response, handlerMethod);
}
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