在自動配置類中EnableWebMvcConfiguration， 我們可以找到一個處理類
@Bean
@Primary
@Override
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
// Must be @Primary for MvcUriComponentsBuilder to work
return super.requestMappingHandlerMapping();
}
RequestMappingHandlerMapping實現了 InitializingBean#afterPropertiesSet方法， 在該方法中將處理探測requestMappingHandlerMapping的工作， 具體細節可以仔細研究源碼，如下：
// Handler method detection
/**
* Detects handler methods at initialization.
* @see #initHandlerMethods
*/
@Override
public void afterPropertiesSet() {
initHandlerMethods();
}
/**
* Scan beans in the ApplicationContext, detect and register handler methods.
* @see #getCandidateBeanNames()
* @see #processCandidateBean
* @see #handlerMethodsInitialized
*/
protected void initHandlerMethods() {
for (String beanName : getCandidateBeanNames()) {
if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
processCandidateBean(beanName);
}
}
handlerMethodsInitialized(getHandlerMethods());
}
/**
* Determine the names of candidate beans in the application context.
* @since 5.1
* @see #setDetectHandlerMethodsInAncestorContexts
* @see BeanFactoryUtils#beanNamesForTypeIncludingAncestors
*/
protected String[] getCandidateBeanNames() {
return (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :
obtainApplicationContext().getBeanNamesForType(Object.class));
}
/**
* Determine the type of the specified candidate bean and call
* {@link #detectHandlerMethods} if identified as a handler type.
* <p>This implementation avoids bean creation through checking
* {@link org.springframework.beans.factory.BeanFactory#getType}
* and calling {@link #detectHandlerMethods} with the bean name.
* @param beanName the name of the candidate bean
* @since 5.1
* @see #isHandler
* @see #detectHandlerMethods
*/
protected void processCandidateBean(String beanName) {
Class<?> beanType = null;
try {
beanType = obtainApplicationContext().getType(beanName);
}
catch (Throwable ex) {
// An unresolvable bean type, probably from a lazy bean - let's ignore it.
if (logger.isTraceEnabled()) {
logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
}
}
if (beanType != null && isHandler(beanType)) {
detectHandlerMethods(beanName);
}
}
/**
* Look for handler methods in the specified handler bean.
* @param handler either a bean name or an actual handler instance
* @see #getMappingForMethod
*/
protected void detectHandlerMethods(Object handler) {
Class<?> handlerType = (handler instanceof String ?
obtainApplicationContext().getType((String) handler) : handler.getClass());
if (handlerType != null) {
Class<?> userType = ClassUtils.getUserClass(handlerType);
Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
(MethodIntrospector.MetadataLookup<T>) method -> {
try {
return getMappingForMethod(method, userType);
}
catch (Throwable ex) {
throw new IllegalStateException("Invalid mapping on handler class [" +
userType.getName() + "]: " + method, ex);
}
});
if (logger.isTraceEnabled()) {
logger.trace(formatMappings(userType, methods));
}
methods.forEach((method, mapping) -> {
Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
registerHandlerMethod(handler, invocableMethod, mapping);
});
}
}
private String formatMappings(Class<?> userType, Map<Method, T> methods) {
String formattedType = Arrays.stream(ClassUtils.getPackageName(userType).split("\\."))
.map(p -> p.substring(0, 1))
.collect(Collectors.joining(".", "", ".")) + userType.getSimpleName();
Function<Method, String> methodFormatter = method -> Arrays.stream(method.getParameterTypes())
.map(Class::getSimpleName)
.collect(Collectors.joining(",", "(", ")"));
return methods.entrySet().stream()
.map(e -> {
Method method = e.getKey();
return e.getValue() + ": " + method.getName() + methodFormatter.apply(method);
})
.collect(Collectors.joining("\n\t", "\n\t" + formattedType + ":" + "\n\t", ""));
}
/**
* Register a handler method and its unique mapping. Invoked at startup for
* each detected handler method.
* @param handler the bean name of the handler or the handler instance
* @param method the method to register
* @param mapping the mapping conditions associated with the handler method
* @throws IllegalStateException if another method was already registered
* under the same mapping
*/
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}
到這裏 ， 我們算是找到了 url與handler映射的處理機制；
那麼，servlet請求的處理流程 在DispatchServlet中又是怎樣的呢， 其實瞭解了上面的處理機制， 這個問題相對簡單多了，作爲servlet ， 基本接口都是實現了servlet的service方法的 ， 那麼DispatchServlet也不例外 ，實現了 service方法，那麼後續處理就不在累述了， 具體可以看代碼如下：
/**
* Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}
* for the actual dispatching.
*/
@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
logRequest(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);
}
}
}
}
private void logRequest(HttpServletRequest request) {
LogFormatUtils.traceDebug(logger, traceOn -> {
String params;
if (isEnableLoggingRequestDetails()) {
params = request.getParameterMap().entrySet().stream()
.map(entry -> entry.getKey() + ":" + Arrays.toString(entry.getValue()))
.collect(Collectors.joining(", "));
}
else {
params = (request.getParameterMap().isEmpty() ? "" : "masked");
}
String queryString = request.getQueryString();
String queryClause = (StringUtils.hasLength(queryString) ? "?" + queryString : "");
String dispatchType = (!request.getDispatcherType().equals(DispatcherType.REQUEST) ?
"\"" + request.getDispatcherType().name() + "\" dispatch for " : "");
String message = (dispatchType + request.getMethod() + " \"" + getRequestUri(request) +
queryClause + "\", parameters={" + params + "}");
if (traceOn) {
List<String> values = Collections.list(request.getHeaderNames());
String headers = values.size() > 0 ? "masked" : "";
if (isEnableLoggingRequestDetails()) {
headers = values.stream().map(name -> name + ":" + Collections.list(request.getHeaders(name)))
.collect(Collectors.joining(", "));
}
return message + ", headers={" + headers + "} in DispatcherServlet '" + getServletName() + "'";
}
else {
return message;
}
});
}
/**
* Process the actual dispatching to the handler.
* <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
* The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
* to find the first that supports the handler class.
* <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
* themselves to decide which methods are acceptable.
* @param request current HTTP request
* @param response current HTTP response
* @throws Exception in case of any kind of processing failure
*/
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.
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
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 (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
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);
}
}
}
}
好了 ， 就寫這麼多吧 ， 這個分析略顯簡陋了 ，希望能幫助你 ， 如果有疏漏 ， 歡迎留言指正。
