摘要:express
SimpleUrlHandlerMapping只是參與Handler的註冊,請求映射時由AbstractUrlHandlerMapping搞定.api
初始化時,經過setMappings(Properties mappings)或者setUrlMap(Map<String, ?> urlMap)設置映射關係,而後經過WebApplicationObjectSupport的initApplicationContext調用registerHandlers進行註冊.緩存
覆寫initApplicationContext方法時,先調用父類實現,而後才調用registerHandlers進行註冊.其中最終的註冊registerHandler實現是由AbstractUrlHandlerMapping實現的.mvc
父類AbstractHandlerMapping繼承了WebApplicationObjectSupport,因此SimpleUrlHandlerMapping能夠經過覆寫initApplicationContext註冊Handler.
註冊Handler前,不忘靠AbstractHandlerMapping來初始化攔截器.
// SimpleUrlHandlerMapping
1 /**
2 * Calls the {@link #registerHandlers} method in addition to the
3 * superclass's initialization.
4 */
5 @Override
6 public void initApplicationContext() throws BeansException {
7 super.initApplicationContext();
8 registerHandlers(this.urlMap);
9 }
initApplicationContext主要是進行攔截器的初始化.
extendInterceptors是留給子類用的擴展接口,暫時沒有使用
detectMappedInterceptors是經過BeanFactoryUtils掃描應用下的所有MappedInterceptor類
initInterceptors初始化特定的攔截器,檢查MappedInterceptor,在須要時適配adaptor HandlerInterceptor
// AbstractHandlerMapping
1 /**
2 * Initializes the interceptors.
3 * @see #extendInterceptors(java.util.List)
4 * @see #initInterceptors()
5 */
6 @Override
7 protected void initApplicationContext() throws BeansException {
8 extendInterceptors(this.interceptors);
9 detectMappedInterceptors(this.mappedInterceptors);
10 initInterceptors();
11 }
// AbstractHandlerMapping
1 /**
2 * Extension hook that subclasses can override to register additional interceptors,
3 * given the configured interceptors (see {@link #setInterceptors}).
4 * <p>Will be invoked before {@link #initInterceptors()} adapts the specified
5 * interceptors into {@link HandlerInterceptor} instances.
6 * <p>The default implementation is empty.
7 * @param interceptors the configured interceptor List (never {@code null}),
8 * allowing to add further interceptors before as well as after the existing
9 * interceptors
10 */
11 protected void extendInterceptors(List<Object> interceptors) {
12 }
springmvc中常常使用BeanFactoryUtils掃描應用下的類來進行初始化.
// AbstractHandlerMapping
1 /**
2 * Detects beans of type {@link MappedInterceptor} and adds them to the list of mapped interceptors.
3 * This is done in addition to any {@link MappedInterceptor}s that may have been provided via
4 * {@link #setInterceptors(Object[])}. Subclasses can override this method to change that.
5 *
6 * @param mappedInterceptors an empty list to add MappedInterceptor types to
7 */
8 protected void detectMappedInterceptors(List<MappedInterceptor> mappedInterceptors) {
9 mappedInterceptors.addAll(
10 BeanFactoryUtils.beansOfTypeIncludingAncestors(
11 getApplicationContext(),MappedInterceptor.class, true, false).values());
12 }
// AbstractHandlerMapping
1 /**
2 * Initialize the specified interceptors, checking for {@link MappedInterceptor}s and adapting
3 * HandlerInterceptors where necessary.
4 * @see #setInterceptors
5 * @see #adaptInterceptor
6 */
7 protected void initInterceptors() {
8 if (!this.interceptors.isEmpty()) {
9 for (int i = 0; i < this.interceptors.size(); i++) {
10 Object interceptor = this.interceptors.get(i);
11 if (interceptor == null) {
12 throw new IllegalArgumentException("Entry number " + i + " in interceptors array is null");
13 }
14 if (interceptor instanceof MappedInterceptor) {
15 mappedInterceptors.add((MappedInterceptor) interceptor);
16 }
17 else {
18 adaptedInterceptors.add(adaptInterceptor(interceptor));
19 }
20 }
21 }
22 }
適配HandlerInterceptor和WebRequestHandlerInterceptorAdapter(什麼是WebRequestHandlerInterceptorAdapter,晚點再說吧,具體看到時候攔截器部分的分析)
// AbstractHandlerMapping
1 /**
2 * Adapt the given interceptor object to the HandlerInterceptor interface.
3 * <p>Supported interceptor types are HandlerInterceptor and WebRequestInterceptor.
4 * Each given WebRequestInterceptor will be wrapped in a WebRequestHandlerInterceptorAdapter.
5 * Can be overridden in subclasses.
6 * @param interceptor the specified interceptor object
7 * @return the interceptor wrapped as HandlerInterceptor
8 * @see org.springframework.web.servlet.HandlerInterceptor
9 * @see org.springframework.web.context.request.WebRequestInterceptor
10 * @see WebRequestHandlerInterceptorAdapter
11 */
12 protected HandlerInterceptor adaptInterceptor(Object interceptor) {
13 if (interceptor instanceof HandlerInterceptor) {
14 return (HandlerInterceptor) interceptor;
15 }
16 else if (interceptor instanceof WebRequestInterceptor) {
17 return new WebRequestHandlerInterceptorAdapter((WebRequestInterceptor) interceptor);
18 }
19 else {
20 throw new IllegalArgumentException("Interceptor type not supported: " + interceptor.getClass().getName());
21 }
22 }
這纔到SimpleUrlHandlerMapping幹活的地方,迭代urlMap調用AbstractUrlHandlerMapping的registerHandler進行註冊
(保障url以"/"開頭就很少說了)
// SimpleUrlHandlerMapping
1 /**
2 * Register all handlers specified in the URL map for the corresponding paths.
3 * @param urlMap Map with URL paths as keys and handler beans or bean names as values
4 * @throws BeansException if a handler couldn't be registered
5 * @throws IllegalStateException if there is a conflicting handler registered
6 */
7 protected void registerHandlers(Map<String, Object> urlMap) throws BeansException {
8 if (urlMap.isEmpty()) {
9 logger.warn("Neither 'urlMap' nor 'mappings' set on SimpleUrlHandlerMapping");
10 }
11 else {
12 for (Map.Entry<String, Object> entry : urlMap.entrySet()) {
13 String url = entry.getKey();
14 Object handler = entry.getValue();
15 // Prepend with slash if not already present.
16 if (!url.startsWith("/")) {
17 url = "/" + url;
18 }
19 // Remove whitespace from handler bean name.
20 if (handler instanceof String) {
21 handler = ((String) handler).trim();
22 }
23 registerHandler(url, handler);
24 }
25 }
26 }
// AbstractUrlHandlerMapping
1 /**
2 * Register the specified handler for the given URL path.
3 * @param urlPath the URL the bean should be mapped to
4 * @param handler the handler instance or handler bean name String
5 * (a bean name will automatically be resolved into the corresponding handler bean)
6 * @throws BeansException if the handler couldn't be registered
7 * @throws IllegalStateException if there is a conflicting handler registered
8 */
9 protected void registerHandler(String urlPath, Object handler) throws BeansException, IllegalStateException {
10 Assert.notNull(urlPath, "URL path must not be null");
11 Assert.notNull(handler, "Handler object must not be null");
12 Object resolvedHandler = handler;
13
14 // Eagerly resolve handler if referencing singleton via name.不是單例同時不是懶加載
15 if (!this.lazyInitHandlers && handler instanceof String) {
16 String handlerName = (String) handler;
17 if (getApplicationContext().isSingleton(handlerName)) {
18 resolvedHandler = getApplicationContext().getBean(handlerName);
19 }
20 }
21
22 Object mappedHandler = this.handlerMap.get(urlPath);// 獲取以前已經匹配的Handler
23 if (mappedHandler != null) {
24 if (mappedHandler != resolvedHandler) {// 若是新匹配獲得的跟以前已解析到的handler不一致,則拋異常
25 throw new IllegalStateException(
26 "Cannot map " + getHandlerDescription(handler) + " to URL path [" + urlPath +
27 "]: There is already " + getHandlerDescription(mappedHandler) + " mapped.");
28 }
29 }
30 else {
31 if (urlPath.equals("/")) {// 設置rootHandler
32 if (logger.isInfoEnabled()) {
33 logger.info("Root mapping to " + getHandlerDescription(handler));
34 }
35 setRootHandler(resolvedHandler);
36 }
37 else if (urlPath.equals("/*")) {// 設置默認的defaultHandler
38 if (logger.isInfoEnabled()) {
39 logger.info("Default mapping to " + getHandlerDescription(handler));
40 }
41 setDefaultHandler(resolvedHandler);
42 }
43 else {// 最後纔是普通handler的設置
44 this.handlerMap.put(urlPath, resolvedHandler);
45 if (logger.isInfoEnabled()) {
46 logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler));
47 }
48 }
49 }
50 }