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本篇內容介紹了“springmvc path請求怎么映射到bean方法”的有關知識，在實際案例的操作過程中，不少人都會遇到這樣的困境，接下來就讓小編帶領大家學習一下如何處理這些情況吧！希望大家仔細閱讀，能夠學有所成！
1.在dispatch-servlet.xml中配置< mvc:annotation-driven/>，在控制器的方法上加入@RequestMapping注解即可。
2.mvc:annotation-driven的解析流程 會調用到自定義元素解析器的AnnotationDrivenBeanDefinitionParser.parse方法。
3.org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping為RequestMapping注解映射到后臺接口的注冊表。此類實現了InitializingBean接口，會觸發到
afterPropertiesSet方法。
org.springframework.web.servlet.handler.AbstractHandlerMethodMapping
@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());
}4.在initHandlerMethods方法中會先調用getCandidateBeanNames獲取當前容器工廠的所有BEAN,然后逐個BEAN進行處理。
4.1 獲取所有BEAN流程
protected String[] getCandidateBeanNames() {
return (this.detectHandlerMethodsInAncestorContexts ?
BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :
obtainApplicationContext().getBeanNamesForType(Object.class));
}4.2 處理BEAN流程
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);
}
}4.3 判斷當前BEAN是否HANDLER
protected boolean isHandler(Class<?> beanType) {
return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
}4.4 如果此類是控制器或者有requestMapping注解，才會處理。
4.5 遍歷當前類的所有方法，查找包含RequestMapping注解的方法，然后保存到
AbstractHandlerMethodMapping.MappingRegistry注冊表中。
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);
});
}
}判斷當前方法是否包含requestMapping注解
private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
RequestCondition<?> condition = (element instanceof Class ?
getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
}最終會調用org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.registerHandlerMethod保存到URL和RequestMappinfo的映射注冊表中。
AbstractHandlerMethodMapping
protected void registerHandlerMethod(Object handler, Method method, T mapping) {
this.mappingRegistry.register(mapping, handler, method);
}具體的保存邏輯
在這個方法中主要操作的數據對象有四個，分別是mappingLookup、urlLookup、corsLookup和registry。下面對這四個對象進行說明:
mappingLookup對象是Map結構，key表示mapping對象，value表示處理對象，在本例中key是RequestMappingInfo對象，value是Controller中的某一個方法。
urlLookup對象是Map結構，key表示url，value表示mapping對象，本例中key是具體的url值"/demo/postMapping/"，value是RequestMappingInfo對象，
corsLookup對象是Map結構，key表示處理方法（Controller中的某個方法），value表示跨域配置，本例中沒有進行跨域注解的使用因此數據不存在，如果需要看到跨域數據，可以在method上添加@CrossOrigin注解
registry對象是Map結構，key表示mapping對象，value表示MappingRegistration對象
AbstractHandlerMethodMapping.MappingRegistry 內部類
public void register(T mapping, Object handler, Method method) {
this.readWriteLock.writeLock().lock();
try {
HandlerMethod handlerMethod = createHandlerMethod(handler, method);
validateMethodMapping(handlerMethod, mapping);
this.mappingLookup.put(mapping, handlerMethod);
List<String> directUrls = getDirectUrls(mapping);
for (String url : directUrls) {
this.urlLookup.add(url, mapping);
}
String name = null;
if (getNamingStrategy() != null) {
name = getNamingStrategy().getName(handlerMethod, mapping);
addMappingName(name, handlerMethod);
}
this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
}
finally {
this.readWriteLock.writeLock().unlock();
}
}生成的數據如下：
5.系統攔截器列表初始化過程,會調用到AbstractHandlerMapping.initApplicationContext，這個會查找當前容器工廠中所有繼承了MappedInterceptor類的攔截器實例BEAN.然后保存到AbstractHandlerMapping.interceptors
protected void initApplicationContext() throws BeansException {
extendInterceptors(this.interceptors);
detectMappedInterceptors(this.adaptedInterceptors);
initInterceptors();
}
1.首先tomcat會調用DispatcherServlet.doDispatch方法，進行請求分發處理。
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());
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;
}
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
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);
}
}
}
}2.首先調用getHandler去根據請求PATH查找HandlerExecutionChain，HandlerExecutionChain就是一個RequestHandleMappinfo加上一個攔截器列表。會調用到AbstractHandlerMapping.getHandler
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
return executionChain;
}3.最終會調用到AbstractHandlerMapping.lookupHandlerMethod根據PATH查找HandlerMethod，這里面的 this.mappingRegistry.getMappingsByUrl就是初始化時的URL和RequestMappingInfo映射表。
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<>();
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
if (directPathMatches != null) {
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
if (!matches.isEmpty()) {
Match bestMatch = matches.get(0);
request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
handleMatch(bestMatch.mapping, lookupPath, request);
return bestMatch.handlerMethod;
}
else {
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
}調用堆棧1
調用堆棧2
4.
初始化HandlerExecutionChain攔截器列表，這個會查找當前容器工廠中所有實現了handleInteropr 的類，
AbstractHandlerMapping類
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request, LOOKUP_PATH);
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
這個類會根據攔截器的URL匹配規則相應添加攔截器列表。
<mvc:interceptors> <bean class="com.tpw.component.HandlerInterceptor1"></bean> <mvc:interceptor> <mvc:mapping path="/user"/> <bean class="com.tpw.component.HandlerInterceptor2"></bean> </mvc:interceptor> </mvc:interceptors>
5.調用所有攔截器的applyPreHandle方法
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(request, response, this.handler)) {
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
}7.然后調用invocableMethod.invokeAndHandle(webRequest, mavContainer)，首先通過反射調用handlerMethod中的bean的接口方法
ServletInvocableHandlerMethod
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
setResponseStatus(webRequest);
if (returnValue == null) {
if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
disableContentCachingIfNecessary(webRequest);
mavContainer.setRequestHandled(true);
return;
}
}
else if (StringUtils.hasText(getResponseStatusReason())) {
mavContainer.setRequestHandled(true);
return;
}
mavContainer.setRequestHandled(false);
Assert.state(this.returnValueHandlers != null, "No return value handlers");
try {
this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(formatErrorForReturnValue(returnValue), ex);
}
throw ex;
}
}
9.最后調用HandlerMethodReturnValueHandlerComposite.handleReturnValue 進行返回值處理，例如將BEAN轉JSON,轉XML等。
9.1 這個找HANDLER的過程也是，根據此HANDLER是否支持此方法，如在方法上加上了@ResponseBody,則會由RequestResponseBodyMethodProcessor處理。
RequestResponseBodyMethodProcessor
public boolean supportsReturnType(MethodParameter returnType) {
return (AnnotatedElementUtils.hasAnnotation(returnType.getContainingClass(), ResponseBody.class) ||
returnType.hasMethodAnnotation(ResponseBody.class));
}public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
HandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType);
if (handler == null) {
throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());
}
handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
}
RequestResponseBodyMethodProcessor。 此類繼承了AbstractMessageConverterMethodProcessor，這個類會調用當前容器工廠中所有
9.2 由于我們在方法上加了@ResponseBody注解，所有此handler為
protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType,
ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
Object body;
Class<?> valueType;
Type targetType;
if (value instanceof CharSequence) {
body = value.toString();
valueType = String.class;
targetType = String.class;
}
else {
body = value;
valueType = getReturnValueType(body, returnType);
targetType = GenericTypeResolver.resolveType(getGenericType(returnType), returnType.getContainingClass());
}
if (selectedMediaType != null) {
selectedMediaType = selectedMediaType.removeQualityValue();
for (HttpMessageConverter<?> converter : this.messageConverters) {
GenericHttpMessageConverter genericConverter = (converter instanceof GenericHttpMessageConverter ?
(GenericHttpMessageConverter<?>) converter : null);
if (genericConverter != null ?
((GenericHttpMessageConverter) converter).canWrite(targetType, valueType, selectedMediaType) :
converter.canWrite(valueType, selectedMediaType)) {
body = getAdvice().beforeBodyWrite(body, returnType, selectedMediaType,
(Class<? extends HttpMessageConverter<?>>) converter.getClass(),
inputMessage, outputMessage);
if (body != null) {
Object theBody = body;
LogFormatUtils.traceDebug(logger, traceOn ->
"Writing [" + LogFormatUtils.formatValue(theBody, !traceOn) + "]");
addContentDispositionHeader(inputMessage, outputMessage);
if (genericConverter != null) {
genericConverter.write(body, targetType, selectedMediaType, outputMessage);
}
else {
((HttpMessageConverter) converter).write(body, selectedMediaType, outputMessage);
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Nothing to write: null body");
}
}
return;
}
}
}
}
9.3 messageConverts的數據初始化來源為 RequestMappingHandlerAdapter.getDefaultArgumentResolvers方法中，
resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));
messageConverts來源于RequestMappingHandlerAdapter.messageConverters中。
在初始化時會，依賴注入當前系統中所有的messageConvert.
10.最后調用攔截器的所有postHandle方法進行，處理完回調。
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(request, response, this.handler, mv);
}
}
}11.在渲染完輸出視圖后，會調用所有攔截器的afterCompletion方法，注意，JSON,XML這種沒有視圖，只有HTML等才有。
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = this.interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
try {
interceptor.afterCompletion(request, response, this.handler, ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
}“springmvc path請求怎么映射到bean方法”的內容就介紹到這里了，感謝大家的閱讀。如果想了解更多行業相關的知識可以關注億速云網站，小編將為大家輸出更多高質量的實用文章！
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