简单读！spring-mvc源码之穿越http请求
2024-10-18 23:22:59
相信spring-mvc这种被玩坏了的架构理念，大家都烂熟于胸了，不过还是想来扒一扒他的细节。
一个http请求，怎么样被 spring 接收，又怎样做出响应呢？
一般地，我们会配置一个 web.xml，然后开始代码之旅。
在 web.xml 中配置 servlet-mapping, 将请求转发到 DispatcherServlet, 那么我们认为 DispatcherServlet 是我们的第一棒交接者！
<servlet>
<servlet-name>springMVC</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet> <servlet-mapping>
<servlet-name>springMVC</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
// tomcat 接到http请求后，会主动创建一个servlet, 然后调用进应用代码中, 创建的代码如下
// Allocate a servlet instance to process this request
try {
if (!unavailable) {
servlet = wrapper.allocate();
}
} catch (ServletException e) {
wrapper.getLogger().error(sm.getString("applicationDispatcher.allocateException",
wrapper.getName()), StandardWrapper.getRootCause(e));
servletException = e;
} catch (Throwable e) {
ExceptionUtils.handleThrowable(e);
wrapper.getLogger().error(sm.getString("applicationDispatcher.allocateException",
wrapper.getName()), e);
servletException = new ServletException
(sm.getString("applicationDispatcher.allocateException",
wrapper.getName()), e);
servlet = null;
}
// org.apache.catalina.core.StandardWrapper.allocate(), 创建 servlet,
/**
* Allocate an initialized instance of this Servlet that is ready to have
* its <code>service()</code> method called. If the servlet class does
* not implement <code>SingleThreadModel</code>, the (only) initialized
* instance may be returned immediately. If the servlet class implements
* <code>SingleThreadModel</code>, the Wrapper implementation must ensure
* that this instance is not allocated again until it is deallocated by a
* call to <code>deallocate()</code>.
*
* @exception ServletException if the servlet init() method threw
* an exception
* @exception ServletException if a loading error occurs
*/
@Override
public Servlet allocate() throws ServletException {
// If we are currently unloading this servlet, throw an exception
if (unloading) {
throw new ServletException(sm.getString("standardWrapper.unloading", getName()));
}
boolean newInstance = false;
// If not SingleThreadedModel, return the same instance every time
if (!singleThreadModel) {
// Load and initialize our instance if necessary
if (instance == null || !instanceInitialized) {
synchronized (this) {
if (instance == null) {
try {
if (log.isDebugEnabled()) {
log.debug("Allocating non-STM instance");
}
// Note: We don't know if the Servlet implements
// SingleThreadModel until we have loaded it.
instance = loadServlet();
newInstance = true;
if (!singleThreadModel) {
// For non-STM, increment here to prevent a race
// condition with unload. Bug 43683, test case
// #3
countAllocated.incrementAndGet();
}
} catch (ServletException e) {
throw e;
} catch (Throwable e) {
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("standardWrapper.allocate"), e);
}
}
if (!instanceInitialized) {
initServlet(instance);
}
}
}
if (singleThreadModel) {
if (newInstance) {
// Have to do this outside of the sync above to prevent a
// possible deadlock
synchronized (instancePool) {
instancePool.push(instance);
nInstances++;
}
}
} else {
if (log.isTraceEnabled()) {
log.trace(" Returning non-STM instance");
}
// For new instances, count will have been incremented at the
// time of creation
if (!newInstance) {
countAllocated.incrementAndGet();
}
return instance;
}
}
synchronized (instancePool) {
while (countAllocated.get() >= nInstances) {
// Allocate a new instance if possible, or else wait
if (nInstances < maxInstances) {
try {
instancePool.push(loadServlet());
nInstances++;
} catch (ServletException e) {
throw e;
} catch (Throwable e) {
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("standardWrapper.allocate"), e);
}
} else {
try {
instancePool.wait();
} catch (InterruptedException e) {
// Ignore
}
}
}
if (log.isTraceEnabled()) {
log.trace(" Returning allocated STM instance");
}
countAllocated.incrementAndGet();
return instancePool.pop();
}
}
// 最后，会先调用 filter, 完成之后再调用 servlet.service()
private void internalDoFilter(ServletRequest request,
ServletResponse response)
throws IOException, ServletException { // Call the next filter if there is one
if (pos < n) {
ApplicationFilterConfig filterConfig = filters[pos++];
try {
Filter filter = filterConfig.getFilter(); if (request.isAsyncSupported() && "false".equalsIgnoreCase(
filterConfig.getFilterDef().getAsyncSupported())) {
request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE);
}
if( Globals.IS_SECURITY_ENABLED ) {
final ServletRequest req = request;
final ServletResponse res = response;
Principal principal =
((HttpServletRequest) req).getUserPrincipal(); Object[] args = new Object[]{req, res, this};
SecurityUtil.doAsPrivilege ("doFilter", filter, classType, args, principal);
} else {
filter.doFilter(request, response, this);
}
} catch (IOException | ServletException | RuntimeException e) {
throw e;
} catch (Throwable e) {
e = ExceptionUtils.unwrapInvocationTargetException(e);
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("filterChain.filter"), e);
}
return;
} // We fell off the end of the chain -- call the servlet instance
try {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(request);
lastServicedResponse.set(response);
} if (request.isAsyncSupported() && !servletSupportsAsync) {
request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR,
Boolean.FALSE);
}
// Use potentially wrapped request from this point
if ((request instanceof HttpServletRequest) &&
(response instanceof HttpServletResponse) &&
Globals.IS_SECURITY_ENABLED ) {
final ServletRequest req = request;
final ServletResponse res = response;
Principal principal =
((HttpServletRequest) req).getUserPrincipal();
Object[] args = new Object[]{req, res};
SecurityUtil.doAsPrivilege("service",
servlet,
classTypeUsedInService,
args,
principal);
} else {
servlet.service(request, response);
}
} catch (IOException | ServletException | RuntimeException e) {
throw e;
} catch (Throwable e) {
e = ExceptionUtils.unwrapInvocationTargetException(e);
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("filterChain.servlet"), e);
} finally {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(null);
lastServicedResponse.set(null);
}
}
}
// 现在，到了 DispatcherServlet 出场了，由 DispatcherServlet 的父类 org.springframework.web.servlet.FrameworkServlet.service()接力， 开始处理
/**
* Override the parent class implementation in order to intercept PATCH requests.
*/
@Override
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { HttpMethod httpMethod = HttpMethod.resolve(request.getMethod());
if (HttpMethod.PATCH == httpMethod || httpMethod == null) {
processRequest(request, response);
}
else {
// 交由 HttpServlet.service() 处理，转发 doGet,doPost 等等方法
super.service(request, response);
}
} // 父类 HttpServlet.service(), 只负责转发请求，由子类进行相应处理
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
String method = req.getMethod(); if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
doGet(req, resp);
} else {
long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
if (ifModifiedSince < lastModified) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
} } else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp); } else if (method.equals(METHOD_POST)) {
doPost(req, resp); } else if (method.equals(METHOD_PUT)) {
doPut(req, resp); } else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp); } else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp); } else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp); } else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
// String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs); resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
// 比如 FrameworkServlet.doGet()/doXXX() 方法重写, 调用 processRequest()
/**
* Delegate GET requests to processRequest/doService.
* <p>Will also be invoked by HttpServlet's default implementation of {@code doHead},
* with a {@code NoBodyResponse} that just captures the content length.
* @see #doService
* @see #doHead
*/
@Override
protected final void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { processRequest(request, response);
}
// FrameworkServlet.processRequest() 做一些全局设置，然后交由 doService() 进行具体处理, doService() 由子类实现,也即 DispatcherServlet.doService()
protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { long startTime = System.currentTimeMillis();
Throwable failureCause = null; LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
LocaleContext localeContext = buildLocaleContext(request); RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes); WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor()); initContextHolders(request, localeContext, requestAttributes); try {
// 具体处理，交由 DispatcherServlet 处理
doService(request, response);
}
catch (ServletException ex) {
failureCause = ex;
throw ex;
}
catch (IOException ex) {
failureCause = ex;
throw ex;
}
catch (Throwable ex) {
failureCause = ex;
throw new NestedServletException("Request processing failed", ex);
} finally {
resetContextHolders(request, previousLocaleContext, previousAttributes);
if (requestAttributes != null) {
// 请求完成回调
requestAttributes.requestCompleted();
} if (logger.isDebugEnabled()) {
if (failureCause != null) {
this.logger.debug("Could not complete request", failureCause);
}
else {
if (asyncManager.isConcurrentHandlingStarted()) {
logger.debug("Leaving response open for concurrent processing");
}
else {
this.logger.debug("Successfully completed request");
}
}
} // 发布完成事件
publishRequestHandledEvent(request, response, startTime, failureCause);
}
}
// locale 上下文管理
private void initContextHolders(
HttpServletRequest request, LocaleContext localeContext, RequestAttributes requestAttributes) { // private static final ThreadLocal<LocaleContext> localeContextHolder = new NamedThreadLocal<LocaleContext>("LocaleContext");
if (localeContext != null) {
LocaleContextHolder.setLocaleContext(localeContext, this.threadContextInheritable);
}
// private static final ThreadLocal<RequestAttributes> requestAttributesHolder = new NamedThreadLocal<RequestAttributes>("Request attributes");
if (requestAttributes != null) {
RequestContextHolder.setRequestAttributes(requestAttributes, this.threadContextInheritable);
}
if (logger.isTraceEnabled()) {
logger.trace("Bound request context to thread: " + request);
}
}
// org.springframework.web.servlet.DispatcherServlet, 进行具体请求转发
/**
* 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 {
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<String, Object>();
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.
// 设备各种处理器到 request 中
// 上下文管理
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
// locale 管理
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
// themeResolver
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); 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);
}
}
}
}
// doDispatch(), 实际分发方法
/**
* 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 {
// 封装 multipart 文件上传，如果是文件上传类，则将其封装为 MultipartHttpServletRequest, 以便后续直接使用
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request); // 获取具体uri业务处理器,即 由 RequestMapping 设置的路径
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
// 如果没有找到 handler 则结束处理
noHandlerFound(processedRequest, response);
return;
} // Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // 对GET|HEAD 进行 last-modified 进行检测
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;
}
} // 进行处理器前置调用，如果未通过，则结束
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
} // Actually invoke the handler.
// 调用业务处理
mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) {
return;
} // 设置 view
applyDefaultViewName(processedRequest, mv);
// 后置处理
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);
}
// 最后再处理一次结果，如果有必要的话
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 {
// 清理环境
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);
}
}
}
}
// multipart 检测，需设置 multipartResolver, 方能转换，否则直接返回原始请求
/**
* Convert the request into a multipart request, and make multipart resolver available.
* <p>If no multipart resolver is set, simply use the existing request.
* @param request current HTTP request
* @return the processed request (multipart wrapper if necessary)
* @see MultipartResolver#resolveMultipart
*/
protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException {
if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) {
if (WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class) != null) {
logger.debug("Request is already a MultipartHttpServletRequest - if not in a forward, " +
"this typically results from an additional MultipartFilter in web.xml");
}
else if (hasMultipartException(request) ) {
logger.debug("Multipart resolution failed for current request before - " +
"skipping re-resolution for undisturbed error rendering");
}
else {
try {
// 调用 multipartResolver.resolveMultipart(), 由 resolver 进行文件转换处理
return this.multipartResolver.resolveMultipart(request);
}
catch (MultipartException ex) {
if (request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) != null) {
logger.debug("Multipart resolution failed for error dispatch", ex);
// Keep processing error dispatch with regular request handle below
}
else {
throw ex;
}
}
}
}
// If not returned before: return original request.
return request;
}
// 关键: 获取handler, 以待调用
/**
* Return the HandlerExecutionChain for this request.
* <p>Tries all handler mappings in order.
* @param request current HTTP request
* @return the HandlerExecutionChain, or {@code null} if no handler could be found
*/
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
// handlerMappings 中保存了所有可用的路由
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
// 由具体的 HandlerMapping 去解析自己的映射
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
return null;
} // org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping
// org.springframework.web.servlet.handler.AbstractHandlerMapping.getHandler()
/**
* Look up a handler for the given request, falling back to the default
* handler if no specific one is found.
* @param request current HTTP request
* @return the corresponding handler instance, or the default handler
* @see #getHandlerInternal
*/
@Override
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
// 获取 handlerMethod
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 = getApplicationContext().getBean(handlerName);
} // 获取 handler 链
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
} // org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(), 查找 handler
/**
* Look up a handler method for the given request.
*/
@Override
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
// UrlHelper.getLookupPathForRequest() 进行路径分析
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
if (logger.isDebugEnabled()) {
logger.debug("Looking up handler method for path " + lookupPath);
}
// 加锁读取
this.mappingRegistry.acquireReadLock();
try {
// 根据path查找 handlerMethod
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
if (logger.isDebugEnabled()) {
if (handlerMethod != null) {
logger.debug("Returning handler method [" + handlerMethod + "]");
}
else {
logger.debug("Did not find handler method for [" + lookupPath + "]");
}
}
// 找到匹配后，将 handler 通过 bean 查找方式包装进 HandlerMethod 中返回
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
this.mappingRegistry.releaseReadLock();
}
}
// 更细节的查询 handler 动作
// org.springframework.web.util.UrlPathHelper
/**
* Return the mapping lookup path for the given request, within the current
* servlet mapping if applicable, else within the web application.
* <p>Detects include request URL if called within a RequestDispatcher include.
* @param request current HTTP request
* @return the lookup path
* @see #getPathWithinApplication
* @see #getPathWithinServletMapping
*/
public String getLookupPathForRequest(HttpServletRequest request) {
// Always use full path within current servlet context?
if (this.alwaysUseFullPath) {
return getPathWithinApplication(request);
}
// Else, use path within current servlet mapping if applicable
String rest = getPathWithinServletMapping(request);
if (!"".equals(rest)) {
return rest;
}
else {
// 返回 /hello/test
return getPathWithinApplication(request);
}
} //
/**
* Return the path within the servlet mapping for the given request,
* i.e. the part of the request's URL beyond the part that called the servlet,
* or "" if the whole URL has been used to identify the servlet.
* <p>Detects include request URL if called within a RequestDispatcher include.
* <p>E.g.: servlet mapping = "/*"; request URI = "/test/a" -> "/test/a".
* <p>E.g.: servlet mapping = "/"; request URI = "/test/a" -> "/test/a".
* <p>E.g.: servlet mapping = "/test/*"; request URI = "/test/a" -> "/a".
* <p>E.g.: servlet mapping = "/test"; request URI = "/test" -> "".
* <p>E.g.: servlet mapping = "/*.test"; request URI = "/a.test" -> "".
* @param request current HTTP request
* @return the path within the servlet mapping, or ""
*/
public String getPathWithinServletMapping(HttpServletRequest request) {
String pathWithinApp = getPathWithinApplication(request);
String servletPath = getServletPath(request);
String sanitizedPathWithinApp = getSanitizedPath(pathWithinApp);
String path; // If the app container sanitized the servletPath, check against the sanitized version
if (servletPath.contains(sanitizedPathWithinApp)) {
path = getRemainingPath(sanitizedPathWithinApp, servletPath, false);
}
else {
path = getRemainingPath(pathWithinApp, servletPath, false);
} if (path != null) {
// Normal case: URI contains servlet path.
return path;
}
else {
// Special case: URI is different from servlet path.
String pathInfo = request.getPathInfo();
if (pathInfo != null) {
// Use path info if available. Indicates index page within a servlet mapping?
// e.g. with index page: URI="/", servletPath="/index.html"
return pathInfo;
}
if (!this.urlDecode) {
// No path info... (not mapped by prefix, nor by extension, nor "/*")
// For the default servlet mapping (i.e. "/"), urlDecode=false can
// cause issues since getServletPath() returns a decoded path.
// If decoding pathWithinApp yields a match just use pathWithinApp.
path = getRemainingPath(decodeInternal(request, pathWithinApp), servletPath, false);
if (path != null) {
return pathWithinApp;
}
}
// Otherwise, use the full servlet path.
return servletPath;
}
} // org.springframework.web.servlet.handler.AbstractHandlerMethodMapping
/**
* Look up the best-matching handler method for the current request.
* If multiple matches are found, the best match is selected.
* @param lookupPath mapping lookup path within the current servlet mapping
* @param request the current request
* @return the best-matching handler method, or {@code null} if no match
* @see #handleMatch(Object, String, HttpServletRequest)
* @see #handleNoMatch(Set, String, HttpServletRequest)
*/
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<Match>();
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
if (directPathMatches != null) {
// 添加到匹配中，考虑不止一个匹配
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()) {
// 如果有多个匹配，进行优先级排序，判断是否可用，然后取第一个作为最终的 handler
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
Collections.sort(matches, comparator);
if (logger.isTraceEnabled()) {
logger.trace("Found " + matches.size() + " matching mapping(s) for [" +
lookupPath + "] : " + matches);
}
Match bestMatch = matches.get(0);
if (matches.size() > 1) {
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
Match secondBestMatch = matches.get(1);
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" +
request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
}
}
// 解析参数到 handlerMethod 中
handleMatch(bestMatch.mapping, lookupPath, request);
return bestMatch.handlerMethod;
}
else {
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
} // AbstractHandlerMethodMapping$MappingRegistry.getMappingsByUrl()
/**
* Return matches for the given URL path. Not thread-safe.
* @see #acquireReadLock()
*/
public List<T> getMappingsByUrl(String urlPath) {
// private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<String, T>();
// 内部使用 Map<K, List<V>> targetMap; 进行保存关系映射
return this.urlLookup.get(urlPath);
} // AbstractHandlerMethodMapping, 将确实有效的mapping添加到 matches 中
private void addMatchingMappings(Collection<T> mappings, List<Match> matches, HttpServletRequest request) {
for (T mapping : mappings) {
// 重新严格校验路径，参数，header， 返回新的mapping
T match = getMatchingMapping(mapping, request);
if (match != null) {
// 将 handler 放入 match
// private class Match {}
matches.add(new Match(match, this.mappingRegistry.getMappings().get(mapping)));
}
}
}
// org.springframework.web.servlet.mvc.condition.HeadersRequestCondition
// org.springframework.web.servlet.mvc.method.RequestMappingInfo
// 进行参数校验，并封装返回参数信息到 RequestMappingInfo 中返回
/**
* Checks if all conditions in this request mapping info match the provided request and returns
* a potentially new request mapping info with conditions tailored to the current request.
* <p>For example the returned instance may contain the subset of URL patterns that match to
* the current request, sorted with best matching patterns on top.
* @return a new instance in case all conditions match; or {@code null} otherwise
*/
@Override
public RequestMappingInfo getMatchingCondition(HttpServletRequest request) {
RequestMethodsRequestCondition methods = this.methodsCondition.getMatchingCondition(request);
ParamsRequestCondition params = this.paramsCondition.getMatchingCondition(request);
HeadersRequestCondition headers = this.headersCondition.getMatchingCondition(request);
ConsumesRequestCondition consumes = this.consumesCondition.getMatchingCondition(request);
ProducesRequestCondition produces = this.producesCondition.getMatchingCondition(request); // 其中某个不匹配，则返回 null
if (methods == null || params == null || headers == null || consumes == null || produces == null) {
return null;
} PatternsRequestCondition patterns = this.patternsCondition.getMatchingCondition(request);
if (patterns == null) {
return null;
} RequestConditionHolder custom = this.customConditionHolder.getMatchingCondition(request);
if (custom == null) {
return null;
} return new RequestMappingInfo(this.name, patterns,
methods, params, headers, consumes, produces, custom.getCondition());
}
/**
* Expose URI template variables, matrix variables, and producible media types in the request.
* @see HandlerMapping#URI_TEMPLATE_VARIABLES_ATTRIBUTE
* @see HandlerMapping#MATRIX_VARIABLES_ATTRIBUTE
* @see HandlerMapping#PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE
*/
@Override
protected void handleMatch(RequestMappingInfo info, String lookupPath, HttpServletRequest request) {
super.handleMatch(info, lookupPath, request); String bestPattern;
Map<String, String> uriVariables;
Map<String, String> decodedUriVariables; Set<String> patterns = info.getPatternsCondition().getPatterns();
if (patterns.isEmpty()) {
bestPattern = lookupPath;
uriVariables = Collections.emptyMap();
decodedUriVariables = Collections.emptyMap();
}
else {
bestPattern = patterns.iterator().next();
uriVariables = getPathMatcher().extractUriTemplateVariables(bestPattern, lookupPath);
decodedUriVariables = getUrlPathHelper().decodePathVariables(request, uriVariables);
} request.setAttribute(BEST_MATCHING_PATTERN_ATTRIBUTE, bestPattern);
request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, decodedUriVariables); if (isMatrixVariableContentAvailable()) {
Map<String, MultiValueMap<String, String>> matrixVars = extractMatrixVariables(request, uriVariables);
request.setAttribute(HandlerMapping.MATRIX_VARIABLES_ATTRIBUTE, matrixVars);
} if (!info.getProducesCondition().getProducibleMediaTypes().isEmpty()) {
Set<MediaType> mediaTypes = info.getProducesCondition().getProducibleMediaTypes();
request.setAttribute(PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, mediaTypes);
}
}
// org.springframework.web.method.HandlerMethod.createWithResolvedBean(), 重新包装一个带bean实例的 HandlerMethod
/**
* If the provided instance contains a bean name rather than an object instance,
* the bean name is resolved before a {@link HandlerMethod} is created and returned.
*/
public HandlerMethod createWithResolvedBean() {
Object handler = this.bean;
if (this.bean instanceof String) {
String beanName = (String) this.bean;
// spring beans 组件
handler = this.beanFactory.getBean(beanName);
}
return new HandlerMethod(this, handler);
}
/**
* Build a {@link HandlerExecutionChain} for the given handler, including
* applicable interceptors.
* <p>The default implementation builds a standard {@link HandlerExecutionChain}
* with the given handler, the handler mapping's common interceptors, and any
* {@link MappedInterceptor}s matching to the current request URL. Interceptors
* are added in the order they were registered. Subclasses may override this
* in order to extend/rearrange the list of interceptors.
* <p><b>NOTE:</b> The passed-in handler object may be a raw handler or a
* pre-built {@link HandlerExecutionChain}. This method should handle those
* two cases explicitly, either building a new {@link HandlerExecutionChain}
* or extending the existing chain.
* <p>For simply adding an interceptor in a custom subclass, consider calling
* {@code super.getHandlerExecutionChain(handler, request)} and invoking
* {@link HandlerExecutionChain#addInterceptor} on the returned chain object.
* @param handler the resolved handler instance (never {@code null})
* @param request current HTTP request
* @return the HandlerExecutionChain (never {@code null})
* @see #getAdaptedInterceptors()
*/
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
// 取出内层的 interceptor 使用
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
// 获取 adapter，适配不同类型的调用
// org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter
// org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter
// org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter
/**
* Return the HandlerAdapter for this handler object.
* @param handler the handler object to find an adapter for
* @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.
*/
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
for (HandlerAdapter ha : this.handlerAdapters) {
if (logger.isTraceEnabled()) {
logger.trace("Testing handler adapter [" + ha + "]");
}
if (ha.supports(handler)) {
return ha;
}
}
throw new ServletException("No adapter for handler [" + handler +
"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
}
// mappedHandler.applyPreHandle(processedRequest, response) , 前置调用处理, interceptor 拦截调用
/**
* Apply preHandle methods of registered interceptors.
* @return {@code true} if the execution chain should proceed with the
* next interceptor or the handler itself. Else, DispatcherServlet assumes
* that this interceptor has already dealt with the response itself.
*/
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];
// 接收 preHandle 返回值, false 则终止
if (!interceptor.preHandle(request, response, this.handler)) {
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
}
// mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); 真正调用 handler 处理业务
// org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter
// method.AbstractHandlerMethodAdapter
/**
* This implementation expects the handler to be an {@link HandlerMethod}.
*/
@Override
public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
// 内部调用
return handleInternal(request, response, (HandlerMethod) handler);
} //
@Override
protected ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ModelAndView mav;
// 预检查是否可支持
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...
// invoke
mav = invokeHandlerMethod(request, response, handlerMethod);
} if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
}
else {
prepareResponse(response);
}
} return mav;
}
//org.springframework.web.servlet.support.WebContentGenerator.checkRequest()
/**
* Check the given request for supported methods and a required session, if any.
* @param request current HTTP request
* @throws ServletException if the request cannot be handled because a check failed
* @since 4.2
*/
protected final void checkRequest(HttpServletRequest request) throws ServletException {
// Check whether we should support the request method.
String method = request.getMethod();
if (this.supportedMethods != null && !this.supportedMethods.contains(method)) {
throw new HttpRequestMethodNotSupportedException(method, this.supportedMethods);
} // Check whether a session is required.
if (this.requireSession && request.getSession(false) == null) {
throw new HttpSessionRequiredException("Pre-existing session required but none found");
}
}
// 调用 Adapter 的 handler 处理方法
/**
* Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView}
* if view resolution is required.
* @since 4.2
* @see #createInvocableHandlerMethod(HandlerMethod)
*/
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ServletWebRequest webRequest = new ServletWebRequest(request, response);
try {
// 获取参数绑定工厂
WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
// 参数解析
ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory); // createInvocableHandlerMethod, 反射调用工具类
ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
invocableMethod.setDataBinderFactory(binderFactory);
invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer); // mav
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
modelFactory.initModel(webRequest, mavContainer, invocableMethod);
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect); AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
asyncWebRequest.setTimeout(this.asyncRequestTimeout); WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.setTaskExecutor(this.taskExecutor);
asyncManager.setAsyncWebRequest(asyncWebRequest);
asyncManager.registerCallableInterceptors(this.callableInterceptors);
asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors); if (asyncManager.hasConcurrentResult()) {
Object result = asyncManager.getConcurrentResult();
mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
asyncManager.clearConcurrentResult();
if (logger.isDebugEnabled()) {
logger.debug("Found concurrent result value [" + result + "]");
}
invocableMethod = invocableMethod.wrapConcurrentResult(result);
} // 调用业务 controller
invocableMethod.invokeAndHandle(webRequest, mavContainer);
if (asyncManager.isConcurrentHandlingStarted()) {
return null;
} // 返回 mv, jsp, 如果是 json 一类的输出，则直接返回 null
return getModelAndView(mavContainer, modelFactory, webRequest);
}
finally {
webRequest.requestCompleted();
}
}
细节点的工厂类创建：
// 参数绑定工厂
private WebDataBinderFactory getDataBinderFactory(HandlerMethod handlerMethod) throws Exception {
Class<?> handlerType = handlerMethod.getBeanType();
Set<Method> methods = this.initBinderCache.get(handlerType);
if (methods == null) {
methods = MethodIntrospector.selectMethods(handlerType, INIT_BINDER_METHODS);
this.initBinderCache.put(handlerType, methods);
}
List<InvocableHandlerMethod> initBinderMethods = new ArrayList<InvocableHandlerMethod>();
// Global methods first
for (Entry<ControllerAdviceBean, Set<Method>> entry : this.initBinderAdviceCache.entrySet()) {
if (entry.getKey().isApplicableToBeanType(handlerType)) {
Object bean = entry.getKey().resolveBean();
for (Method method : entry.getValue()) {
initBinderMethods.add(createInitBinderMethod(bean, method));
}
}
}
for (Method method : methods) {
Object bean = handlerMethod.getBean();
initBinderMethods.add(createInitBinderMethod(bean, method));
}
return createDataBinderFactory(initBinderMethods);
} // 参数解析工厂
private ModelFactory getModelFactory(HandlerMethod handlerMethod, WebDataBinderFactory binderFactory) {
SessionAttributesHandler sessionAttrHandler = getSessionAttributesHandler(handlerMethod);
Class<?> handlerType = handlerMethod.getBeanType();
Set<Method> methods = this.modelAttributeCache.get(handlerType);
if (methods == null) {
methods = MethodIntrospector.selectMethods(handlerType, MODEL_ATTRIBUTE_METHODS);
this.modelAttributeCache.put(handlerType, methods);
}
List<InvocableHandlerMethod> attrMethods = new ArrayList<InvocableHandlerMethod>();
// Global methods first
for (Entry<ControllerAdviceBean, Set<Method>> entry : this.modelAttributeAdviceCache.entrySet()) {
if (entry.getKey().isApplicableToBeanType(handlerType)) {
Object bean = entry.getKey().resolveBean();
for (Method method : entry.getValue()) {
attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
}
}
}
for (Method method : methods) {
Object bean = handlerMethod.getBean();
attrMethods.add(createModelAttributeMethod(binderFactory, bean, method));
}
return new ModelFactory(attrMethods, binderFactory, sessionAttrHandler);
}
// org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle()
/**
* Invoke the method and handle the return value through one of the
* configured {@link HandlerMethodReturnValueHandler}s.
* @param webRequest the current request
* @param mavContainer the ModelAndViewContainer for this request
* @param providedArgs "given" arguments matched by type (not resolved)
*/
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception { // 直接调用 handler
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
// 设置响应码
setResponseStatus(webRequest); if (returnValue == null) {
if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
mavContainer.setRequestHandled(true);
return;
}
}
else if (StringUtils.hasText(getResponseStatusReason())) {
mavContainer.setRequestHandled(true);
return;
} mavContainer.setRequestHandled(false);
try {
// 处理返回值
this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(getReturnValueHandlingErrorMessage("Error handling return value", returnValue), ex);
}
throw ex;
}
} // InvocableHandlerMethod.invokeForRequest()
/**
* Invoke the method after resolving its argument values in the context of the given request.
* <p>Argument values are commonly resolved through {@link HandlerMethodArgumentResolver}s.
* The {@code providedArgs} parameter however may supply argument values to be used directly,
* i.e. without argument resolution. Examples of provided argument values include a
* {@link WebDataBinder}, a {@link SessionStatus}, or a thrown exception instance.
* Provided argument values are checked before argument resolvers.
* @param request the current request
* @param mavContainer the ModelAndViewContainer for this request
* @param providedArgs "given" arguments matched by type, not resolved
* @return the raw value returned by the invoked method
* @exception Exception raised if no suitable argument resolver can be found,
* or if the method raised an exception
*/
public Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception { // 获取方法参数
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
if (logger.isTraceEnabled()) {
logger.trace("Invoking '" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +
"' with arguments " + Arrays.toString(args));
}
// invoke
Object returnValue = doInvoke(args);
if (logger.isTraceEnabled()) {
logger.trace("Method [" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +
"] returned [" + returnValue + "]");
}
return returnValue;
}
// 参数封装，InvocableHandlerMethod.getMethodArgumentValues()
// InvocableHandlerMethod.getMethodArgumentValues()
/**
* Get the method argument values for the current request.
*/
private Object[] getMethodArgumentValues(NativeWebRequest request, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception { MethodParameter[] parameters = getMethodParameters();
Object[] args = new Object[parameters.length];
for (int i = 0; i < parameters.length; i++) {
MethodParameter parameter = parameters[i];
parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
args[i] = resolveProvidedArgument(parameter, providedArgs);
if (args[i] != null) {
continue;
}
if (this.argumentResolvers.supportsParameter(parameter)) {
try {
args[i] = this.argumentResolvers.resolveArgument(
parameter, mavContainer, request, this.dataBinderFactory);
continue;
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug(getArgumentResolutionErrorMessage("Failed to resolve", i), ex);
}
throw ex;
}
}
if (args[i] == null) {
throw new IllegalStateException("Could not resolve method parameter at index " +
parameter.getParameterIndex() + " in " + parameter.getMethod().toGenericString() +
": " + getArgumentResolutionErrorMessage("No suitable resolver for", i));
}
}
return args;
} // org.springframework.web.method.support.HandlerMethodArgumentResolverComposite
/**
* Iterate over registered {@link HandlerMethodArgumentResolver}s and invoke the one that supports it.
* @throws IllegalStateException if no suitable {@link HandlerMethodArgumentResolver} is found.
*/
@Override
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
if (resolver == null) {
throw new IllegalArgumentException("Unknown parameter type [" + parameter.getParameterType().getName() + "]");
}
return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
} // AbstractNamedValueMethodArgumentResolver @Override
public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
MethodParameter nestedParameter = parameter.nestedIfOptional(); // 处理 key
Object resolvedName = resolveStringValue(namedValueInfo.name);
if (resolvedName == null) {
throw new IllegalArgumentException(
"Specified name must not resolve to null: [" + namedValueInfo.name + "]");
} // 获取 value
Object arg = resolveName(resolvedName.toString(), nestedParameter, webRequest);
if (arg == null) {
if (namedValueInfo.defaultValue != null) {
arg = resolveStringValue(namedValueInfo.defaultValue);
}
else if (namedValueInfo.required && !nestedParameter.isOptional()) {
handleMissingValue(namedValueInfo.name, nestedParameter, webRequest);
}
arg = handleNullValue(namedValueInfo.name, arg, nestedParameter.getNestedParameterType());
}
else if ("".equals(arg) && namedValueInfo.defaultValue != null) {
arg = resolveStringValue(namedValueInfo.defaultValue);
} if (binderFactory != null) {
WebDataBinder binder = binderFactory.createBinder(webRequest, null, namedValueInfo.name);
try {
arg = binder.convertIfNecessary(arg, parameter.getParameterType(), parameter);
}
catch (ConversionNotSupportedException ex) {
throw new MethodArgumentConversionNotSupportedException(arg, ex.getRequiredType(),
namedValueInfo.name, parameter, ex.getCause());
}
catch (TypeMismatchException ex) {
throw new MethodArgumentTypeMismatchException(arg, ex.getRequiredType(),
namedValueInfo.name, parameter, ex.getCause()); }
} handleResolvedValue(arg, namedValueInfo.name, parameter, mavContainer, webRequest); return arg;
}
// Object returnValue = doInvoke(args);
// InvocableHandlerMethod.doInvoke(), 正常返回结果，异常包装返回
/**
* Invoke the handler method with the given argument values.
*/
protected Object doInvoke(Object... args) throws Exception {
// 确保方法可调用
ReflectionUtils.makeAccessible(getBridgedMethod());
try {
// 调用业务方法
return getBridgedMethod().invoke(getBean(), args);
}
catch (IllegalArgumentException ex) {
assertTargetBean(getBridgedMethod(), getBean(), args);
String text = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument");
throw new IllegalStateException(getInvocationErrorMessage(text, args), ex);
}
catch (InvocationTargetException ex) {
// Unwrap for HandlerExceptionResolvers ...
Throwable targetException = ex.getTargetException();
if (targetException instanceof RuntimeException) {
throw (RuntimeException) targetException;
}
else if (targetException instanceof Error) {
throw (Error) targetException;
}
else if (targetException instanceof Exception) {
throw (Exception) targetException;
}
else {
String text = getInvocationErrorMessage("Failed to invoke handler method", args);
throw new IllegalStateException(text, targetException);
}
}
}
// 至此业务方法终于调用完成
// 接下来，处理返回值
// this.returnValueHandlers.handleReturnValue(
// returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
// org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue()
/**
* Iterate over registered {@link HandlerMethodReturnValueHandler}s and invoke the one that supports it.
* @throws IllegalStateException if no suitable {@link HandlerMethodReturnValueHandler} is found.
*/
@Override
public void handleReturnValue(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);
} // 返回值处理器
// org.springframework.web.servlet.mvc.method.annotation.ModelAndViewMethodReturnValueHandler
// org.springframework.web.method.annotation.ModelMethodProcessor
// org.springframework.web.servlet.mvc.method.annotation.ViewMethodReturnValueHandler
// org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler
// org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBodyReturnValueHandler
// org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor
// org.springframework.web.servlet.mvc.method.annotation.HttpHeadersReturnValueHandler
// org.springframework.web.servlet.mvc.method.annotation.CallableMethodReturnValueHandler
// org.springframework.web.servlet.mvc.method.annotation.DeferredResultMethodReturnValueHandler
// org.springframework.web.servlet.mvc.method.annotation.AsyncTaskMethodReturnValueHandler
// org.springframework.web.method.annotation.ModelAttributeMethodProcessor
// org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor
// org.springframework.web.servlet.mvc.method.annotation.ViewNameMethodReturnValueHandler
// org.springframework.web.method.annotation.MapMethodProcessor
// org.springframework.web.method.annotation.ModelAttributeMethodProcessor
private HandlerMethodReturnValueHandler selectHandler(Object value, MethodParameter returnType) {
boolean isAsyncValue = isAsyncReturnValue(value, returnType);
for (HandlerMethodReturnValueHandler handler : this.returnValueHandlers) {
if (isAsyncValue && !(handler instanceof AsyncHandlerMethodReturnValueHandler)) {
continue;
}
// return Callable.class.isAssignableFrom(returnType.getParameterType());
// return (AnnotatedElementUtils.hasAnnotation(returnType.getContainingClass(), ResponseBody.class) ||
// returnType.hasMethodAnnotation(ResponseBody.class));
if (handler.supportsReturnType(returnType)) {
return handler;
}
}
return null;
} // org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(), 处理返回结果
@Override
public void handleReturnValue(Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException { mavContainer.setRequestHandled(true);
ServletServerHttpRequest inputMessage = createInputMessage(webRequest);
ServletServerHttpResponse outputMessage = createOutputMessage(webRequest); // 写返回值
// Try even with null return value. ResponseBodyAdvice could get involved.
writeWithMessageConverters(returnValue, returnType, inputMessage, outputMessage);
} /**
* Creates a new {@link HttpOutputMessage} from the given {@link NativeWebRequest}.
* @param webRequest the web request to create an output message from
* @return the output message
*/
protected ServletServerHttpResponse createOutputMessage(NativeWebRequest webRequest) {
HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
return new ServletServerHttpResponse(response);
} /**
* Writes the given return type to the given output message.
* @param value the value to write to the output message
* @param returnType the type of the value
* @param inputMessage the input messages. Used to inspect the {@code Accept} header.
* @param outputMessage the output message to write to
* @throws IOException thrown in case of I/O errors
* @throws HttpMediaTypeNotAcceptableException thrown when the conditions indicated
* by the {@code Accept} header on the request cannot be met by the message converters
*/
@SuppressWarnings("unchecked")
protected <T> void writeWithMessageConverters(T value, MethodParameter returnType,
ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException { Object outputValue;
Class<?> valueType;
Type declaredType; if (value instanceof CharSequence) {
// string 的返回值输出
outputValue = value.toString();
valueType = String.class;
declaredType = String.class;
}
else {
outputValue = value;
valueType = getReturnValueType(outputValue, returnType);
declaredType = getGenericType(returnType);
} HttpServletRequest request = inputMessage.getServletRequest();
// 获取返回的 content-type 值
List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request);
List<MediaType> producibleMediaTypes = getProducibleMediaTypes(request, valueType, declaredType); if (outputValue != null && producibleMediaTypes.isEmpty()) {
throw new IllegalArgumentException("No converter found for return value of type: " + valueType);
} Set<MediaType> compatibleMediaTypes = new LinkedHashSet<MediaType>();
for (MediaType requestedType : requestedMediaTypes) {
for (MediaType producibleType : producibleMediaTypes) {
if (requestedType.isCompatibleWith(producibleType)) {
compatibleMediaTypes.add(getMostSpecificMediaType(requestedType, producibleType));
}
}
}
if (compatibleMediaTypes.isEmpty()) {
if (outputValue != null) {
throw new HttpMediaTypeNotAcceptableException(producibleMediaTypes);
}
return;
} List<MediaType> mediaTypes = new ArrayList<MediaType>(compatibleMediaTypes);
MediaType.sortBySpecificityAndQuality(mediaTypes); // 确定输出的类型
MediaType selectedMediaType = null;
for (MediaType mediaType : mediaTypes) {
if (mediaType.isConcrete()) {
selectedMediaType = mediaType;
break;
}
else if (mediaType.equals(MediaType.ALL) || mediaType.equals(MEDIA_TYPE_APPLICATION)) {
selectedMediaType = MediaType.APPLICATION_OCTET_STREAM;
break;
}
} if (selectedMediaType != null) {
selectedMediaType = selectedMediaType.removeQualityValue();
// 使用 messageConverter 进行返回值转换
// org.springframework.http.converter.ByteArrayHttpMessageConverter
// org.springframework.http.converter.StringHttpMessageConverter
// org.springframework.http.converter.ResourceHttpMessageConverter
// org.springframework.http.converter.xml.SourceHttpMessageConverter
// org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter
// org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter
// org.springframework.http.converter.ByteArrayHttpMessageConverter
// org.springframework.http.converter.StringHttpMessageConverter
// org.springframework.http.converter.ResourceHttpMessageConverter
// org.springframework.http.converter.xml.SourceHttpMessageConverter
// org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter
// org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter
for (HttpMessageConverter<?> messageConverter : this.messageConverters) {
if (messageConverter instanceof GenericHttpMessageConverter) {
if (((GenericHttpMessageConverter) messageConverter).canWrite(
declaredType, valueType, selectedMediaType)) {
outputValue = (T) getAdvice().beforeBodyWrite(outputValue, returnType, selectedMediaType,
(Class<? extends HttpMessageConverter<?>>) messageConverter.getClass(),
inputMessage, outputMessage);
if (outputValue != null) {
addContentDispositionHeader(inputMessage, outputMessage);
((GenericHttpMessageConverter) messageConverter).write(
outputValue, declaredType, selectedMediaType, outputMessage);
if (logger.isDebugEnabled()) {
logger.debug("Written [" + outputValue + "] as \"" + selectedMediaType +
"\" using [" + messageConverter + "]");
}
}
return;
}
}
else if (messageConverter.canWrite(valueType, selectedMediaType)) {
// 输出值
outputValue = (T) getAdvice().beforeBodyWrite(outputValue, returnType, selectedMediaType,
(Class<? extends HttpMessageConverter<?>>) messageConverter.getClass(),
inputMessage, outputMessage);
if (outputValue != null) {
addContentDispositionHeader(inputMessage, outputMessage);
// write
((HttpMessageConverter) messageConverter).write(outputValue, selectedMediaType, outputMessage);
if (logger.isDebugEnabled()) {
logger.debug("Written [" + outputValue + "] as \"" + selectedMediaType +
"\" using [" + messageConverter + "]");
}
}
return;
}
}
} if (outputValue != null) {
throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes);
}
}
// 消息转换器
// org.springframework.http.converter.StringHttpMessageConverter
// org.springframework.http.converter.AbstractHttpMessageConverter
// org.springframework.http.converter.StringHttpMessageConverter
// org.springframework.http.converter.AbstractHttpMessageConverter
/**
* This implementation sets the default headers by calling {@link #addDefaultHeaders},
* and then calls {@link #writeInternal}.
*/
@Override
public final void write(final T t, MediaType contentType, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException { final HttpHeaders headers = outputMessage.getHeaders();
addDefaultHeaders(headers, t, contentType); if (outputMessage instanceof StreamingHttpOutputMessage) {
StreamingHttpOutputMessage streamingOutputMessage =
(StreamingHttpOutputMessage) outputMessage;
streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
@Override
public void writeTo(final OutputStream outputStream) throws IOException {
writeInternal(t, new HttpOutputMessage() {
@Override
public OutputStream getBody() throws IOException {
return outputStream;
}
@Override
public HttpHeaders getHeaders() {
return headers;
}
});
}
});
}
else {
// write
writeInternal(t, outputMessage);
// 再次 flush()
outputMessage.getBody().flush();
}
} // StringHttpMessageConverter
@Override
protected void writeInternal(String str, HttpOutputMessage outputMessage) throws IOException {
if (this.writeAcceptCharset) {
outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets());
}
Charset charset = getContentTypeCharset(outputMessage.getHeaders().getContentType());
StreamUtils.copy(str, charset, outputMessage.getBody());
} // org.springframework.util.StreamUtils.copy()
// 像socket中写入返回值，即向浏览器一类请求客户端输出返回值，到此，客户端得到响应
/**
* Copy the contents of the given String to the given output OutputStream.
* Leaves the stream open when done.
* @param in the String to copy from
* @param charset the Charset
* @param out the OutputStream to copy to
* @throws IOException in case of I/O errors
*/
public static void copy(String in, Charset charset, OutputStream out) throws IOException {
Assert.notNull(in, "No input String specified");
Assert.notNull(charset, "No charset specified");
Assert.notNull(out, "No OutputStream specified"); Writer writer = new OutputStreamWriter(out, charset);
writer.write(in);
writer.flush();
}
// return getModelAndView(mavContainer, modelFactory, webRequest);
// RequestMappingHandlerAdapter
// return getModelAndView(mavContainer, modelFactory, webRequest);
// RequestMappingHandlerAdapter
private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,
ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception { // 如果已经处理完成，返回null
modelFactory.updateModel(webRequest, mavContainer);
if (mavContainer.isRequestHandled()) {
return null;
}
// 否则处理 mv
ModelMap model = mavContainer.getModel();
ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());
if (!mavContainer.isViewReference()) {
mav.setView((View) mavContainer.getView());
}
if (model instanceof RedirectAttributes) {
Map<String, ?> flashAttributes = ((RedirectAttributes) model).getFlashAttributes();
HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);
}
return mav;
}
// prepareResponse(response);
// RequestMappingHandlerAdapter
/**
* Prepare the given response according to the settings of this generator.
* Applies the number of cache seconds specified for this generator.
* @param response current HTTP response
* @since 4.2
*/
protected final void prepareResponse(HttpServletResponse response) {
if (this.cacheControl != null) {
applyCacheControl(response, this.cacheControl);
}
else {
applyCacheSeconds(response, this.cacheSeconds);
}
if (servlet3Present && this.varyByRequestHeaders != null) {
for (String value : getVaryRequestHeadersToAdd(response)) {
response.addHeader("Vary", value);
}
}
}
// mappedHandler.applyPostHandle(processedRequest, response, mv);
// org.springframework.web.servlet.HandlerExecutionChain.applyPostHandle(), 调用 interceptor.postHandle()
// org.springframework.web.servlet.HandlerExecutionChain.applyPostHandle(), 调用 interceptor.postHandle()
/**
* Apply postHandle methods of registered interceptors.
*/
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, 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);
}
}
}
// processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
/**
* Handle the result of handler selection and handler invocation, which is
* either a ModelAndView or an Exception to be resolved to a ModelAndView.
*/
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception { boolean errorView = false; // 发生异常，使用 errorView
if (exception != null) {
if (exception instanceof ModelAndViewDefiningException) {
logger.debug("ModelAndViewDefiningException encountered", exception);
mv = ((ModelAndViewDefiningException) exception).getModelAndView();
}
else {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(request, response, handler, exception);
errorView = (mv != null);
}
} // Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
"': assuming HandlerAdapter completed request handling");
}
} if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Concurrent handling started during a forward
return;
} if (mappedHandler != null) {
// 最后再一个触发器钩子，触发 interceptor.afterCompletion()
mappedHandler.triggerAfterCompletion(request, response, null);
}
} /**
* Trigger afterCompletion callbacks on the mapped HandlerInterceptors.
* Will just invoke afterCompletion for all interceptors whose preHandle invocation
* has successfully completed and returned true.
*/
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, 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);
}
}
}
}
// 依次返回 doDispatch()，清理环境
// 返回 FrameworkServlet.doService()
// FrameworkServlet finally中还会触发 requestAttributes.requestCompleted();
// org.springframework.web.context.request.ServletRequestAttributes.requestCompleted()
/**
* Signal that the request has been completed.
* <p>Executes all request destruction callbacks and updates the
* session attributes that have been accessed during request processing.
*/
public void requestCompleted() {
executeRequestDestructionCallbacks();
updateAccessedSessionAttributes();
this.requestActive = false;
} /**
* Execute all callbacks that have been registered for execution
* after request completion.
*/
private void executeRequestDestructionCallbacks() {
synchronized (this.requestDestructionCallbacks) {
for (Runnable runnable : this.requestDestructionCallbacks.values()) {
// 同步调用 DestructionCallbacks.run()
runnable.run();
}
this.requestDestructionCallbacks.clear();
}
} /**
* Update all accessed session attributes through {@code session.setAttribute}
* calls, explicitly indicating to the container that they might have been modified.
*/
@Override
protected void updateAccessedSessionAttributes() {
if (!this.sessionAttributesToUpdate.isEmpty()) {
// Update all affected session attributes.
HttpSession session = getSession(false);
if (session != null) {
try {
for (Map.Entry<String, Object> entry : this.sessionAttributesToUpdate.entrySet()) {
String name = entry.getKey();
Object newValue = entry.getValue();
Object oldValue = session.getAttribute(name);
if (oldValue == newValue && !isImmutableSessionAttribute(name, newValue)) {
session.setAttribute(name, newValue);
}
}
}
catch (IllegalStateException ex) {
// Session invalidated - shouldn't usually happen.
}
}
this.sessionAttributesToUpdate.clear();
}
} // 最后 publishRequestHandledEvent(request, response, startTime, failureCause);
// FrameworkServlet
private void publishRequestHandledEvent(
HttpServletRequest request, HttpServletResponse response, long startTime, Throwable failureCause) { if (this.publishEvents) {
// Whether or not we succeeded, publish an event.
long processingTime = System.currentTimeMillis() - startTime;
int statusCode = (responseGetStatusAvailable ? response.getStatus() : -1);
// 发布 event 到 spring, 使感兴趣的监听者进行相应处理
this.webApplicationContext.publishEvent(
new ServletRequestHandledEvent(this,
request.getRequestURI(), request.getRemoteAddr(),
request.getMethod(), getServletConfig().getServletName(),
WebUtils.getSessionId(request), getUsernameForRequest(request),
processingTime, failureCause, statusCode));
}
}
总结几个技术要点：
1. filterchain 责任链模式的使用；
2. 工厂模式的使用；
3. 拦截器监听；
4. 各功能组件化，职责分明；
5. 模板方法模式使用；
6. mvc；
7. 适配器模式应用；
8. 观察者模式应用；
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