标签：super ons 监听器 cep soft intern 流程图 分享 already
前言SpringMVC是在spring上建立起来的针对web的MVC框架，也是目前非常流行的一款web开发java框架。对于源码的阅读加深对SpringMVC的认识是毋庸置疑的，所以我打算写一篇这样的文章来对SpringMVC做一次深入的学习。
在进入阅读源代码时，我们往往会对一个框架不知从哪里入手。根据SpringMVC请求流程图我们知道这个SpringMVC的核心就是DispatchServlet。所以我们应该从这个类入手。先来看下web.xml文件：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<!--Spring上下文管理配置文件（bean、事务等管理）-->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<!--监听器-->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!--分发器：DispatcherServlet-->
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<!--servlet映射配置-->
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>*.form</url-pattern>
</servlet-mapping>
</web-app>对于web.xml中我们先关注核心：DispatcherServlet。
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package org.springframework.web.servlet;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.i18n.LocaleContext;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.ui.context.ThemeSource;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.async.WebAsyncManager;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.util.NestedServletException;
import org.springframework.web.util.WebUtils;
public class DispatcherServlet extends FrameworkServlet {
public static final String MULTIPART_RESOLVER_BEAN_NAME = "multipartResolver";
public static final String LOCALE_RESOLVER_BEAN_NAME = "localeResolver";
public static final String THEME_RESOLVER_BEAN_NAME = "themeResolver";
public static final String HANDLER_MAPPING_BEAN_NAME = "handlerMapping";
public static final String HANDLER_ADAPTER_BEAN_NAME = "handlerAdapter";
public static final String HANDLER_EXCEPTION_RESOLVER_BEAN_NAME = "handlerExceptionResolver";
public static final String REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME = "viewNameTranslator";
public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver";
public static final String FLASH_MAP_MANAGER_BEAN_NAME = "flashMapManager";
public static final String WEB_APPLICATION_CONTEXT_ATTRIBUTE = DispatcherServlet.class.getName() + ".CONTEXT";
public static final String LOCALE_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".LOCALE_RESOLVER";
public static final String THEME_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_RESOLVER";
public static final String THEME_SOURCE_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_SOURCE";
public static final String INPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".INPUT_FLASH_MAP";
public static final String OUTPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".OUTPUT_FLASH_MAP";
public static final String FLASH_MAP_MANAGER_ATTRIBUTE = DispatcherServlet.class.getName() + ".FLASH_MAP_MANAGER";
public static final String EXCEPTION_ATTRIBUTE = DispatcherServlet.class.getName() + ".EXCEPTION";
public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.servlet.PageNotFound";
private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties";
private static final String DEFAULT_STRATEGIES_PREFIX = "org.springframework.web.servlet";
protected static final Log pageNotFoundLogger = LogFactory.getLog("org.springframework.web.servlet.PageNotFound");
private static final Properties defaultStrategies;
private boolean detectAllHandlerMappings = true;
private boolean detectAllHandlerAdapters = true;
private boolean detectAllHandlerExceptionResolvers = true;
private boolean detectAllViewResolvers = true;
private boolean throwExceptionIfNoHandlerFound = false;
private boolean cleanupAfterInclude = true;
private MultipartResolver multipartResolver;
private LocaleResolver localeResolver;
private ThemeResolver themeResolver;
private List<HandlerMapping> handlerMappings;
private List<HandlerAdapter> handlerAdapters;
private List<HandlerExceptionResolver> handlerExceptionResolvers;
private RequestToViewNameTranslator viewNameTranslator;
private FlashMapManager flashMapManager;
private List<ViewResolver> viewResolvers;
public DispatcherServlet() {
this.setDispatchOptionsRequest(true);
}
public DispatcherServlet(WebApplicationContext webApplicationContext) {
super(webApplicationContext);
this.setDispatchOptionsRequest(true);
}
public void setDetectAllHandlerMappings(boolean detectAllHandlerMappings) {
this.detectAllHandlerMappings = detectAllHandlerMappings;
}
public void setDetectAllHandlerAdapters(boolean detectAllHandlerAdapters) {
this.detectAllHandlerAdapters = detectAllHandlerAdapters;
}
public void setDetectAllHandlerExceptionResolvers(boolean detectAllHandlerExceptionResolvers) {
this.detectAllHandlerExceptionResolvers = detectAllHandlerExceptionResolvers;
}
public void setDetectAllViewResolvers(boolean detectAllViewResolvers) {
this.detectAllViewResolvers = detectAllViewResolvers;
}
public void setThrowExceptionIfNoHandlerFound(boolean throwExceptionIfNoHandlerFound) {
this.throwExceptionIfNoHandlerFound = throwExceptionIfNoHandlerFound;
}
public void setCleanupAfterInclude(boolean cleanupAfterInclude) {
this.cleanupAfterInclude = cleanupAfterInclude;
}
protected void onRefresh(ApplicationContext context) {
this.initStrategies(context);
}
protected void initStrategies(ApplicationContext context) {
this.initMultipartResolver(context);
this.initLocaleResolver(context);
this.initThemeResolver(context);
this.initHandlerMappings(context);
this.initHandlerAdapters(context);
this.initHandlerExceptionResolvers(context);
this.initRequestToViewNameTranslator(context);
this.initViewResolvers(context);
this.initFlashMapManager(context);
}
private void initMultipartResolver(ApplicationContext context) {
try {
this.multipartResolver = (MultipartResolver)context.getBean("multipartResolver", MultipartResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using MultipartResolver [" + this.multipartResolver + "]");
}
} catch (NoSuchBeanDefinitionException var3) {
this.multipartResolver = null;
if (this.logger.isDebugEnabled()) {
this.logger.debug("Unable to locate MultipartResolver with name ‘multipartResolver‘: no multipart request handling provided");
}
}
}
private void initLocaleResolver(ApplicationContext context) {
try {
this.localeResolver = (LocaleResolver)context.getBean("localeResolver", LocaleResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using LocaleResolver [" + this.localeResolver + "]");
}
} catch (NoSuchBeanDefinitionException var3) {
this.localeResolver = (LocaleResolver)this.getDefaultStrategy(context, LocaleResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Unable to locate LocaleResolver with name ‘localeResolver‘: using default [" + this.localeResolver + "]");
}
}
}
private void initThemeResolver(ApplicationContext context) {
try {
this.themeResolver = (ThemeResolver)context.getBean("themeResolver", ThemeResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using ThemeResolver [" + this.themeResolver + "]");
}
} catch (NoSuchBeanDefinitionException var3) {
this.themeResolver = (ThemeResolver)this.getDefaultStrategy(context, ThemeResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Unable to locate ThemeResolver with name ‘themeResolver‘: using default [" + this.themeResolver + "]");
}
}
}
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
Map<String, HandlerMapping> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList(matchingBeans.values());
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
} else {
try {
HandlerMapping hm = (HandlerMapping)context.getBean("handlerMapping", HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
} catch (NoSuchBeanDefinitionException var3) {
;
}
}
if (this.handlerMappings == null) {
this.handlerMappings = this.getDefaultStrategies(context, HandlerMapping.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("No HandlerMappings found in servlet ‘" + this.getServletName() + "‘: using default");
}
}
}
private void initHandlerAdapters(ApplicationContext context) {
this.handlerAdapters = null;
if (this.detectAllHandlerAdapters) {
Map<String, HandlerAdapter> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerAdapters = new ArrayList(matchingBeans.values());
AnnotationAwareOrderComparator.sort(this.handlerAdapters);
}
} else {
try {
HandlerAdapter ha = (HandlerAdapter)context.getBean("handlerAdapter", HandlerAdapter.class);
this.handlerAdapters = Collections.singletonList(ha);
} catch (NoSuchBeanDefinitionException var3) {
;
}
}
if (this.handlerAdapters == null) {
this.handlerAdapters = this.getDefaultStrategies(context, HandlerAdapter.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("No HandlerAdapters found in servlet ‘" + this.getServletName() + "‘: using default");
}
}
}
private void initHandlerExceptionResolvers(ApplicationContext context) {
this.handlerExceptionResolvers = null;
if (this.detectAllHandlerExceptionResolvers) {
Map<String, HandlerExceptionResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerExceptionResolvers = new ArrayList(matchingBeans.values());
AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers);
}
} else {
try {
HandlerExceptionResolver her = (HandlerExceptionResolver)context.getBean("handlerExceptionResolver", HandlerExceptionResolver.class);
this.handlerExceptionResolvers = Collections.singletonList(her);
} catch (NoSuchBeanDefinitionException var3) {
;
}
}
if (this.handlerExceptionResolvers == null) {
this.handlerExceptionResolvers = this.getDefaultStrategies(context, HandlerExceptionResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("No HandlerExceptionResolvers found in servlet ‘" + this.getServletName() + "‘: using default");
}
}
}
private void initRequestToViewNameTranslator(ApplicationContext context) {
try {
this.viewNameTranslator = (RequestToViewNameTranslator)context.getBean("viewNameTranslator", RequestToViewNameTranslator.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using RequestToViewNameTranslator [" + this.viewNameTranslator + "]");
}
} catch (NoSuchBeanDefinitionException var3) {
this.viewNameTranslator = (RequestToViewNameTranslator)this.getDefaultStrategy(context, RequestToViewNameTranslator.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Unable to locate RequestToViewNameTranslator with name ‘viewNameTranslator‘: using default [" + this.viewNameTranslator + "]");
}
}
}
private void initViewResolvers(ApplicationContext context) {
this.viewResolvers = null;
if (this.detectAllViewResolvers) {
Map<String, ViewResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, ViewResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.viewResolvers = new ArrayList(matchingBeans.values());
AnnotationAwareOrderComparator.sort(this.viewResolvers);
}
} else {
try {
ViewResolver vr = (ViewResolver)context.getBean("viewResolver", ViewResolver.class);
this.viewResolvers = Collections.singletonList(vr);
} catch (NoSuchBeanDefinitionException var3) {
;
}
}
if (this.viewResolvers == null) {
this.viewResolvers = this.getDefaultStrategies(context, ViewResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("No ViewResolvers found in servlet ‘" + this.getServletName() + "‘: using default");
}
}
}
private void initFlashMapManager(ApplicationContext context) {
try {
this.flashMapManager = (FlashMapManager)context.getBean("flashMapManager", FlashMapManager.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using FlashMapManager [" + this.flashMapManager + "]");
}
} catch (NoSuchBeanDefinitionException var3) {
this.flashMapManager = (FlashMapManager)this.getDefaultStrategy(context, FlashMapManager.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Unable to locate FlashMapManager with name ‘flashMapManager‘: using default [" + this.flashMapManager + "]");
}
}
}
public final ThemeSource getThemeSource() {
return this.getWebApplicationContext() instanceof ThemeSource ? (ThemeSource)this.getWebApplicationContext() : null;
}
public final MultipartResolver getMultipartResolver() {
return this.multipartResolver;
}
protected <T> T getDefaultStrategy(ApplicationContext context, Class<T> strategyInterface) {
List<T> strategies = this.getDefaultStrategies(context, strategyInterface);
if (strategies.size() != 1) {
throw new BeanInitializationException("DispatcherServlet needs exactly 1 strategy for interface [" + strategyInterface.getName() + "]");
} else {
return strategies.get(0);
}
}
protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
String key = strategyInterface.getName();
String value = defaultStrategies.getProperty(key);
if (value == null) {
return new LinkedList();
} else {
String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
List<T> strategies = new ArrayList(classNames.length);
String[] var7 = classNames;
int var8 = classNames.length;
for(int var9 = 0; var9 < var8; ++var9) {
String className = var7[var9];
try {
Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
Object strategy = this.createDefaultStrategy(context, clazz);
strategies.add(strategy);
} catch (ClassNotFoundException var13) {
throw new BeanInitializationException("Could not find DispatcherServlet‘s default strategy class [" + className + "] for interface [" + key + "]", var13);
} catch (LinkageError var14) {
throw new BeanInitializationException("Error loading DispatcherServlet‘s default strategy class [" + className + "] for interface [" + key + "]: problem with class file or dependent class", var14);
}
}
return strategies;
}
}
protected Object createDefaultStrategy(ApplicationContext context, Class<?> clazz) {
return context.getAutowireCapableBeanFactory().createBean(clazz);
}
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
if (this.logger.isDebugEnabled()) {
String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : "";
this.logger.debug("DispatcherServlet with name ‘" + this.getServletName() + "‘" + resumed + " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]");
}
Map<String, Object> attributesSnapshot = null;
if (WebUtils.isIncludeRequest(request)) {
attributesSnapshot = new HashMap();
Enumeration attrNames = request.getAttributeNames();
label108:
while(true) {
String attrName;
do {
if (!attrNames.hasMoreElements()) {
break label108;
}
attrName = (String)attrNames.nextElement();
} while(!this.cleanupAfterInclude && !attrName.startsWith("org.springframework.web.servlet"));
attributesSnapshot.put(attrName, request.getAttribute(attrName));
}
}
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.getWebApplicationContext());
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
request.setAttribute(THEME_SOURCE_ATTRIBUTE, this.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 {
this.doDispatch(request, response);
} finally {
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted() && attributesSnapshot != null) {
this.restoreAttributesAfterInclude(request, attributesSnapshot);
}
}
}
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
try {
ModelAndView mv = null;
Object dispatchException = null;
try {
processedRequest = this.checkMultipart(request);
multipartRequestParsed = processedRequest != request;
mappedHandler = this.getHandler(processedRequest);
if (mappedHandler == null || mappedHandler.getHandler() == null) {
this.noHandlerFound(processedRequest, response);
return;
}
HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (this.logger.isDebugEnabled()) {
this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
this.applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv);
} catch (Exception var20) {
dispatchException = var20;
} catch (Throwable var21) {
dispatchException = new NestedServletException("Handler dispatch failed", var21);
}
this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException);
} catch (Exception var22) {
this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22);
} catch (Throwable var23) {
this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", var23));
}
} finally {
if (asyncManager.isConcurrentHandlingStarted()) {
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
} else if (multipartRequestParsed) {
this.cleanupMultipart(processedRequest);
}
}
}
private void applyDefaultViewName(HttpServletRequest request, ModelAndView mv) throws Exception {
if (mv != null && !mv.hasView()) {
mv.setViewName(this.getDefaultViewName(request));
}
}
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception {
boolean errorView = false;
if (exception != null) {
if (exception instanceof ModelAndViewDefiningException) {
this.logger.debug("ModelAndViewDefiningException encountered", exception);
mv = ((ModelAndViewDefiningException)exception).getModelAndView();
} else {
Object handler = mappedHandler != null ? mappedHandler.getHandler() : null;
mv = this.processHandlerException(request, response, handler, exception);
errorView = mv != null;
}
}
if (mv != null && !mv.wasCleared()) {
this.render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
} else if (this.logger.isDebugEnabled()) {
this.logger.debug("Null ModelAndView returned to DispatcherServlet with name ‘" + this.getServletName() + "‘: assuming HandlerAdapter completed request handling");
}
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, (Exception)null);
}
}
}
protected LocaleContext buildLocaleContext(final HttpServletRequest request) {
return this.localeResolver instanceof LocaleContextResolver ? ((LocaleContextResolver)this.localeResolver).resolveLocaleContext(request) : new LocaleContext() {
public Locale getLocale() {
return DispatcherServlet.this.localeResolver.resolveLocale(request);
}
};
}
protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException {
if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) {
if (WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class) != null) {
this.logger.debug("Request is already a MultipartHttpServletRequest - if not in a forward, this typically results from an additional MultipartFilter in web.xml");
} else if (this.hasMultipartException(request)) {
this.logger.debug("Multipart resolution failed for current request before - skipping re-resolution for undisturbed error rendering");
} else {
try {
return this.multipartResolver.resolveMultipart(request);
} catch (MultipartException var3) {
if (request.getAttribute("javax.servlet.error.exception") == null) {
throw var3;
}
}
this.logger.debug("Multipart resolution failed for error dispatch", var3);
}
}
return request;
}
private boolean hasMultipartException(HttpServletRequest request) {
for(Throwable error = (Throwable)request.getAttribute("javax.servlet.error.exception"); error != null; error = error.getCause()) {
if (error instanceof MultipartException) {
return true;
}
}
return false;
}
protected void cleanupMultipart(HttpServletRequest request) {
MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest)WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class);
if (multipartRequest != null) {
this.multipartResolver.cleanupMultipart(multipartRequest);
}
}
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Iterator var2 = this.handlerMappings.iterator();
HandlerExecutionChain handler;
do {
if (!var2.hasNext()) {
return null;
}
HandlerMapping hm = (HandlerMapping)var2.next();
if (this.logger.isTraceEnabled()) {
this.logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name ‘" + this.getServletName() + "‘");
}
handler = hm.getHandler(request);
} while(handler == null);
return handler;
}
protected void noHandlerFound(HttpServletRequest request, HttpServletResponse response) throws Exception {
if (pageNotFoundLogger.isWarnEnabled()) {
pageNotFoundLogger.warn("No mapping found for HTTP request with URI [" + getRequestUri(request) + "] in DispatcherServlet with name ‘" + this.getServletName() + "‘");
}
if (this.throwExceptionIfNoHandlerFound) {
throw new NoHandlerFoundException(request.getMethod(), getRequestUri(request), (new ServletServerHttpRequest(request)).getHeaders());
} else {
response.sendError(404);
}
}
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
Iterator var2 = this.handlerAdapters.iterator();
HandlerAdapter ha;
do {
if (!var2.hasNext()) {
throw new ServletException("No adapter for handler [" + handler + "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
}
ha = (HandlerAdapter)var2.next();
if (this.logger.isTraceEnabled()) {
this.logger.trace("Testing handler adapter [" + ha + "]");
}
} while(!ha.supports(handler));
return ha;
}
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
ModelAndView exMv = null;
Iterator var6 = this.handlerExceptionResolvers.iterator();
while(var6.hasNext()) {
HandlerExceptionResolver handlerExceptionResolver = (HandlerExceptionResolver)var6.next();
exMv = handlerExceptionResolver.resolveException(request, response, handler, ex);
if (exMv != null) {
break;
}
}
if (exMv != null) {
if (exMv.isEmpty()) {
request.setAttribute(EXCEPTION_ATTRIBUTE, ex);
return null;
} else {
if (!exMv.hasView()) {
exMv.setViewName(this.getDefaultViewName(request));
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Handler execution resulted in exception - forwarding to resolved error view: " + exMv, ex);
}
WebUtils.exposeErrorRequestAttributes(request, ex, this.getServletName());
return exMv;
}
} else {
throw ex;
}
}
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
Locale locale = this.localeResolver.resolveLocale(request);
response.setLocale(locale);
View view;
if (mv.isReference()) {
view = this.resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);
if (view == null) {
throw new ServletException("Could not resolve view with name ‘" + mv.getViewName() + "‘ in servlet with name ‘" + this.getServletName() + "‘");
}
} else {
view = mv.getView();
if (view == null) {
throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a View object in servlet with name ‘" + this.getServletName() + "‘");
}
}
if (this.logger.isDebugEnabled()) {
this.logger.debug("Rendering view [" + view + "] in DispatcherServlet with name ‘" + this.getServletName() + "‘");
}
try {
if (mv.getStatus() != null) {
response.setStatus(mv.getStatus().value());
}
view.render(mv.getModelInternal(), request, response);
} catch (Exception var7) {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name ‘" + this.getServletName() + "‘", var7);
}
throw var7;
}
}
protected String getDefaultViewName(HttpServletRequest request) throws Exception {
return this.viewNameTranslator.getViewName(request);
}
protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception {
Iterator var5 = this.viewResolvers.iterator();
View view;
do {
if (!var5.hasNext()) {
return null;
}
ViewResolver viewResolver = (ViewResolver)var5.next();
view = viewResolver.resolveViewName(viewName, locale);
} while(view == null);
return view;
}
private void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, Exception ex) throws Exception {
if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, ex);
}
throw ex;
}
private void restoreAttributesAfterInclude(HttpServletRequest request, Map<?, ?> attributesSnapshot) {
Set<String> attrsToCheck = new HashSet();
Enumeration attrNames = request.getAttributeNames();
while(true) {
String attrName;
do {
if (!attrNames.hasMoreElements()) {
attrsToCheck.addAll(attributesSnapshot.keySet());
Iterator var8 = attrsToCheck.iterator();
while(var8.hasNext()) {
String attrName = (String)var8.next();
Object attrValue = attributesSnapshot.get(attrName);
if (attrValue == null) {
request.removeAttribute(attrName);
} else if (attrValue != request.getAttribute(attrName)) {
request.setAttribute(attrName, attrValue);
}
}
return;
}
attrName = (String)attrNames.nextElement();
} while(!this.cleanupAfterInclude && !attrName.startsWith("org.springframework.web.servlet"));
attrsToCheck.add(attrName);
}
}
private static String getRequestUri(HttpServletRequest request) {
String uri = (String)request.getAttribute("javax.servlet.include.request_uri");
if (uri == null) {
uri = request.getRequestURI();
}
return uri;
}
static {
try {
ClassPathResource resource = new ClassPathResource("DispatcherServlet.properties", DispatcherServlet.class);
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
} catch (IOException var1) {
throw new IllegalStateException("Could not load ‘DispatcherServlet.properties‘: " + var1.getMessage());
}
}
}
其实它就是一个Servlet的子类，继承了FrameworkServlet类，除去那些属性的setter方法之外我们可以关注两个点：构造函数和initStrategies方法。
private MultipartResolver multipartResolver;
private LocaleResolver localeResolver;
private ThemeResolver themeResolver;
// HandlerMapping干啥的？
private List<HandlerMapping> handlerMappings;
// HandlerAdapter干哈的？
private List<HandlerAdapter> handlerAdapters;
private List<HandlerExceptionResolver> handlerExceptionResolvers;
private RequestToViewNameTranslator viewNameTranslator;
private FlashMapManager flashMapManager;
// ViewResolver干哈的？
private List<ViewResolver> viewResolvers;
// 通过webApplicationContext构造函数
public DispatcherServlet(WebApplicationContext webApplicationContext) {
// 这里需要查看FrameworkServlet构造函数
super(webApplicationContext);
this.setDispatchOptionsRequest(true);
}
// FrameworkServlet构造函数
public FrameworkServlet(WebApplicationContext webApplicationContext) {
this.contextClass = DEFAULT_CONTEXT_CLASS;
this.contextInitializers = new ArrayList();
this.publishContext = true;
this.publishEvents = true;
this.threadContextInheritable = false;
this.dispatchOptionsRequest = false;
this.dispatchTraceRequest = false;
this.webApplicationContextInjected = false;
this.refreshEventReceived = false;
this.webApplicationContext = webApplicationContext;
}
// 从ApplicationContext初始化成员变量，装载
protected void initStrategies(ApplicationContext context) {
this.initMultipartResolver(context);
this.initLocaleResolver(context);
this.initThemeResolver(context);
this.initHandlerMappings(context);
this.initHandlerAdapters(context);
this.initHandlerExceptionResolvers(context);
this.initRequestToViewNameTranslator(context);
this.initViewResolvers(context);
this.initFlashMapManager(context);
}
// 其中一个初始化方法，通过BeanFactory获取bean
private void initMultipartResolver(ApplicationContext context) {
try {
this.multipartResolver = (MultipartResolver)context.getBean("multipartResolver", MultipartResolver.class);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Using MultipartResolver [" + this.multipartResolver + "]");
}
} catch (NoSuchBeanDefinitionException var3) {
this.multipartResolver = null;
if (this.logger.isDebugEnabled()) {
this.logger.debug("Unable to locate MultipartResolver with name ‘multipartResolver‘: no multipart request handling provided");
}
}
}通过上面的代码我们知道，项目入口在web.xml中，SpringMVC的bean是由Springcontext容器管理，在DispatchServlet中通过BeanFactory去装载bean，也就是初始化HandlerMapping、HandlerAdapter、ViewResolver、MultipartResolver、ThemeResolver、FlashMapManager等成员变量。
那么这些成员变量都是用来干什么的呢？我们接下来一步一步的看各个变量的源码。
package org.springframework.web.multipart;
import javax.servlet.http.HttpServletRequest;
public interface MultipartResolver {
boolean isMultipart(HttpServletRequest var1);
MultipartHttpServletRequest resolveMultipart(HttpServletRequest var1) throws MultipartException;
void cleanupMultipart(MultipartHttpServletRequest var1);
}
这其实就是一个HttpServlet文件上传接口。实现这些接口的类：CommonsMultipartResolver，StandardServletMultipartResolver
package org.springframework.web.multipart.support;
import java.util.Iterator;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.Part;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
public class StandardServletMultipartResolver implements MultipartResolver {
private boolean resolveLazily = false;
public StandardServletMultipartResolver() {
}
public void setResolveLazily(boolean resolveLazily) {
this.resolveLazily = resolveLazily;
}
public boolean isMultipart(HttpServletRequest request) {
if (!"post".equalsIgnoreCase(request.getMethod())) {
return false;
} else {
String contentType = request.getContentType();
return StringUtils.startsWithIgnoreCase(contentType, "multipart/");
}
}
public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException {
return new StandardMultipartHttpServletRequest(request, this.resolveLazily);
}
public void cleanupMultipart(MultipartHttpServletRequest request) {
if (!(request instanceof AbstractMultipartHttpServletRequest) || ((AbstractMultipartHttpServletRequest)request).isResolved()) {
try {
Iterator var2 = request.getParts().iterator();
while(var2.hasNext()) {
Part part = (Part)var2.next();
if (request.getFile(part.getName()) != null) {
part.delete();
}
}
} catch (Throwable var4) {
LogFactory.getLog(this.getClass()).warn("Failed to perform cleanup of multipart items", var4);
}
}
}
}
package org.springframework.web.multipart.commons;
import java.util.List;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileUpload;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.springframework.util.Assert;
import org.springframework.web.context.ServletContextAware;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.multipart.commons.CommonsFileUploadSupport.MultipartParsingResult;
import org.springframework.web.multipart.support.AbstractMultipartHttpServletRequest;
import org.springframework.web.multipart.support.DefaultMultipartHttpServletRequest;
import org.springframework.web.util.WebUtils;
public class CommonsMultipartResolver extends CommonsFileUploadSupport implements MultipartResolver, ServletContextAware {
private boolean resolveLazily;
public CommonsMultipartResolver() {
this.resolveLazily = false;
}
public CommonsMultipartResolver(ServletContext servletContext) {
this();
this.setServletContext(servletContext);
}
public void setResolveLazily(boolean resolveLazily) {
this.resolveLazily = resolveLazily;
}
protected FileUpload newFileUpload(FileItemFactory fileItemFactory) {
return new ServletFileUpload(fileItemFactory);
}
public void setServletContext(ServletContext servletContext) {
if (!this.isUploadTempDirSpecified()) {
this.getFileItemFactory().setRepository(WebUtils.getTempDir(servletContext));
}
}
public boolean isMultipart(HttpServletRequest request) {
return request != null && ServletFileUpload.isMultipartContent(request);
}
public MultipartHttpServletRequest resolveMultipart(final HttpServletRequest request) throws MultipartException {
Assert.notNull(request, "Request must not be null");
if (this.resolveLazily) {
return new DefaultMultipartHttpServletRequest(request) {
protected void initializeMultipart() {
MultipartParsingResult parsingResult = CommonsMultipartResolver.this.parseRequest(request);
this.setMultipartFiles(parsingResult.getMultipartFiles());
this.setMultipartParameters(parsingResult.getMultipartParameters());
this.setMultipartParameterContentTypes(parsingResult.getMultipartParameterContentTypes());
}
};
} else {
MultipartParsingResult parsingResult = this.parseRequest(request);
return new DefaultMultipartHttpServletRequest(request, parsingResult.getMultipartFiles(), parsingResult.getMultipartParameters(), parsingResult.getMultipartParameterContentTypes());
}
}
protected MultipartParsingResult parseRequest(HttpServletRequest request) throws MultipartException {
String encoding = this.determineEncoding(request);
FileUpload fileUpload = this.prepareFileUpload(encoding);
try {
List<FileItem> fileItems = ((ServletFileUpload)fileUpload).parseRequest(request);
return this.parseFileItems(fileItems, encoding);
} catch (SizeLimitExceededException var5) {
throw new MaxUploadSizeExceededException(fileUpload.getSizeMax(), var5);
} catch (FileSizeLimitExceededException var6) {
throw new MaxUploadSizeExceededException(fileUpload.getFileSizeMax(), var6);
} catch (FileUploadException var7) {
throw new MultipartException("Failed to parse multipart servlet request", var7);
}
}
protected String determineEncoding(HttpServletRequest request) {
String encoding = request.getCharacterEncoding();
if (encoding == null) {
encoding = this.getDefaultEncoding();
}
return encoding;
}
public void cleanupMultipart(MultipartHttpServletRequest request) {
if (!(request instanceof AbstractMultipartHttpServletRequest) || ((AbstractMultipartHttpServletRequest)request).isResolved()) {
try {
this.cleanupFileItems(request.getMultiFileMap());
} catch (Throwable var3) {
this.logger.warn("Failed to perform multipart cleanup for servlet request", var3);
}
}
}
}通常这个的配置我们也会在Spring-conext中配置管理。
package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
public interface HandlerMapping {
String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping";
String BEST_MATCHING_PATTERN_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingPattern";
String INTROSPECT_TYPE_LEVEL_MAPPING = HandlerMapping.class.getName() + ".introspectTypeLevelMapping";
String URI_TEMPLATE_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".uriTemplateVariables";
String MATRIX_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".matrixVariables";
String PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE = HandlerMapping.class.getName() + ".producibleMediaTypes";
HandlerExecutionChain getHandler(HttpServletRequest var1) throws Exception;
}这个handlerMapping：根据【请求】找到【处理器Handler】，但并不是简单的返回处理器，而是将处理器和拦截器封装，形成一个处理器执行链(HandlerExecuteChain)。
package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public interface HandlerAdapter {
boolean supports(Object var1);
ModelAndView handle(HttpServletRequest var1, HttpServletResponse var2, Object var3) throws Exception;
long getLastModified(HttpServletRequest var1, Object var2);
}通过HandlerMapping获取了执行链，那么这里就需要将执行链交给HandlerAdapter适配对应的handler处理，这个handler可以简单理解为就是controller中的某个映射方法。处理完后返回ModelAndView。
package org.springframework.web.servlet;
import java.util.Locale;
public interface ViewResolver {
View resolveViewName(String var1, Locale var2) throws Exception;
}
// DispatchServlet中方法
protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception {
Iterator var5 = this.viewResolvers.iterator();
View view;
do {
if (!var5.hasNext()) {
return null;
}
ViewResolver viewResolver = (ViewResolver)var5.next();
view = viewResolver.resolveViewName(viewName, locale);
} while(view == null);
return view;
}
处理完后的ModelAndView交到DispatchServlet后需要交给ViewResolver进行解析成View，在View中模板数据装配完成后交回给DispatchServlet，然后响应给客户端。
备注：做好结合打断点的方式追踪这个请求过程，对于理解这个流程是非常有作用的，特别是初学者。这里很多细节没有披露出来，如果有些地方有问题，你可以留意告诉我，我会第一时间改正，以防误导读者。谢谢。
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原文地址：http://blog.51cto.com/4837471/2330956
