SpringMVC源码-DispatcherServlet初始化
web容器启动后会实例化Servlet，会执行Servlet的init方法且只会执行一次。后续调用doService处理客户请求。
DispatcherServlet的构造方法
public DispatcherServlet() {
super();
setDispatchOptionsRequest(true);
}
调用了父类的构造方法，设置dispatchOptionsRequest属性为true。
HttpServletBean.init()
public final void init() throws ServletException {
// Set bean properties from init parameters.
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
if (!pvs.isEmpty()) {
try {
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
initBeanWrapper(bw);
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
if (logger.isErrorEnabled()) {
logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
}
throw ex;
}
}
// Let subclasses do whatever initialization they like.
initServletBean();
}
1、ServletConfigPropertyValues从ServletConfig获取属性值并添加到ServletConfigPropertyValues对象中，同时检查必须的属性值
2、若从第一步获取的属性值PropertyValues非空，调用PropertyAccessorFactory.forBeanPropertyAccess将DispatcherServlet封装成BeanWrapper，BeanWrapper注册Resource自定义属性编辑器ResourceEditor，调用initBeanWrapper初始化BeanWrapper，将从第一步获取的属性值PropertyValues设置到BeanWrapper
3、initServletBean
ServletConfigPropertyValues
public ServletConfigPropertyValues(ServletConfig config, Set<String> requiredProperties)
throws ServletException {
Set<String> missingProps = (!CollectionUtils.isEmpty(requiredProperties) ?
new HashSet<>(requiredProperties) : null);
Enumeration<String> paramNames = config.getInitParameterNames();
while (paramNames.hasMoreElements()) {
String property = paramNames.nextElement();
Object value = config.getInitParameter(property);
addPropertyValue(new PropertyValue(property, value));
if (missingProps != null) {
missingProps.remove(property);
}
}
// Fail if we are still missing properties.
if (!CollectionUtils.isEmpty(missingProps)) {
throw new ServletException(
"Initialization from ServletConfig for servlet '" + config.getServletName() +
"' failed; the following required properties were missing: " +
StringUtils.collectionToDelimitedString(missingProps, ", "));
}
}
1、由requiredProperties属性List构造出missingProps集合
2、从ServletConfig获取初始参数名列表
3、遍历第二步的集合，从ServletConfig获取属性值并添加到PropertyValue，同时将该属性从missingProps中移除
4.若missingProps不为空，即ServletConfig缺失必须的属性值则抛出异常
FrameworkServlet.initServletBean()
protected final void initServletBean() throws ServletException {
getServletContext().log("Initializing Spring " + getClass().getSimpleName() + " '" + getServletName() + "'");
if (logger.isInfoEnabled()) {
logger.info("Initializing Servlet '" + getServletName() + "'");
}
long startTime = System.currentTimeMillis();
try {
this.webApplicationContext = initWebApplicationContext();
initFrameworkServlet();
}
catch (ServletException | RuntimeException ex) {
logger.error("Context initialization failed", ex);
throw ex;
}
if (logger.isDebugEnabled()) {
String value = this.enableLoggingRequestDetails ?
"shown which may lead to unsafe logging of potentially sensitive data" :
"masked to prevent unsafe logging of potentially sensitive data";
logger.debug("enableLoggingRequestDetails='" + this.enableLoggingRequestDetails +
"': request parameters and headers will be " + value);
}
if (logger.isInfoEnabled()) {
logger.info("Completed initialization in " + (System.currentTimeMillis() - startTime) + " ms");
}
}
1、initWebApplicationContext初始化WebApplicationContext
2、initFrameworkServlet（空方法）
FrameworkServlet.initWebApplicationContext()
protected WebApplicationContext initWebApplicationContext() {
WebApplicationContext rootContext =
WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = null;
if (this.webApplicationContext != null) {
// A context instance was injected at construction time -> use it
wac = this.webApplicationContext;
if (wac instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent -> set
// the root application context (if any; may be null) as the parent
cwac.setParent(rootContext);
}
configureAndRefreshWebApplicationContext(cwac);
}
}
}
if (wac == null) {
// No context instance was injected at construction time -> see if one
// has been registered in the servlet context. If one exists, it is assumed
// that the parent context (if any) has already been set and that the
// user has performed any initialization such as setting the context id
wac = findWebApplicationContext();
}
if (wac == null) {
// No context instance is defined for this servlet -> create a local one
wac = createWebApplicationContext(rootContext);
}
if (!this.refreshEventReceived) {
// Either the context is not a ConfigurableApplicationContext with refresh
// support or the context injected at construction time had already been
// refreshed -> trigger initial onRefresh manually here.
synchronized (this.onRefreshMonitor) {
onRefresh(wac);
}
}
if (this.publishContext) {
// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
}
return wac;
}
1、WebApplicationContextUtils.getWebApplicationContext通过WebApplicationContext.class.getName() + ".ROOT"名从ServletContext中获取属性值，即ContextLoaderListener在初始化上下文时创建的Spring WebApplicationContext上下文对象
2、判断当前上下文webApplicationContext是否非空，且是ConfigurableWebApplicationContext类型，且未活动则设置父上下文为从第一部获取的WebApplicationContext，调用configureAndRefreshWebApplicationContext配置和刷新上下文
3、如果当前上下文为空findWebApplicationContext获取当前上下文
4、如果当前上下文为空createWebApplicationContext创建当前上下文
5、refreshEventReceived为false，调用onRefresh
6、publishContext为true，FrameworkServlet.class.getName() + ".CONTEXT."+getServletName()为key，当前上下文为value设置到ServletContext
FrameworkServlet.findWebApplicationContext()
protected WebApplicationContext findWebApplicationContext() {
String attrName = getContextAttribute();
if (attrName == null) {
return null;
}
WebApplicationContext wac =
WebApplicationContextUtils.getWebApplicationContext(getServletContext(), attrName);
if (wac == null) {
throw new IllegalStateException("No WebApplicationContext found: initializer not registered?");
}
return wac;
}
1、getContextAttribute获取属性值，默认为null
2、若第一步的属性值为null，直接返回null
3、否则WebApplicationContextUtils.getWebApplicationContext从ServletContext获取上下文，若获取不到抛出异常，获取到了返回
FrameworkServlet.createWebApplicationContext(@Nullable WebApplicationContext parent)
protected WebApplicationContext createWebApplicationContext(@Nullable WebApplicationContext parent) {
return createWebApplicationContext((ApplicationContext) parent);
}
FrameworkServlet.createWebApplicationContext(@Nullable ApplicationContext parent)
protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
Class<?> contextClass = getContextClass();
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException(
"Fatal initialization error in servlet with name '" + getServletName() +
"': custom WebApplicationContext class [" + contextClass.getName() +
"] is not of type ConfigurableWebApplicationContext");
}
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
wac.setEnvironment(getEnvironment());
wac.setParent(parent);
String configLocation = getContextConfigLocation();
if (configLocation != null) {
wac.setConfigLocation(configLocation);
}
configureAndRefreshWebApplicationContext(wac);
return wac;
}
1、getContextClass获取contextClass，是XmlWebApplicationContext类型
private Class<?> contextClass = DEFAULT_CONTEXT_CLASS;
public static final Class<?> DEFAULT_CONTEXT_CLASS = XmlWebApplicationContext.class;
2、BeanUtils.instantiateClass实例化contextClass为ConfigurableWebApplicationContext
3、ConfigurableWebApplicationContext设置Environment和父上下文parent
4、getContextConfigLocation获取contextConfigLocation，即web.xml中servlet下配置init-param参数：
<servlet>
<servlet-name>dispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
<async-supported>true</async-supported>
</servlet>
5、configureAndRefreshWebApplicationContext配置和刷新ConfigurableWebApplicationContext
6、返回
FrameworkServlet.configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac)
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
if (this.contextId != null) {
wac.setId(this.contextId);
}
else {
// Generate default id...
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
}
}
wac.setServletContext(getServletContext());
wac.setServletConfig(getServletConfig());
wac.setNamespace(getNamespace());
wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));
// The wac environment's #initPropertySources will be called in any case when the context
// is refreshed; do it eagerly here to ensure servlet property sources are in place for
// use in any post-processing or initialization that occurs below prior to #refresh
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
}
postProcessWebApplicationContext(wac);
applyInitializers(wac);
wac.refresh();
}
1、ConfigurableWebApplicationContext设置id
2、ConfigurableWebApplicationContext设置ServletContext和ServletConfig,设置Namespace
3、添加ApplicationListener监听器ContextRefreshListener
4、获取Environment并调用initPropertySources替换servletContextInitParams和servletConfigInitParams参数
5、postProcessWebApplicationContext
6、applyInitializers在ConfigurableWebApplicationContext刷新之前将globalInitializerClasses参数解析成ApplicationContextInitializer并调用ApplicationContextInitializer.initialize
7、刷新容器，对mvc.xml文件解析成BeanDifinition，创建bean，在下篇文章进行。
ContextRefreshListener
private class ContextRefreshListener implements ApplicationListener<ContextRefreshedEvent> {
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
FrameworkServlet.this.onApplicationEvent(event);
}
}
ContextRefreshListener监听ContextRefreshedEvent事件，当ContextRefreshedEvent事件发生时，执行onApplicationEvent。上面调用refresh()方法时，会发布ContextRefreshedEvent事件。
FrameworkServlet.onApplicationEvent(ContextRefreshedEvent event)
public void onApplicationEvent(ContextRefreshedEvent event) {
this.refreshEventReceived = true;
synchronized (this.onRefreshMonitor) {
onRefresh(event.getApplicationContext());
}
}
1、设置refreshEventReceived为true
private volatile boolean refreshEventReceived;
2、执行onRefresh
onRefresh(ApplicationContext context)
protected void onRefresh(ApplicationContext context) {
initStrategies(context);
}
initStrategies(ApplicationContext context)
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
initStrategies初始化SpringMVC处理请求所需的组件。这些组件的创建和解析是通过mvc.xml文件配置实现的，主要是mvc:annotation-driven/。
DispatcherServlet.initMultipartResolver(ApplicationContext context)
private void initMultipartResolver(ApplicationContext context) {
try {
this.multipartResolver = context.getBean(MULTIPART_RESOLVER_BEAN_NAME, MultipartResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.multipartResolver);
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.multipartResolver.getClass().getSimpleName());
}
}
catch (NoSuchBeanDefinitionException ex) {
// Default is no multipart resolver.
this.multipartResolver = null;
if (logger.isTraceEnabled()) {
logger.trace("No MultipartResolver '" + MULTIPART_RESOLVER_BEAN_NAME + "' declared");
}
}
}
从ApplicationContext中获取所有类型为MultipartResolver的bean并且设置到multipartResolver。出现异常调用getDefaultStrategies获取MultipartResolver。MultipartResolver用于上传文件处理。
DispatcherServlet.initLocaleResolver(ApplicationContext context)
private void initLocaleResolver(ApplicationContext context) {
try {
this.localeResolver = context.getBean(LOCALE_RESOLVER_BEAN_NAME, LocaleResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.localeResolver);
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.localeResolver.getClass().getSimpleName());
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.localeResolver = getDefaultStrategy(context, LocaleResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No LocaleResolver '" + LOCALE_RESOLVER_BEAN_NAME +
"': using default [" + this.localeResolver.getClass().getSimpleName() + "]");
}
}
}
从ApplicationContext中获取所有类型为LocaleResolver的bean并且设置到localeResolver。出现异常调用getDefaultStrategies获取LocaleResolver。LocaleResolver用于处理国际化和不同区域的语言。
DispatcherServlet.initThemeResolver(ApplicationContext context)
private void initThemeResolver(ApplicationContext context) {
try {
this.themeResolver = context.getBean(THEME_RESOLVER_BEAN_NAME, ThemeResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.themeResolver);
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.themeResolver.getClass().getSimpleName());
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.themeResolver = getDefaultStrategy(context, ThemeResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No ThemeResolver '" + THEME_RESOLVER_BEAN_NAME +
"': using default [" + this.themeResolver.getClass().getSimpleName() + "]");
}
}
}
从ApplicationContext中获取所有类型为ThemeResolver的bean并且设置到themeResolver。出现异常调用getDefaultStrategies获取ThemeResolver。ThemeResolver用于解析主题。
DispatcherServlet.initHandlerMappings(ApplicationContext context)
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
}
// Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerMappings declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
for (HandlerMapping mapping : this.handlerMappings) {
if (mapping.usesPathPatterns()) {
this.parseRequestPath = true;
break;
}
}
}
1、如果detectAllHandlerMappings为true，表示获取所有的HandlerMapping类型的bean，调用BeanFactoryUtils.beansOfTypeIncludingAncestors从ApplicationContext中获取所有类型为HandlerMapping（父类）的bean且按照Order接口排序。否则从ApplicationContext中获取所有类型为HandlerMapping的bean并且设置到handlerMappings。
2、如果handlerMappings为null，调用getDefaultStrategies获取HandlerMapping
3、遍历handlerMappings，如果又HandlerMapping.usesPathPatterns()为true，表示自动使用路径匹配。则设置parseRequestPath为true，退出循环。
HandlerMapping用于将requests映射成处理器。
DispatcherServlet.initHandlerAdapters(ApplicationContext context)
private void initHandlerAdapters(ApplicationContext context) {
this.handlerAdapters = null;
if (this.detectAllHandlerAdapters) {
// Find all HandlerAdapters in the ApplicationContext, including ancestor contexts.
Map<String, HandlerAdapter> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerAdapters = new ArrayList<>(matchingBeans.values());
// We keep HandlerAdapters in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerAdapters);
}
}
else {
try {
HandlerAdapter ha = context.getBean(HANDLER_ADAPTER_BEAN_NAME, HandlerAdapter.class);
this.handlerAdapters = Collections.singletonList(ha);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerAdapter later.
}
}
// Ensure we have at least some HandlerAdapters, by registering
// default HandlerAdapters if no other adapters are found.
if (this.handlerAdapters == null) {
this.handlerAdapters = getDefaultStrategies(context, HandlerAdapter.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerAdapters declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
}
1、如果detectAllHandlerAdapters为true，表示获取所有的HandlerAdapter类型的bean，调用BeanFactoryUtils.beansOfTypeIncludingAncestors从ApplicationContext中获取所有类型为HandlerAdapter（父类）的bean且按照Order接口排序。否则从ApplicationContext中获取所有类型为HandlerAdapter的bean并且设置到handlerAdapters。
2、如果handlerAdapters为null，调用getDefaultStrategies获取HandlerAdapter
HandlerAdapter是MVC框架SPI，允许核心MVC工作流的参数化。
DispatcherServlet.initHandlerExceptionResolvers(ApplicationContext context)
private void initHandlerExceptionResolvers(ApplicationContext context) {
this.handlerExceptionResolvers = null;
if (this.detectAllHandlerExceptionResolvers) {
// Find all HandlerExceptionResolvers in the ApplicationContext, including ancestor contexts.
Map<String, HandlerExceptionResolver> matchingBeans = BeanFactoryUtils
.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerExceptionResolvers = new ArrayList<>(matchingBeans.values());
// We keep HandlerExceptionResolvers in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers);
}
}
else {
try {
HandlerExceptionResolver her =
context.getBean(HANDLER_EXCEPTION_RESOLVER_BEAN_NAME, HandlerExceptionResolver.class);
this.handlerExceptionResolvers = Collections.singletonList(her);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, no HandlerExceptionResolver is fine too.
}
}
// Ensure we have at least some HandlerExceptionResolvers, by registering
// default HandlerExceptionResolvers if no other resolvers are found.
if (this.handlerExceptionResolvers == null) {
this.handlerExceptionResolvers = getDefaultStrategies(context, HandlerExceptionResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No HandlerExceptionResolvers declared in servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
}
1、如果detectAllHandlerExceptionResolvers为true，表示获取所有的HandlerExceptionResolver类型的bean，调用BeanFactoryUtils.beansOfTypeIncludingAncestors从ApplicationContext中获取所有类型为HandlerExceptionResolver（父类）的bean且按照Order接口排序。否则从ApplicationContext中获取所有类型为HandlerExceptionResolver的bean并且设置到handlerExceptionResolvers。
2、如果handlerExceptionResolvers为null，调用getDefaultStrategies获取HandlerExceptionResolver
HandlerExceptionResolver处理执行请求出现的异常，通常映射成错误视图。
DispatcherServlet.initRequestToViewNameTranslator(ApplicationContext context)
private void initRequestToViewNameTranslator(ApplicationContext context) {
try {
this.viewNameTranslator =
context.getBean(REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME, RequestToViewNameTranslator.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.viewNameTranslator.getClass().getSimpleName());
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.viewNameTranslator);
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.viewNameTranslator = getDefaultStrategy(context, RequestToViewNameTranslator.class);
if (logger.isTraceEnabled()) {
logger.trace("No RequestToViewNameTranslator '" + REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME +
"': using default [" + this.viewNameTranslator.getClass().getSimpleName() + "]");
}
}
}
从ApplicationContext中获取所有类型为RequestToViewNameTranslator的bean并且设置到viewNameTranslator。出现异常调用getDefaultStrategies获取RequestToViewNameTranslator。ThemeResolver用于没有显示提供视图名时将request映射成视图名。
DispatcherServlet.initViewResolvers(ApplicationContext context)
private void initViewResolvers(ApplicationContext context) {
this.viewResolvers = null;
if (this.detectAllViewResolvers) {
// Find all ViewResolvers in the ApplicationContext, including ancestor contexts.
Map<String, ViewResolver> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, ViewResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.viewResolvers = new ArrayList<>(matchingBeans.values());
// We keep ViewResolvers in sorted order.
AnnotationAwareOrderComparator.sort(this.viewResolvers);
}
}
else {
try {
ViewResolver vr = context.getBean(VIEW_RESOLVER_BEAN_NAME, ViewResolver.class);
this.viewResolvers = Collections.singletonList(vr);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default ViewResolver later.
}
}
// Ensure we have at least one ViewResolver, by registering
// a default ViewResolver if no other resolvers are found.
if (this.viewResolvers == null) {
this.viewResolvers = getDefaultStrategies(context, ViewResolver.class);
if (logger.isTraceEnabled()) {
logger.trace("No ViewResolvers declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
}
1、如果detectAllViewResolvers为true，表示获取所有的ViewResolver类型的bean，调用BeanFactoryUtils.beansOfTypeIncludingAncestors从ApplicationContext中获取所有类型为ViewResolver（父类）的bean且按照Order接口排序。否则从ApplicationContext中获取所有类型为ViewResolver的bean并且设置到viewResolvers。
2、如果viewResolvers为null，调用getDefaultStrategies获取ViewResolver
ViewResolver是视图解析器，用于将视图名解析成视图。
DispatcherServlet.initFlashMapManager(ApplicationContext context)
private void initFlashMapManager(ApplicationContext context) {
try {
this.flashMapManager = context.getBean(FLASH_MAP_MANAGER_BEAN_NAME, FlashMapManager.class);
if (logger.isTraceEnabled()) {
logger.trace("Detected " + this.flashMapManager.getClass().getSimpleName());
}
else if (logger.isDebugEnabled()) {
logger.debug("Detected " + this.flashMapManager);
}
}
catch (NoSuchBeanDefinitionException ex) {
// We need to use the default.
this.flashMapManager = getDefaultStrategy(context, FlashMapManager.class);
if (logger.isTraceEnabled()) {
logger.trace("No FlashMapManager '" + FLASH_MAP_MANAGER_BEAN_NAME +
"': using default [" + this.flashMapManager.getClass().getSimpleName() + "]");
}
}
}
从ApplicationContext中获取所有类型为FlashMapManager的bean并且设置到flashMapManager。出现异常调用getDefaultStrategies获取FlashMapManager。FlashMapManager用于用于检索和保存FlashMap实例。
DispatcherServlet.getDefaultStrategy(ApplicationContext context, Class
protected <T> T getDefaultStrategy(ApplicationContext context, Class<T> strategyInterface) {
List<T> strategies = getDefaultStrategies(context, strategyInterface);
if (strategies.size() != 1) {
throw new BeanInitializationException(
"DispatcherServlet needs exactly 1 strategy for interface [" + strategyInterface.getName() + "]");
}
return strategies.get(0);
}
DispatcherServlet.getDefaultStrategies(ApplicationContext context, Class
protected <T> List<T> getDefaultStrategies(ApplicationContext context, Class<T> strategyInterface) {
if (defaultStrategies == null) {
try {
// Load default strategy implementations from properties file.
// This is currently strictly internal and not meant to be customized
// by application developers.
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class); // private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties";
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
catch (IOException ex) {
throw new IllegalStateException("Could not load '" + DEFAULT_STRATEGIES_PATH + "': " + ex.getMessage());
}
}
String key = strategyInterface.getName();
String value = defaultStrategies.getProperty(key);
if (value != null) {
String[] classNames = StringUtils.commaDelimitedListToStringArray(value);
List<T> strategies = new ArrayList<>(classNames.length);
for (String className : classNames) {
try {
Class<?> clazz = ClassUtils.forName(className, DispatcherServlet.class.getClassLoader());
Object strategy = createDefaultStrategy(context, clazz);
strategies.add((T) strategy);
}
catch (ClassNotFoundException ex) {
throw new BeanInitializationException(
"Could not find DispatcherServlet's default strategy class [" + className +
"] for interface [" + key + "]", ex);
}
catch (LinkageError err) {
throw new BeanInitializationException(
"Unresolvable class definition for DispatcherServlet's default strategy class [" +
className + "] for interface [" + key + "]", err);
}
}
return strategies;
}
else {
return Collections.emptyList();
}
}
1、如果defaultStrategies为null，加载类路径下DispatcherServlet.properties文件，如webmvc项目下resources/org/springframework/web/servlet/DispatcherServlet.properties
2、defaultStrategies获取strategyInterface.getName()为key的值value
3、如果value不为null，按照,分割后遍历调用ClassUtils.forName构建Class，调用createDefaultStrategy创建bean并加到strategies List中返回
webmvc项目下resources/org/springframework/web/servlet/DispatcherServlet.properties
# Default implementation classes for DispatcherServlet's strategy interfaces.
# Used as fallback when no matching beans are found in the DispatcherServlet context.
# Not meant to be customized by application developers.
org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver
org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver
org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping,\
org.springframework.web.servlet.function.support.RouterFunctionMapping
org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter,\
org.springframework.web.servlet.function.support.HandlerFunctionAdapter
org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\
org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver
org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator
org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver
org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager
