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3. initHandlerAdapters
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");
}
}
}
和initHandlerMapping一样，我们直接进入到getDefaultStrategies当中。
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);
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();
}
}
其实这里的创建方式和initHandlerMapping方法是一样的，也是同样的拿到HandlerAdapter的全类名之后，去DispatcherServlet.properties中找到对应的类型然后去实例化。
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
HttpRequestHandlerAdapter是http请求处理器适配器，实现了org.springframework.web.HttpRequestHandler， 接口的Bean通过此适配器进行适配、执行。HttpRequestHandlerAdapter作为HTTP请求处理器适配器仅仅支持对HTTP请求处理器的适配。它简单的将HTTP请求对象和响应对象传递给HTTP请求处理器的实现，它并不需要返回值。它主要应用在基于HTTP的远程调用的实现上。SimpleControllerHandlerAdapter是简单控制器处理器适配器，这个实现类将HTTP请求适配到一个控制器的实现进行处理。这里控制器的实现是一个简单的控制器接口的实现。RequestMappingHandlerAdapter实现了HandlerAdapter接口，顾名思义，表示handler的adapter，这里的handler指的是Spring处理具体请求的某个Controller的方法，也就是说HandlerAdapter指的是将当前请求适配到某个Handler的处理器。RequestMappingHandlerAdapter是HandlerAdapter的一个具体实现，主要用于将某个请求适配给@RequestMapping类型的Handler处理。- 至于
HandlerFunctionAdapter是有关于函数式接口的。
自然，我们这里使用的就是RequestMappingHandlerAdapter，同样的，他也实现了InitializingBean接口，在创建的时候也会调用afterPropertiesSet方法。
public void afterPropertiesSet() {
this.initControllerAdviceCache();
List handlers;
if (this.argumentResolvers == null) {
handlers = this.getDefaultArgumentResolvers();
this.argumentResolvers = (new HandlerMethodArgumentResolverComposite()).addResolvers(handlers);
}
if (this.initBinderArgumentResolvers == null) {
handlers = this.getDefaultInitBinderArgumentResolvers();
this.initBinderArgumentResolvers = (new HandlerMethodArgumentResolverComposite()).addResolvers(handlers);
}
if (this.returnValueHandlers == null) {
handlers = this.getDefaultReturnValueHandlers();
this.returnValueHandlers = (new HandlerMethodReturnValueHandlerComposite()).addHandlers(handlers);
}
}
其实就是为SpringMVC接受请求处理的对象准备参数，返回值，初始化绑定参数处理器列表。准备完成之后，HandlerAdapter创建完成，initHandlerAdapters结束。
4. initViewResolvers
其实看完前面两个，这个大致也知道了
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); // <--看这里
if (logger.isTraceEnabled()) {
logger.trace("No ViewResolvers declared for servlet '" + getServletName() +
"': using default strategies from DispatcherServlet.properties");
}
}
}
同样是getDefaultStrategies方法，也是同样的步骤，也是同样的拿到ViewResolver的全类名之后，去DispatcherServlet.properties中找到对应的类型然后去实例化。
如果没有在 BeanFactory 中为此命名空间定义 ViewResolver bean，我们默认为 InternalResourceViewResolver。
