SpringMVC源码分析（2）DispatcherServlet的初始化

DispatcherServlet的初始化，是在org.springframework.web.context.ContextLoaderListener完成加载后，才开始的。这时候WebApplicationContext（包含DAO,Service等）已经初始完毕。
DispatcherServlet的初始过程主要完成
1.WebApplicationContext父子容器维护
2.初始化Servlet策略
本文主要内容
DispatcherServlet的集成体系

DispatcherServlet初始化过程

1.DispatcherServlet的继承体系




DispatcherServlet是个普通servlet,是访问入口。明白了继承体系，方便梳理初始化模板。

2.DispatcherServlet初始化过程



2.1 init

public final void init() throws ServletException {

// Set bean properties from init parameters.
//将Servlet配置的参数封装到pvs变量中
try {
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader));
initBeanWrapper(bw);//bw就是DispatcherServlet
bw.setPropertyValues(pvs, true);
}

// 让子类实现
initServletBean();

if (logger.isDebugEnabled()) {
logger.debug("Servlet '" + getServletName() + "' configured successfully");
}
}

2.2 initServletBean方法

protected final void initServletBean() throws ServletException {
this.webApplicationContext = initWebApplicationContext();
initFrameworkServlet();//子类可以实现

}

初始化webApplicationContext ；初始化FrameworkServlet
2.3 initWebApplicationContext方法

protected WebApplicationContext initWebApplicationContext() {
WebApplicationContext wac = findWebApplicationContext();
if (wac == null) {
// No fixed context defined for this servlet - create a local one.
WebApplicationContext parent =
WebApplicationContextUtils.getWebApplicationContext(getServletContext());
wac = createWebApplicationContext(parent);
}

if (!this.refreshEventReceived) {
// Apparently not a ConfigurableApplicationContext with refresh support:
// triggering initial onRefresh manually here.
onRefresh(wac);////调用DispatcherServlet.initStrategies入口
}

if (this.publishContext) {
// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
...
}
}

return wac;
}

protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
Class<?> contextClass = getContextClass();
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
wac.setParent(parent);//维护双亲委派
wac.setServletContext(getServletContext());
wac.setServletConfig(getServletConfig());
wac.setNamespace(getNamespace());
wac.setConfigLocation(getContextConfigLocation());
//调用DispatcherServlet.initStrategies入口
wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));
postProcessWebApplicationContext(wac);
wac.refresh();
return wac;
}

private class ContextRefreshListener implements ApplicationListener<ContextRefreshedEvent> {

public void onApplicationEvent(ContextRefreshedEvent event) {
FrameworkServlet.this.onApplicationEvent(event);
}
}

2.5.initStrategies方法

protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
}

初始化9个组件。
初始化组件过程，大体都是先从容器中获取，获取不到，则调用getDefaultStrategy(ApplicationContext context, Class<T> strategyInterface)方法。
默认配置来自DispatcherServlet.properties

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.annotation.DefaultAnnotationHandlerMapping

org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter

org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver,\
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

2.6.initHandlerMappings方法

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<HandlerMapping>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
OrderComparator.sort(this.handlerMappings);
}
}
else {
...
}

}
}

将spring mvc容器中HandlerMapping对象赋给handlerMappings 列表。这些对象都是在标签解析时，自动加载入容器中的。具体<SpringMVC源码分析（1）标签解析>
2.7 initHandlerAdapters方法
与initHandlerMappings思路完全一致。