1.初始化入口

<listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

public class ContextLoaderListener extends ContextLoader implements ServletContextListener 

通過實現ServletContextListener 在ServletContext初始化完成的時候，容器開始初始化。

/**
 * Initialize the root web application context.
 
 */
@Override
public void contextInitialized(ServletContextEvent event) {
   initWebApplicationContext(event.getServletContext());
}

2.建立WebApplicationContext例項

if (this.context == null) {
   this.context = createWebApplicationContext(servletContext);
}

1.從contextClass引數中獲取自定義的類

String contextClassName 
 
= servletContext.getInitParameter(CONTEXT_CLASS_PARAM);

contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName());

private static final Properties defaultStrategies;
static {
   // Load default strategy implementations from properties file.
 
   // This is currently strictly internal and not meant to be customized
   // by application developers.
try {
      ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class);
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
   catch (IOException ex) {
      throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage());
}
}

/**
 * Name of the class path resource (relative to the ContextLoader class)
 * that defines ContextLoader's default strategy names.
 */
private static final String DEFAULT_STRATEGIES_PATH = "ContextLoader.properties";

org.springframework.web.context.WebApplicationContext=org.springframework.web.context.support.XmlWebApplicationContext

3.配置和重新整理上下文

configureAndRefreshWebApplicationContext(cwac, servletContext);

String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocationParam != null) {
   wac.setConfigLocation(configLocationParam);
}

public static final String CONFIG_LOCATION_PARAM = "contextConfigLocation";

ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
   ((ConfigurableWebEnvironment) env).initPropertySources(sc, null);
}

@Override
protected ConfigurableEnvironment createEnvironment() {
   return new StandardServletEnvironment();
}

@Override
public void initPropertySources(ServletContext servletContext, ServletConfig servletConfig) {
   WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
}

customizeContext(sc, wac);

獲取ApplicationContextInitializer的實現類

List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> initializerClasses =
      determineContextInitializerClasses(sc);

protected List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>>
      determineContextInitializerClasses(ServletContext servletContext) {

   List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> classes =
         new ArrayList<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>>();
String globalClassNames = servletContext.getInitParameter(GLOBAL_INITIALIZER_CLASSES_PARAM);
   if (globalClassNames != null) {
      for (String className : StringUtils.tokenizeToStringArray(globalClassNames, INIT_PARAM_DELIMITERS)) {
         classes.add(loadInitializerClass(className));
}
   }

   String localClassNames = servletContext.getInitParameter(CONTEXT_INITIALIZER_CLASSES_PARAM);
   if (localClassNames != null) {
      for (String className : StringUtils.tokenizeToStringArray(localClassNames, INIT_PARAM_DELIMITERS)) {
         classes.add(loadInitializerClass(className));
}
   }

   return classes;
}

public static final String GLOBAL_INITIALIZER_CLASSES_PARAM = "globalInitializerClasses";

public static final String CONTEXT_INITIALIZER_CLASSES_PARAM = "contextInitializerClasses";

for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) {
   initializer.initialize(wac);
}

4.重新整理容器

wac.refresh();

@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
beanFactory.ignoreDependencyInterface(ServletConfigAware.class);
WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}

@Override
protected void onRefresh() {
   this.themeSource = UiApplicationContextUtils.initThemeSource(this);
}