Spring web环境容器启动流程

1.初始化入口

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

public class ContextLoaderListener extends ContextLoader implements ServletContextListener 

通过实现ServletContextListener 在ServletContext初始化完成的时候，容器开始初始化。

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

2.创建WebApplicationContext实例

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

1.从contextClass参数中获取自定义的类

String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);

2.如果没有自定义则获取默认的类

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

我们看defaultStrategies初始化

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";

我们看ContextLoader.properties文件中的信息

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

总结：默认创建的是XmlWebApplicationContext实例

3.配置和刷新上下文

configureAndRefreshWebApplicationContext(cwac, servletContext);

1.从ServletContext中获取配置文件路径

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

public static final String CONFIG_LOCATION_PARAM = "contextConfigLocation";

2.创建环境对象

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

@Overrideprotected ConfigurableEnvironment createEnvironment() {   return new StandardServletEnvironment();}

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

3.定制上下文初始化

customizeContext(sc, wac);

获取ApplicationContextInitializer的实现类

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";

进行初始化

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

4.刷新容器

wac.refresh();

刷新的流程是固定的（模版模式）。只是刷新流程中有些方法子类是可以覆盖的。

1.重写了postProcessBeanFactory方法

@Overrideprotected 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);}

2.重写了onRefresh方法

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