strust2中是如何初始化container并且使其全局单例

strust2中是如何初始化container并且使其全局单例？

StrutsPrepareAndExecuteFilter
   protected PrepareOperations prepare;
    protected ExecuteOperations execute; 
 
Dispatcher dispatcher = init.initDispatcher(config);
      init()
      Container container = init_PreloadConfiguration();
 
 
   private Container init_PreloadConfiguration() {
        Configuration config = configurationManager.getConfiguration();
        Container container = config.getContainer();        boolean reloadi18n = Boolean.valueOf(container.getInstance(String.class, StrutsConstants.STRUTS_I18N_RELOAD));
        LocalizedTextUtil.setReloadBundles(reloadi18n);        return container;
    } 
       Configuration config = configurationManager.getConfiguration();
        Container container = config.getContainer(); 
 
 
  public synchronized Configuration getConfiguration() {
        if (configuration == null) {
            setConfiguration(createConfiguration(defaultFrameworkBeanName));
            try {
                configuration.reloadContainer(getContainerProviders());
            } catch (ConfigurationException e) {
                setConfiguration(null);
                throw new ConfigurationException("Unable to load configuration.", e);
            }
        } else {
            conditionalReload(configuration.getContainer());
        }        return configuration;
    }....
 
 
 
 
 prepare = new PrepareOperations(filterConfig.getServletContext(), dispatcher);
 execute = new ExecuteOperations(filterConfig.getServletContext(), dispatcher);