通过 ServletContext 获取 WebApplicationContext

在视图或者 struts 中通过 ServletContext 获取 WebApplicationContext，三个方法如下，英文很简单我就不用再翻译了：

• getRequiredWebApplicationContext

  public static WebApplicationContext getRequiredWebApplicationContext(ServletContext sc)                                                              throws IllegalStateException

  Find the root WebApplicationContext for this web application, which is typically loaded via ContextLoaderListener.

  Will rethrow an exception that happened on root context startup, to differentiate between a failed context startup and no context at all.

  Parameters:

  sc - ServletContext to find the web application context for

  Returns:

  the root WebApplicationContext for this web app

  Throws:

  IllegalStateException - if the root WebApplicationContext could not be found

  See Also:

  WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE

• getWebApplicationContext

  public static WebApplicationContext getWebApplicationContext(ServletContext sc)

  Find the root WebApplicationContext for this web application, which is typically loaded via ContextLoaderListener.

  Will rethrow an exception that happened on root context startup, to differentiate between a failed context startup and no context at all.

  Parameters:

  sc - ServletContext to find the web application context for

  Returns:

  the root WebApplicationContext for this web app, or null if none

  See Also:

  WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE

• getWebApplicationContext

  public static WebApplicationContext getWebApplicationContext(ServletContext sc,                                             String attrName)

  Find a custom WebApplicationContext for this web application.

  Parameters:

  sc - ServletContext to find the web application context for

  attrName - the name of the ServletContext attribute to look for

  Returns:

  the desired WebApplicationContext for this web app, or null if none