A. The attribute foo is placed in the application
B. A ServletContextListener registered for that servlet is notified
C. A ServletAttributeListener registered for that servlet is notified
D. An HttpSessionAttributeListener registered for that servlet is notified

A. The init method on a filter is called the first time a servlet mapped to that filter is invoked
B. A filter defined for a servlet must always forward control to the next resource in the filter chain.
C. Filters associated with a named servlet are applied in the order they appear in the web application deployment descriptor file
D. If the init method on a filter throws an UnavailableException， then the container will make no further attempt to execute it