Returns the object bound to this session identified by the specified key. If there is no
object bound under the key, {@code null} is returned.
@param key the unique name of the object bound to this session
@return the object bound under the specified {@code key} name or {@code null} if there is
no object bound under that name.
@throws InvalidSessionException if this session has stopped or expired prior to calling
this method.
Returns the object bound to this session identified by the specified key. If there is no object bound under the key, {@code null} is returned.
@param key the unique name of the object bound to this session @return the object bound under the specified {@code key} name or {@code null} if there is no object bound under that name. @throws InvalidSessionException if this session has stopped or expired prior to calling this method.