Specifies the authentication method.
If the parent element is as-context, the only supported value is USERNAME_PASSWORD.
If the parent element is login-config, specifies the authentication mechanism for the web service endpoint. As a prerequisite to gaining access to any web resources protected by an authorization constraint, a user must be authenticated using the configured mechanism.
login-config (sun-web.xml), as-context (sun-ejb-jar.xml)
none - contains data