Returns fresh keys for the given Kerberos principal.
Implementation of this method should make sure the returned keys match the latest content of the keytab file. The result is a newly created copy that can be modified by the caller without modifying the keytab object. The caller should
destroy the result keys after they are used.
Please note that the keytab file can be created after the
KeyTab object is instantiated and its content may change over time. Therefore, an application should call this method only when it needs to use the keys. Any previous result from an earlier invocation could potentially be expired.
If there is any error (say, I/O error or format error) during the reading process of the keytab file, a saved result should be returned. If there is no saved result (say, this is the first time this method is called, or, all previous read attempts failed), an empty array should be returned. This can make sure the result is not drastically changed during the (probably slow) update of the keytab file.
Each time this method is called and the reading of the file succeeds with no exception (say, I/O error or file format error), the result should be saved for
principal. The implementation can also save keys for other principals having keys in the same keytab object if convenient.
Any unsupported key read from the keytab is ignored and not included in the result.
If this keytab is bound to a specific principal, calling this method on another principal will return an empty array.