WebHDFS: GETSNAPSHOTDIFF API NPE when param "snapshotname" is given but "oldsnapshotname" is not.

# Bash

# Prerequisite: You will need to create the directory "/snapshot", allowSnapshot() on it, and create a snapshot named "snap3" for it to reach NPE.

$ curl "http://<SERVER>:<PORT>/webhdfs/v1/snaptest/?op=GETSNAPSHOTDIFF&user.name=hdfs&oldsnapshotnameZZZ=snap2&snapshotname=snap3"
# Note that I intentionally typed the wrong parameter name for "oldsnapshotname" above to cause NPE.

{"RemoteException":{"exception":"NullPointerException","javaClassName":"java.lang.NullPointerException","message":null}}


# OR

$ curl "http://<SERVER>:<PORT>/webhdfs/v1/snaptest/?op=GETSNAPSHOTDIFF&user.name=hdfs&oldsnapshotname=&snapshotname=snap3"
# Empty string for oldsnapshotname

{"RemoteException":{"exception":"NullPointerException","javaClassName":"java.lang.NullPointerException","message":null}}


# OR

$ curl "http://<SERVER>:<PORT>/webhdfs/v1/snaptest/?op=GETSNAPSHOTDIFF&user.name=hdfs&snapshotname=snap3"
# Missing param oldsnapshotname, essentially the same as the first case.

{"RemoteException":{"exception":"NullPointerException","javaClassName":"java.lang.NullPointerException","message":null}