EDIT

Using slashes, double slashes, back slashes in URLs has security implications (see CVE-2007-0450). More recent spring-security releases (e.g. >4.2.18.RELEASE) therefore reject urls like these here:

http://cdmserver.org/registrationDTO/identifier/http://testbank.org/100001
http://cdmserver.org/registrationDTO/identifier/http%3A%2F%2Ftestbank.org%2F100001

The apache configuration also needs a special security configuration to allow encoded slashes (see also #7563)

#
# NOTE: AllowEncodedSlashes is off per default to prevent possible security vulnerabilities.
#       To allow the cdmserver resolving http identifiers via HTTP GET requests it is required to
#       allow encoded slashes. See https://dev.e-taxonomy.eu/redmine/issues/7563
#
AllowEncodedSlashes On

We should completely abstain from using slashes or double slashed in the requests to the RegistrationDTOController by introducing according query parameters instead