While a successful lock will return valid XML, I have seen circumstances where error messages are not wrapped in a valid XML structure. I don't believe the Subversion server guarantees it will return valid XML in all error cases. If EcliplsRock.dolock():EclipseRock.doLock_svnkit returns invalid XML it can safely be assumed there was a problem locking the file and the error message will be part of the result (but not necessarily parseable with an XML parser.)