Check zone id

[strehle]

After discussions in #2606

Add null checks to improve robustness in this dao

add more tests to cover all edge cases

https://sonarcloud.io/summary/new_code?id=cloudfoundry-identity-parent&pullRequest=2617

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/186543964

The labels on this github issue will be updated when the story is started.

[klaus-sap]

looks good to me

[strehle]

@swalchemist This is a small refactoring in preparation of a pr from @klaus-sap .

Return now an exception before asking JDBC (or DB) about null for a zone.
EmptyResultDataAccessException("Zone id cannot be null", 1);

[tack-sap]

@strehle currently the methods do not throw EmptyResultDataAccessException, but only ZoneDoesNotExistException. Would this maybe be a better Exception to throw, as this is something the calling classes may already expect?

[strehle]

@strehle currently the methods do not throw EmptyResultDataAccessException, but only ZoneDoesNotExistException. Would this maybe be a better Exception to throw, as this is something the calling classes may already expect?

ok

[tack-sap]

LGTM