HHH-18679 throw exception when columnValues is null while addKeyColumn

[anaconda875]

Currently, the code will throw NPE when annotating the id with @Generated(writable = true) WITHOUT sql attribute
This fix is about throwing a dedicated exception instead of NPE as we can not handle any further.

Note: I'm a new contributor, so my code might be bad. Please give me advices/suggestions if the PR is so stupid, I will do my best to fix it. Thank you so much

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https://hibernate.atlassian.net/browse/HHH-18679

[mbladel]

Hey @anaconda874, thank you so much for opening the PR and trying to solve this!

The NPE thrown by Hibernate of course is an issue, and while your idea of validating this case and generating a better error message is definitely on the right track (though I would not create a new exception and just use IdentifierGenerationException), I think we have the tools to actually allow @Generated(writable = true) on an identifier property to work.

I was looking at your issue as well and I've created #9078, with this change we should be able to understand when a generated id is writable and read the value from the persisted entity instead of letting the database generate one.

[anaconda875]

I was looking at your issue as well and I've created #9078, with this change we should be able to understand when a generated id is writable and read the value from the persisted entity instead of letting the database generate one.

Hi @mbladel I did not know about the BeforeExecutionGenerator and @ColumnDefault. I have to find another ticket to practise more

[mbladel]

Don't worry @anaconda875, your contribution is still very much appreciated - and let's see what the others think.

Note: I used @ColumnDefault in the test just for a quick way to have a database-generated value, realistically one would have some sort of trigger / database function generating the identifier value on the fly.

[anaconda875]

Note: I used @ColumnDefault in the test just for a quick way to have a database-generated value, realistically one would have some sort of trigger / database function generating the identifier value on the fly.

Hi @mbladel , may I ask a question? If there are "some sort of trigger / database function generating the identifier", then why we need writable = true?
The document of sql says that Determines if the value currently assigned to the annotated property is included in SQL insert and update statements

[mbladel]

If there are "some sort of trigger / database function generating the identifier", then why we need writable = true

Well, as you said (and the documentation you posted is about the writable flag) the user might choose to persist an entity with a value that was already assigned to the property annotated with @Generated. The same can be true for identifiers, mainly useful for testing where you might want to persist some data with a known id value to deterministically produce a desired outcome.