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Re: Handling DB Unique Constraints
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Re: Handling DB Unique Constraints


On Nov 29, 2009, at 6:01 PM, Ramsey Lee Gurley wrote:


On Nov 24, 2009, at 5:21 PM, Chuck Hill wrote:


On Nov 24, 2009, at 2:17 PM, Anjo Krank wrote:

Not really sure of the messages can be useful, tough, as they use the name of the constraint:

ERROR:  duplicate key value violates unique constraint "bb"

and not the key (postgres). So the end user probably won't know about this. But it may still be better than a real exception.

Run the constraint name + entity name through the "validation exception to nice message" part of Wonder.

e.g.
LoginUser.uniqueUserName = "You have already registered under this user name."

Where uniqueUserName is the constraint name.


Chuck

That'd be awesome on 5.4. EOEntity.indexNamed(foo). 

Except that is not completely implemented.  Maybe in 5.5.


If only I could get an index name... Look at what MySQL returns for a table with a two column unique index:

Yet another reason to not use MySQLToy. :-)

EvaluateExpression failed: <com.webobjects.jdbcadaptor._MySQLPlugIn $MySQLExpression: "INSERT INTO Parent(parentLastName, id, parentName) VALUES (?, ?, ?)" withBindings: 1:"bil- ly"(parentLastName), 2:9(id), 3:"blanks"(parentName)>:
Next exception:SQL State:23000 -- error code: 1062 -- msg: Duplicate entry 'blanks-bil-ly' for key 2

What a disaster... Even if I wanted to parse that to construct an error message, I don't get all the keys that are required by the unique constraint. :-/

The constraint name is what you really want. Maybe you can dig down into the SQLException and extract it. Every database is different. Some are more different than others.


Anyway, I do have a question related to this: Is it possible to get a handle to the eo in there? I can't find it in the db context or the throwable. Right now, the best I can do is throw a

ERXValidationFactory.defaultFactory().createCustomException(null, "UniqueConstraintException");

and return a message like

"Could not save your changes: The value was not unique."

I suppose that's better than crashing, but it's not exactly helpful either. Perhaps I could reconstruct the object in a disposable ec from the failed AdaptorOperation and pass that 'clone' object to the validation factory? Or is that asking for trouble? If I could just get "Parent.parentName.UniqueConstraintException" I could at least make a reasonable assumption about the unique constraint in some/ most cases.


You can get the exact EO if the constraint is not deferred. If it is deferred, you are out of luck. You can match up the table name to the entity name (give or take some inheritance quirks).


Chuck

--
Chuck Hill             Senior Consultant / VP Development

Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems.
http://www.global-village.net/products/practical_webobjects







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References: 


 >Handeling DB Unique Constraints (From: David Avendasora <email@hidden>)


 >Re: Handeling DB Unique Constraints (From: Chuck Hill <email@hidden>)


 >Re: Handeling DB Unique Constraints (From: Anjo Krank <email@hidden>)


 >Re: Handeling DB Unique Constraints (From: Anjo Krank <email@hidden>)


 >Re: Handeling DB Unique Constraints (From: Chuck Hill <email@hidden>)


 >Re: Handling DB Unique Constraints (From: Ramsey Lee Gurley <email@hidden>)























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