Re: [Cppcms-users] How to catch CPPDB errors

[Artyom B. <art...@ya...>]

I would suggest in general...

Not get into situations where you can get a error, or at least if you expect a error catch it.

What kind of errors can happen:

	1. Constrain violation:

	* Check it before from a transaction assuming isolation
	* Catch at specific point - assume that the error is constraint violation.
	2. Deadlock - due to colliding statements - not much to do. Or let 500 response to happen or catch a cppdb error at the root of you app hierarchy main and say (oops)
	3. Connection errors or other stuff - 500 is more than reasonable - or do it what you did in 2

Now about specific errors.

Probably it would be good idea to derive several sub exceptions like:

cppdb::constraint_error
cppdb::deadlock_error  
cppdb::connection_error

Similarly to the current set: http://cppcms.com/sql/cppdb/classcppdb_1_1cppdb__error.html

Maybe some more I can't think about them right now.

But this requires some code writing and what is even more important - updating each backend and probably
the most hard would be ODBC.

Any volunteers?

 
Artyom Beilis
--------------
CppCMS - C++ Web Framework:   http://cppcms.com/
CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/



>________________________________
> From: Marcel Hellwig <ke...@co...>
>To: cpp...@li... 
>Sent: Wednesday, January 23, 2013 2:35 PM
>Subject: [Cppcms-users] How to catch CPPDB errors
> 
>-----BEGIN PGP SIGNED MESSAGE-----
>Hash: SHA1
>
>Hi everyone,
>
>I'd like to know the "correct" way of handling errors in cppdb
>statements.
>If I do something like this:
>  "INSERT INTO ...." << cppdb::exec;
>and there will be an error, a 500 respond will be given to the client.
>Not that nice.
>Next try was to catch the exception:
>
>  try {
>    "INSERT INTO ...." << cppdb::exec;
>  } catch(cppdb::cppdb_error const &e) {
>    //what can we do here?
>  }
>
>Nice try, but cppdb_error has only the method what() and what gives me
>back a char* with the error description. But there could be more than
>one error in that query. That's why there are error codes. But
>unfortunately every sql provider has different error codes.
>Another problem with cppdb error is that the message will be
>localized, so you cannot parse it.
>
>So... what is the right way to do this?
>
>Regards
>-----BEGIN PGP SIGNATURE-----
>Version: GnuPG v1.4.13 (GNU/Linux)
>Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
>
>iQIcBAEBAgAGBQJQ/9kvAAoJEIROXYQnkAHpZPEQAJwW8mdI96vYANq+9Akaf65C
>ykNGxrygD87HMizKQ0EPhH7qS1KuvvjYHL1z+eryEOHcILsRfvbnaHRsCAGlq6Lk
>hMNrCzKeMQpcKkkYqBN4YGHzXMA+slsnQVNRQtpi7QrB3Veeg5M4Unm2tYZJenUH
>HNRM1rIqqih0R2swYTZa9HXVqNkZyC9ssPo5YUtd5KK/qftv5mb5fbUgh5TIoYh6
>2GqTEZJYqamMeLnUjTGkZ2EOnz07KGPlW0/PBrhYdeTIxesHIKQC3flDKvWPX8cL
>CA0N4uTiAg7EF6L8CJ+CsmsEBe1wa6TSncShcqmqImM0K1ZBmFG/e1AThC80biW2
>u/0A2pBfMqxdJFXDBg+/CS3ewu5A9UFX79bT0EfiZm3cLwsrLZ0bYvsC/c/aAG2v
>7UfENgldy+79Rk4nUS6ZQxKbMJRmOxznsMrCrAPZl4es1VcNpfm5Drsvm6VV4sCs
>0KBqN11o8rZMfLj8fWc139PwJjKGqcGW8xRjykhpWpDFwennygTBz0Hqn0BJf9Of
>8nENk0bPoORGtqcgR2hf5Yp4HrM7QBP2+/hTdWNmrur+pr6tnP08U13hcBZtNlur
>swTucg5WVp1GjHAmf9BZozEHhKZAY7sJZvWAZQJrbcfdYywTO9y6hERj/5sS2J2P
>EmlSmccnwf7Slmw7+5n6
>=CiN2
>-----END PGP SIGNATURE-----
>
>------------------------------------------------------------------------------
>Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS,
>MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current
>with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft
>MVPs and experts. ON SALE this month only -- learn more at:
>http://p.sf.net/sfu/learnnow-d2d
>_______________________________________________
>Cppcms-users mailing list
>Cpp...@li...
>https://lists.sourceforge.net/lists/listinfo/cppcms-users
>
>
>