ExceptionTranslator

Turns a server ErrorResponse into the exception the caller catches, choosing by SQLSTATE.

The distinction the whole hierarchy exists for is drawn here: a unique violation and a deadlock are things an application handles, a syntax error and a missing column are things it fixes, and they arrive as different types so that catch can tell them apart without reading a string. Where a code says nothing useful, UncategorizedDatabaseException carries it through with the server's own message rather than guessing at a category.

The mapping is by SQLSTATE class where PostgreSQL's classes are meaningful and by individual code where they are not — 40001 and 40P01 are both concurrency but want different reasons, and 57014 is a cancelled statement inside a class that is otherwise about the server being in trouble.

One distinction comes before the SQLSTATE, and it is the severity. A FATAL or a PANIC in an open session ends that session, whatever its code says, and goes through translateTermination; a FATAL at login is the server refusing one, and goes through translateRefusal. What reaches translate is always an ERROR.