How to handle a PSQLException in java?

Question

I have a unique constraint on one of my entities and whenever I get a PSQLException which occurs whenever that constraint is violated, I want to respond with a bad request.

Answer 1

You might as well register an exception handler for that wrapped exception (that @radek mentioned) directly.

In your case that's:

@ExceptionHandler(DataIntegrityViolationException::class)
protected fun handleDataIntegrityException(ex: DataIntegrityViolationException, request: WebRequest) : ResponseEntity{
    return ResponseEntity.badRequest().body(someBodyHere)
}

The error is converted within convertHibernateAccessException in org.springframework.orm.jpa.vendorHibernateJpaDialect, which has already processed away from PSQL. You can add a breakpoint there and follow the stacktrace.

There is a lot of proxy'ing happening under the hood, but the takeaway is that there is always a readable, expressive Exception to use directly.