global Exception Handler overrules database transaction handler

Question

I am sort of stuck at a particular funny error in a quarkus REST-service that I am currently developing. My application manages panache entities and I implemented some CRUD operations in a resource controller. I annotated that controller with @Transactional(like the documentation suggest) and for good measure I added a global exception handler which looks roughly like the following snippet:

import jakarta.ws.rs.core.Response;
import org.jboss.resteasy.reactive.server.ServerExceptionMapper;


public class MyExceptionHandler {
    @ServerExceptionMapper
    public Response entityToBig(EntityToBigException e) {
        return Response.status(Response.Status.BAD_REQUEST)
    // ErrorMessage is just a record to hold the message
    .entity(new ErrorMessage("Error", e.getMessage(), Response.Status.BAD_REQUEST.getStatusCode())).build();
    }

   //... other handlers
}

The thing is now, that if I throw a Exception which is handled by my ExceptionHandler class the Status code and message is presented correctly to the end-user but the changes done in the prior request are ALSO committed to the database!

If I throw a Exception that is not handled by my ExceptionHandler class the transaction rollback works just fine...

I could not find any other documentation on this issue so I am quite perplexed on how to solve this/manually tell the transaction manager to rollback my changes.

Answer 1

Ok so the fix is quite simple but very hidden away in the depths of the documentation. From https://quarkus.io/guides/transaction#starting-and-stopping-transactions-defining-your-boundaries we can learn that only RuntimeExceptions will automatically rollback the current transaction context.

So that means if I, who of course tries to develop clean software, define a custom base Exception class for my service which is just a regular checked exception, that exception will NEVER rollback the current Transaction.

The solution to this is pretty simple, take your class that is annotated with @Transactional (as the documentation suggest a REST-Controller) and add the prameter rollbackOn to the decorator.

@ApplicationScoped
@Path("/api/v1/")
@Produces(MediaType.APPLICATION_JSON)
@Tag(name = "CustomerNetwork API", description = "Operations related to customer networks")
@Authenticated
@Transactional(rollbackOn = {EntityToBigException.class})
public class CustomerNetworkController {
 // REST endpoints ...
}

This ensures that the Transaction is rolled back whenever your custom exception or exceptions that inherit your exception are thrown.