How do I log com.fasterxml.jackson errors with Quarkus? - json

Question

I use Jackson to check and databind input JSON for a REST API, and I would like to log the error when the input doesn’t match a #Valid constraint.
However, the exceptions are throwned as a Response by the API but do not appear in Quarkus’ logs.
How do I log Jackson’s exceptions ?

Answer 1

One has to create a handler for the Jackson exceptions, e.g. using ExceptionMapper.
The following example catches all exceptions of type JsonProcessingException (finer tuning is obviously possible), logs them as SEVERE (using lombok’s #Log annotation) and returns a 400 Bad Request Response including the message. Note that the function has to be toResponse(Exception).
import javax.ws.rs.core.Response;
import javax.ws.rs.ext.ExceptionMapper;
import javax.ws.rs.ext.Provider;
import com.fasterxml.jackson.core.JsonProcessingException;
import lombok.extern.java.Log;
#Log
#Provider
public class MyJsonProcessingExceptionHandler implements ExceptionMapper<JsonProcessingException> {
#Override
public Response toResponse(JsonProcessingException exception) {
log.severe(exception.getMessage());
return Response.status(Response.Status.BAD_REQUEST).entity(exception.getMessage()).build();
}
}
Do not forget the #Provider annotation so that the Exception handler acts as a filter on the REST API.
In principle other files of the project (including the controller) do not need to be modified, only this class in its own file.