How to prevent quarkus overwrite packages after compilation?

[MikaelAnderssonWigander]

This is a weird behavior and I don't know if the subject is correct but that is what's happening.

I have a Quarkus application where I use MapStruct to map between objects.
MapStruct is using the annotation processor and generates Impl classes at compile time.

Running on the latest versions of Quarkus and MapStruct and on Java 21 I want to use the jakarta package.

My Mapper class is defined like this:

package org.acme;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.CollectionMappingStrategy;
import org.mapstruct.NullValueCheckStrategy;
import org.mapstruct.NullValuePropertyMappingStrategy;
import org.mapstruct.ReportingPolicy;

@Mapper(componentModel = "cdi", nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE, unmappedTargetPolicy = ReportingPolicy.WARN, collectionMappingStrategy = CollectionMappingStrategy.ADDER_PREFERRED, uses = {
        StringMapper.class }, nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS)
public interface MyMapper {

    @Mapping(target = "surname", source = "lastname")
    PersonDto toResource(Person person);
}

When doing mvn compile it will create this Impl class:

package org.acme;

import jakarta.enterprise.context.ApplicationScoped;
import jakarta.inject.Inject;
import javax.annotation.processing.Generated;

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2025-09-11T12:37:38+0200",
    comments = "version: 1.6.3, compiler: javac, environment: Java 21.0.8 (Oracle Corporation)"
)
@ApplicationScoped
public class MyMapperImpl implements MyMapper {

    @Inject
    private StringMapper stringMapper;

    @Override
    public PersonDto toResource(Person person) {
        if ( person == null ) {
            return null;
        }

        PersonDto personDto = new PersonDto();

        if ( person.getLastname() != null ) {
            personDto.setSurname( stringMapper.map( person.getLastname() ) );
        }
        if ( person.getFirstname() != null ) {
            personDto.setFirstname( stringMapper.map( person.getFirstname() ) );
        }

        return personDto;
    }
}

When then running it using the quarkus:dev or thru vscode Quarkus extension, it will compile again but now the
@Inject is now dependent on the javax package.

What the?

package org.acme;

import jakarta.enterprise.context.ApplicationScoped;
import javax.annotation.processing.Generated;
import javax.inject.Inject;

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2025-09-11T12:43:48+0200",
    comments = "version: 1.6.3, compiler: javac, environment: Java 21.0.8 (Oracle Corporation)"
)
@ApplicationScoped
public class MyMapperImpl implements MyMapper {

    @Inject
    private StringMapper stringMapper;

    @Override
    public PersonDto toResource(Person person) {
        if ( person == null ) {
            return null;
        }

        PersonDto personDto = new PersonDto();

        if ( person.getLastname() != null ) {
            personDto.setSurname( stringMapper.map( person.getLastname() ) );
        }
        if ( person.getFirstname() != null ) {
            personDto.setFirstname( stringMapper.map( person.getFirstname() ) );
        }

        return personDto;
    }
}

Something is wrong here and I don't know what to do to fix this.

Here's a small reproducer:
https://github.com/MikaelAnderssonWigander/code-with-quarkus

[MikaelAnderssonWigander]

In my original repo it creates this error bit not in this small reproducer…

java.lang.RuntimeException: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
        [error]: Build step io.quarkus.arc.deployment.ArcProcessor#generateResources threw an exception: jakarta.enterprise.inject.spi.DeploymentException: java.lang.IllegalStateException: @javax.inject.Inject declared on dts.service.mappers.IndividualExtendedMapperImpl.stringMapper, use @jakarta.inject.Inject instead

[MikaelAnderssonWigander]

I can circumvent this by telling the mapper to use "jakarta-cdi" instead.