Mapstruct - How can I inject a spring dependency in the Generated Mapper class

As commented by brettanomyces, the service won't be injected if it is not used in mapping operations other than expressions.

The only way I found to this is :

• Transform my mapper interface into an abstract class
• Inject the service in the abstract class
• Make it protected so the "implementation" of the abstract class has access

I'm using CDI but it should be the samel with Spring :

@Mapper(
        unmappedTargetPolicy = org.mapstruct.ReportingPolicy.IGNORE,
        componentModel = "spring",
        uses = {
            // My other mappers...
        })
public abstract class MyMapper {

    @Autowired
    protected MyService myService;

    @Mappings({
        @Mapping(target="x", expression="java(myservice.findById(obj.getId())))")
    })
    public abstract Dto myMappingMethod(Object obj);

}

It should be possible if you declare Spring as the component model and add a reference to the type of myservice:

@Mapper(componentModel="spring", uses=MyService.class)
public interface MyMapper { ... }

That mechanism is meant for providing access to other mapping methods to be called by generated code, but you should be able to use them in the expression that way, too. Just make sure you use the correct name of the generated field with the service reference.