Working with Spring, Java > 1.8 and Mapstruct 1.4.2.Final.

The mappers generated for Spring ( componentModel = "spring") are implementing an interface, annotated with @Component, so they don't need to be public, they can be package-private by default.

They are meant to be injected by Spring in other classes/services, so the usual client code don't needs to do new MyMapperImpl();

Can you add a way to generate package-private implementations?

In a project, it can be detected by running test using ArchUnit ( this test with fail due to MapStruct generated classes).

ArchRuleDefinition.noClasses()
            .that()
            .haveSimpleNameEndingWith("Impl")
            .should().bePublic()
            .because("Implementations don't need to be public")
            .check(new ClassFileImporter().withImportOption(ImportOption.Predefined.DO_NOT_INCLUDE_TESTS).importPackages("my.nice.pacakge"));