Constructor parameters for Mappers

[George Pai]

I am in the middle of converting my code from using Spring field injection to using constructor injection, mainly for testing and mocking purposes.  I am having issues with my mappers though, since MapStruct only seems to use Spring field injection.

Summary

1. Is there a way to define a parameterized constructor for a Mapper
2. Is there a way to use any other Spring injection other than field when using other mappers

Details

This is what I basically have now (minus irrelevant and implicit code)

public class User {
    private Set<Role> roles;
}


public class Role {

    private String name;
}


@Service
public class RoleService {
    public Role getRoleByName(String roleName) { // impl }
}


public class UserViewModel {
    private Set<String> roles;
}


@Mapper(uses = "RoleMapper.class")
public interface UserMapper {
    UserViewModel userToUserViewModel(User user);


    User userViewModelToUser(UserViewModel userViewModel);
}


@Mapper
public abstract class RoleMapper {
    protected RoleService roleService;


    public Role roleNameToRole(String roleName) {
        Role role = roleService.getRoleByName(roleName);
        if (role == null) {
            throw new RuntimeException(MessageFormat.format("Unknown role {0}", roleName));
        }
        return role;
   }


    public String roleToRoleName(Role role) {
        return role == null ? null : role.getName();
    }


    @Autowired
    public void setRoleService(RoleService roleService) {

        this.roleService = roleService;
    }
}

As you can see I am using setter injection for the RoleMapper instead of constructor injection since compilation fails if I try and define a parameterized constructor. So my first question is "Is there a way to define a parameterized constructor for a Mapper?" (my guess is no since even if there were Mappers.getMapper only has a class as a parameter, with no way to send parameters)

The main issue I'm having is that the uses = "RoleMapper.class" (using Spring) generates an @Autowired private RoleMapper roleMapper; in the UserMapperImpl which works fine except that I can't mock that roleService properly.  If I do a UserMapper userMapper = new UserMapperImpl() in my tests I can't inject a RoleMapper and if I use @RunWith(SpringJUnit4ClassRunner.class) to autowire it and inject mocks then, being that it has a singleton scope, it affects other tests that need it not to be mocked.  Ideally what I would want is constructor (or even setter) injection so that I can construct exactly what I need for some tests while leaving the Spring bean alone.

[Andreas Gudian]

Hi George,

Supporting constructor injection is something that is on our agenda, albeit it came up in an issue with component-model "jsr330" in combination with Dagger DI:
https://github.com/mapstruct/mapstruct/issues/571

Would you add a comment that this would also be helpful for Spring, so we don't forget about it?

Thanks,

Andreas

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[George Pai]

Comment added to about Spring DI to the issue below.

[Gunnar Morling]

Am Mittwoch, 28. Oktober 2015 19:55:26 UTC+1 schrieb George Pai:

Comment added to about Spring DI to the issue below.

Thanks! Would you be interested in helping out with implementing this issue?

I suppose as a first step into this direction we could - optionally - generate the default constructor as now *and* a constructor expecting all the dependencies of the mapper. This should help with testing as in your case.