How to use #ConfigProperty in a MapStruct mapper? - mapstruct

Question

I need a #ConfigProperty in my Mapper.
I cannot inject it, since the Mapper is an interface.
How can I solve this?
#ConfigProperty(name = "limit") // <- Does not work here
int limit;
#Mapping(target = "myTarget", source = "mySource", qualifiedByName = "myLimitMapper")
MyDto toDTO(Entity entity);
#Named(value = "myLimitMapper")
default int mapLimit(int number) {
if (number >= limit) return limit;
else return number;
}

Answer 1

I'm assuming you're using Quarkus, seeing the #ConfigProperty. But you can define an abstract mapper and use the cdi componentModel to let MapStruct create an #ApplicationScoped CDI bean. This is described in the dependency injection section of the MapStruct docs.
E.g. you have 2 classes to map:
public record UserModel(String name, int number) {}
public record UserDto(String name, int number) {}
In which limit is configured in the application.properties as 100.
Your mapper will look like:
#Mapper(componentModel = "cdi")
public abstract class UserMapper {
#ConfigProperty(name = "limit")
int limit;
#Mapping(target = "number", source = "number", qualifiedByName = "myLimitMapper")
abstract UserDto mapToDto(UserModel userModel);
#Named(value = "myLimitMapper")
int mapLimit(int number) {
if (number >= limit) return limit;
else return number;
}
}
You could run this as a #QuarkusTest to verify:
#QuarkusTest
public class LimitTest {
#Inject
UserMapper userMapper;
#Test
public void testMapping() {
UserModel userModel = new UserModel("John", 150);
UserDto userDto = userMapper.mapToDto(userModel);
assertEquals("John", userDto.name());
assertEquals(100, userDto.number());
}
}