record Entity(long id, String firstName, String lastName) {
}

@Mapper
public interface MyMapper {
    @Mapping(target = "id", source = "id")
    Entity fromMap(long id, Map<String, String> fields);
}

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2024-09-06T12:01:59+0300",
    comments = "version: 1.5.5.Final, compiler: IncrementalProcessingEnvironment from gradle-language-java-8.4.jar, environment: Java 17.0.10 (Amazon.com Inc.)"
)
public class MyMapperImpl implements MyMapper {

    @Override
    public Entity fromMap(long id, Map<String, String> fields) {
        if ( fields == null ) {
            return null;
        }

        String firstName = null;
        String lastName = null;
        if ( fields != null ) {
            if ( fields.containsKey( "firstName" ) ) {
                firstName = fields.get( "firstName" );
            }
            if ( fields.containsKey( "lastName" ) ) {
                lastName = fields.get( "lastName" );
            }
        }
        long id1 = 0L;
        id1 = id;

        Entity entity = new Entity( id1, firstName, lastName );

        return entity;
    }
}

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2024-09-06T12:03:23+0300",
    comments = "version: 1.6.0, compiler: IncrementalProcessingEnvironment from gradle-language-java-8.4.jar, environment: Java 17.0.10 (Amazon.com Inc.)"
)
public class MyMapperImpl implements MyMapper {

    @Override
    public Entity fromMap(long id, Map<String, String> fields) {
        if ( fields == null ) {
            return null;
        }

        long id1 = 0L;
        id1 = id;

        String firstName = null;
        String lastName = null;

        Entity entity = new Entity( id1, firstName, lastName );

        return entity;
    }
}

MyMapper.java:14: warning: Unmapped target properties: "firstName, lastName".
    Entity fromMap(long id, Map<String, String> fields);
           ^
1 warning