Make Injector field final

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Make code less verbose

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Directly throw exceptions from error converters

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>