NullPointerException when making call to Spring Data JPA Repository - spring

Question

When I call my API to validate a token for the frontend I am running into an issue when calling my UserDetailsService's loadUserByUsername method. I am able to pass the username to the method but my userRepository fails to execute the findByUsername method, and I am not sure what is going on. I am printing the name out before the call and it is returning the correct username, also a user of that name exists in the DB.
This is what I am getting in the console:
2020-07-09 22:46:55.121 INFO 18048 --- [nio-8080-exec-4] o.s.web.servlet.DispatcherServlet : Completed initialization in 10 ms
2020-07-09 22:46:55.153 INFO 18048 --- [nio-8080-exec-4] c.g.Apollo.security.jwt.JwtFilter : token not presented...
2020-07-09 22:46:55.759 INFO 18048 --- [nio-8080-exec-4] c.g.Apollo.service.UserService : success...
2020-07-09 22:47:10.885 INFO 18048 --- [nio-8080-exec-5] c.g.Apollo.security.jwt.JwtFilter : token not presented...
2020-07-09 22:47:10.898 INFO 18048 --- [nio-8080-exec-5] c.g.A.s.jwt.JwtUserDetailsService : load user... max123
2020-07-09 22:47:10.909 WARN 18048 --- [nio-8080-exec-5] g.e.SimpleDataFetcherExceptionHandler : Exception while fetching data (/verifyToken) : null
java.lang.NullPointerException: null
at com.**.Apollo.security.jwt.JwtUserDetailsService.loadUserByUsername(JwtUserDetailsService.java:23) ~[classes/:na]
at com.**.Apollo.service.UserService.verifyToken(UserService.java:173) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at io.leangen.graphql.metadata.execution.SingletonMethodInvoker.execute(SingletonMethodInvoker.java:21) ~[spqr-0.9.9.jar:na]
The UserRepository method works just fine when I login a user but fails here.
JwtUserDetailsService, this is called from the verifyToken method:
#Slf4j
#Service
public class JwtUserDetailsService implements UserDetailsService {
private UserRepository userRepository;
#Override
public UserDetails loadUserByUsername(String username) {
log.info("load user... {}", username);
Optional<User> user = userRepository.findByUsername(username);
log.info("after");
if (user.isPresent()) {
log.info("user:: {}", user.get().getUsername());
return getJwtUser(user.get());
} else {
log.info("user not found");
return null;
}
}
public JwtUser getJwtUser(User user) {
return new JwtUser(
user.getId(),
user.getUsername(),
user.getFirstName(),
user.getLastName(),
user.getEmail(),
user.getPassword(),
List.of(new SimpleGrantedAuthority(user.getRole().getRoleName().name())),
user.getEnabled(),
null
);
}
UserRepository:
#Repository
public interface UserRepository extends JpaRepository<User, Long> {
Optional<User> findByUsername(String username);
boolean existsByUsername(String username);
Optional<User> findByToken(String token);
}
UserSerice, this is what is exposed to the frontend:
#GraphQLQuery
public User verifyToken(String token) {
Optional<User> optionalUser = userRepository.findByToken(token);
if(optionalUser.isPresent()) {
UserDetails userDetails = jwtUserDetailsService.loadUserByUsername(optionalUser.get().getUsername());
if(jwtTokenUtil.isTokenValid(token, userDetails)) {
return optionalUser.get();
}
}
return null;
}

Answer 1

It is throwing a NullPointerException because the userRepository in JwtUserDetailsService was not injected and is null.
Create a constructor like the following:
public JwtUserDetailsService(UserRepository userRepository) {
this.userRepository = userRepository;
}

Answer 2

You need to add #Autowired in class JwtUserDetailsService
#Autowired
private UserRepository userRepository;

Answer 3

It seems that your UserRepository dependency is not getting injected in JwtUserDetailsService as you did not autowire it.
You can do the following:
Autowire the dependency using the constructor injection which is the recommended way:
private final UserRepository userRepository;
public JwtUserDetailsService(UserRepository userRepository) {
this.userRepository = userRepository;
}
It is not recommended to autowire your private members, checkout this post
As you are already using project Lombok, more elegant way to do it instead of writing a constructor would be just annotate your class with #RequiredArgsConstructor.
#Slf4j
#RequiredArgsConstructor
#Service
public class JwtUserDetailsService implements UserDetailsService {
private final UserRepository userRepository;
..
}
Here Project lombok will generate a constructor for you which will take care of the dependency injection.