JwtFilter.java

@Component
public class JwtFilter extends OncePerRequestFilter {
	
	@Autowired 
	private UserRepository userRepository; 
	
	@Autowired
    private JWTUtils jwtUtils;

	@Override
	    protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException {

	        String authorizationHeader = httpServletRequest.getHeader("Authorization");

	        String token = null;
	        String userName = null;

	        if (authorizationHeader != null && authorizationHeader.startsWith("Bearer ")) {
	            token = authorizationHeader.substring(7);
	            userName = jwtUtils.extractUsername(token);
	        }

	        if (userName != null && SecurityContextHolder.getContext().getAuthentication() == null) {

	            UserDetails userDetails = userRepository.findUserByUsername(userName)
	            							.orElseThrow(() -> new UsernameNotFoundException("User not present"));;

	            if (jwtUtils.validateToken(token, userDetails)) {

	                UsernamePasswordAuthenticationToken usernamePasswordAuthenticationToken =
	                        new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());
	                usernamePasswordAuthenticationToken
	                        .setDetails(new WebAuthenticationDetailsSource().buildDetails(httpServletRequest));
	                SecurityContextHolder.getContext().setAuthentication(usernamePasswordAuthenticationToken);
	            }
	        }
	        filterChain.doFilter(httpServletRequest, httpServletResponse);
	    }
	}

Hi !

I found a reference to this class on https://medium.com/javarevisited/spring-security-jwt-authentication-in-detail-bb98b5055b50

I just wanted to give you some advices / correction suggestions :

1. Your component is a filter that trigger at every request. The fact that it is in charge of using UserRepository bean will lead to a problem --> even with a valid token, a DB request ( or rest call to your authentication server depending ) will be made.

You should consider to include Spring authorities in your JWT token as a claim. Doing it will allow you to remove UserRepo from your filter, avoid those overkill DB request ( or network communication ).
You'll be able to construct your Authentication only with the token and rely on the signature to certify data.

Leaving this point aside, your article is very good. Thank you for this good read :)