JWTAuthenticationFilter.java

public class JWTAuthenticationFilter extends UsernamePasswordAuthenticationFilter {

    private AuthenticationManager authenticationManager;

    public JWTAuthenticationFilter(AuthenticationManager authenticationManager) {
        this.authenticationManager = authenticationManager;
    }

    @Override
    public Authentication attemptAuthentication(HttpServletRequest req,
                                                HttpServletResponse res) throws AuthenticationException {
        try {
            Developer creds = new ObjectMapper()
                    .readValue(req.getInputStream(), Developer.class);

            return authenticationManager.authenticate(
                    new UsernamePasswordAuthenticationToken(
                            creds.getUsername(),
                            creds.getPassword(),
                            new ArrayList<>())
            );
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    protected void successfulAuthentication(HttpServletRequest req,
                                            HttpServletResponse res,
                                            FilterChain chain,
                                            Authentication auth) throws IOException, ServletException {

        String token = Jwts.builder()
                .setSubject(((User) auth.getPrincipal()).getUsername())
                .setExpiration(new Date(System.currentTimeMillis() + EXPIRATION_TIME))
                .signWith(SignatureAlgorithm.HS512, SECRET.getBytes())
                .compact();
        res.addHeader(HEADER_STRING, TOKEN_PREFIX + token);
    }
}