@Override
public Authentication attemptAuthentication(HttpServletRequest req, HttpServletResponse res)
        throws AuthenticationException, IOException, ServletException {
    String reqBody = req.getReader().lines().collect(Collectors.joining(System.lineSeparator()));

    // this appears to be empty on angular client calls
    System.out.println(reqBody);

    ObjectMapper objectMapper = new ObjectMapper().configure(Feature.AUTO_CLOSE_SOURCE, true)
            .enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
    AccountCredentials creds = objectMapper.readValue(reqBody, AccountCredentials.class);

    return getAuthenticationManager().authenticate(new UsernamePasswordAuthenticationToken(creds.getUsername(),
                creds.getPassword(), Collections.emptyList()));
}

const user = {
  username: "asdf",
  password: "asdf"
};

// imported from '@angular/http'
const headers = new Headers({
  'Content-Type': 'application/json'
});
const body = JSON.stringify(user);
return this.http
  .put("http://localhost:8080/api/login", body, {headers})
  .toPromise()
  .then(response => response.json().data as User)
  .catch(this.handleError);