AuthenticationResource.java

@Path("auth")
public class AuthenticationResource {

    @Inject
    private AuthSession authSession;

    @POST
    @Consumes("application/x-www-form-urlencoded")
    public Response login(@FormParam("login") String login, @FormParam("password") String password) {

        //If user already logged, then get it token
        Optional<String> key = authSession.getToken(login, password);
        if (key.isPresent()) {
            return Response.ok(key.get()).build();
        }

        //Validade login and password on data source
        if (!authSession.getDataSource().containsKey(login)
                || !authSession.getDataSource()
                        .get(login)
                        .getPassword()
                        .equals(password)) {
            return Response.status(Response.Status.UNAUTHORIZED).build();
        }

        String token = TokenUtils.generateToken();
        //Persist the information of authentication on AuthSession
        authSession.putAuthenticated(token, new Auth(login, password, new Date()));
        return Response.ok(token).build();

    }

    @HEAD
    @Path("/{token}")
    public Response checkAuthentication(@PathParam("token") String token) {

        if (authSession.getAuthenticated().containsKey(token)) {

            return Response.ok().build();

        }

        return Response.status(Response.Status.UNAUTHORIZED).build();

    }

}