我有一个Spring Boot REST应用程序，它依赖于Firebase中完成的身份验证。在客户端，Firebase生成令牌，借此在Spring
Boot中，我需要验证uid。但是我注意到代码处于回调模式，因此如何实现Spring Boot函数，使其可以完成任务？

    @RequestMapping(value = "/api/restCall", method = RequestMethod.POST, consumes = "application/json", produces = "application/json")
    public Object restCall(@RequestBody Parameters requestBody) throws Exception {

    // idToken comes from the client app (shown above)
        String idToken = requestBody.getToken();

        Task<FirebaseToken> task = FirebaseAuth.getInstance().verifyIdToken(idToken)
            .addOnSuccessListener(new OnSuccessListener<FirebaseToken>() {
                @Override
                public void onSuccess(FirebaseToken decodedToken) {
                    String uid = decodedToken.getUid();
                    // process the code here
                }
        }); 
        // how do I return here, since the code is in the onSuccess?
        // do I return as a DeferredResult?

    }