如何在我的Spring应用程序中获得firebase的Oauth 2.0访问令牌

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseAuthException;
import com.google.firebase.auth.FirebaseToken;

public class FirebaseAuthService {
    public String getAccessToken(String firebaseIdToken) throws FirebaseAuthException {
        FirebaseToken decodedToken = FirebaseAuth.getInstance().verifyIdToken(firebaseIdToken);
        return decodedToken.getAccessToken();
    }
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {
    @Autowired
    private FirebaseAuthService firebaseAuthService;

    @PostMapping("/getAccessToken")
    public String getAccessToken(@RequestParam("firebaseIdToken") String firebaseIdToken) {
        try {
            String accessToken = firebaseAuthService.getAccessToken(firebaseIdToken);
            return accessToken;
        } catch (FirebaseAuthException e) {
            // 处理身份验证异常
            return "Error: " + e.getMessage();
        }
    }
}