java.lang.NoClassDefFoundError: com/google/appengine/api/urlfetch/HTTPMethod

Question

I am attempting to verify Google ID tokens with a backend server as per:

https://developers.google.com/identity/sign-in/android/backend-auth

The tokens are initially retrieved by an android app, and are then passed to a backend login server via sockets which attempts verification. As things stand, there is an error thrown at runtime within the GoogleIdTokenVerifier code I am importing.

ServerThread.java:

GoogleIdToken idToken = GoogleAuthenticator.authenticateToken(tokenJson.getToken());

GoogleAuthenticator.java:

import java.io.IOException;
import java.security.GeneralSecurityException;
import java.util.Collections;
import java.util.Properties;

import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.extensions.appengine.http.UrlFetchTransport;

public class GoogleAuthenticator {

    public GoogleAuthenticator(){

    }

    public static Properties prop;

    public static GoogleIdToken authenticateToken(String inputToken) throws IOException{

    final JacksonFactory jacksonFactory = new JacksonFactory();
    prop = new Properties();
    prop.load(GoogleAuthenticator.class.getClassLoader().getResourceAsStream("config.properties"));

    GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(UrlFetchTransport.getDefaultInstance(), jacksonFactory)
            // Specify the CLIENT_ID of the app that accesses the backend:
            .setAudience(Collections.singletonList(prop.getProperty("google.web.client.id")))
            // Or, if multiple clients access the backend:
            //.setAudience(Arrays.asList(CLIENT_ID_1, CLIENT_ID_2, CLIENT_ID_3))
            .build();

        GoogleIdToken idToken;
        try {
            idToken = verifier.verify(inputToken);
            return idToken;
        } catch (GeneralSecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return null;
        }
    }
}

pom.xml

    <dependency>
        <groupId>com.google.api-client</groupId>
        <artifactId>google-api-client</artifactId>
        <version>1.25.0</version>
   </dependency>

   <dependency>
        <groupId>com.google.api-client</groupId>
        <artifactId>google-api-client-appengine</artifactId>
        <version>1.25.0</version>
   </dependency>

I am currently seeing the following stack trace:

Exception in thread "Thread-0" java.lang.NoClassDefFoundError: com/google/appengine/api/urlfetch/HTTPMethod
    at com.google.api.client.extensions.appengine.http.UrlFetchTransport.buildRequest(UrlFetchTransport.java:118)
    at com.google.api.client.extensions.appengine.http.UrlFetchTransport.buildRequest(UrlFetchTransport.java:50)
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:872)
    at com.google.api.client.googleapis.auth.oauth2.GooglePublicKeysManager.refresh(GooglePublicKeysManager.java:172)
    at com.google.api.client.googleapis.auth.oauth2.GooglePublicKeysManager.getPublicKeys(GooglePublicKeysManager.java:140)
    at com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier.verify(GoogleIdTokenVerifier.java:174)
    at com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier.verify(GoogleIdTokenVerifier.java:192)
    at com.omarhegazi.login.GoogleAuthenticator.authenticateToken(GoogleAuthenticator.java:40)
    at com.omarhegazi.login.ServerThread.run(ServerThread.java:45)

It looks like there's no HTTPMethod class available amongst the dependencies. Any thoughts?

UPDATE 1:

Adding the appengine dependency below has made some progress. I now have the following stack trace error:

Exception in thread "Thread-0" com.google.apphosting.api.ApiProxy$CallNotFoundException: The API package 'urlfetch' or call 'Fetch()' was not found.
    at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:98)
    at com.google.appengine.api.urlfetch.URLFetchServiceImpl.fetch(URLFetchServiceImpl.java:37)
    at com.google.api.client.extensions.appengine.http.UrlFetchRequest.execute(UrlFetchRequest.java:74)
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:981)
    at com.google.api.client.googleapis.auth.oauth2.GooglePublicKeysManager.refresh(GooglePublicKeysManager.java:172)
    at com.google.api.client.googleapis.auth.oauth2.GooglePublicKeysManager.getPublicKeys(GooglePublicKeysManager.java:140)
    at com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier.verify(GoogleIdTokenVerifier.java:174)
    at com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier.verify(GoogleIdTokenVerifier.java:192)
    at com.omarhegazi.login.GoogleAuthenticator.authenticateToken(GoogleAuthenticator.java:40)
    at com.omarhegazi.login.ServerThread.run(ServerThread.java:45)

This was using v1.6.1

I've also attempted to use v1.9.70 which results in the following:

Exception in thread "Thread-0" com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
    at com.google.apphosting.api.ApiProxy$CallNotFoundException.foreignThread(ApiProxy.java:800)
    at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:112)
    at com.google.appengine.api.urlfetch.URLFetchServiceImpl.fetch(URLFetchServiceImpl.java:40)
    at com.google.api.client.extensions.appengine.http.UrlFetchRequest.execute(UrlFetchRequest.java:74)
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:981)
    at com.google.api.client.googleapis.auth.oauth2.GooglePublicKeysManager.refresh(GooglePublicKeysManager.java:172)
    at com.google.api.client.googleapis.auth.oauth2.GooglePublicKeysManager.getPublicKeys(GooglePublicKeysManager.java:140)
    at com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier.verify(GoogleIdTokenVerifier.java:174)
    at com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier.verify(GoogleIdTokenVerifier.java:192)
    at com.omarhegazi.login.GoogleAuthenticator.authenticateToken(GoogleAuthenticator.java:40)
    at com.omarhegazi.login.ServerThread.run(ServerThread.java:45)

It looks like the fetch package gets included later than 1.6.1, but there's some issues relating to the threads in which the API calls are made.

Answer 1

As per ngueno's post above, I needed appengine-api-1.0-sdk v1.9.70 to get this working:

 <dependency>
    <groupId>com.google.appengine</groupId>
    <artifactId>appengine-api-1.0-sdk</artifactId>
    <version>1.9.70</version>
</dependency>

To resolve the "Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager" error that was being thrown with this version of the appengine API, I had to change the HttpTransport used from UrlFetchTransport.getDefaultInstance() to GoogleNetHttpTransport.newTrustedTransport()

i.e.:

    HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
    prop = new Properties();
prop.load(GoogleAuthenticator.class.getClassLoader().getResourceAsStream("config.properties"));

    GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(httpTransport, gsonFactory)
            // Specify the CLIENT_ID of the app that accesses the backend:
            .setAudience(Collections.singletonList(prop.getProperty("google.client.id")))
            .setIssuer("https://accounts.google.com")
            // Or, if multiple clients access the backend:
            //.setAudience(Arrays.asList(CLIENT_ID_1, CLIENT_ID_2, CLIENT_ID_3, etc))
            .build();

        // (Receive idTokenString by HTTPS POST)

        GoogleIdToken idToken;

        idToken = verifier.verify(inputToken);

All references and guides used had pointed to the UrlFetchTransport.getDefaultInstance() being Thread safe/the best option to use but it did not work for me here.

Answer 2

Try to include the appengine dependency in your pom.xml:

<dependency>
    <groupId>com.google.appengine</groupId>
    <artifactId>appengine-api-1.0-sdk</artifactId>
    <version>1.6.1</version> <!-- Check your version --> 
</dependency>

Link to the docs