Make TokenProvider customizable

[salbracco24]

Checklist

• I have looked into the Readme and Examples, and have not found a suitable solution or answer.
• I have looked into the API documentation and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

I want to provide custom logic to retrieve the token used to access the Auth0 Management API. Yes, I can do this by calling "setApiToken()" but that's cumbersome. I would like to implement my own token provider by implementing TokenProvider, a public interface.

Describe the ideal solution

Add a method to the builder or add a constructor for the ManagementApi class (in the com.auth0.client.mgmt package), so that TokenProvider can be changed.

You can even just make the constructor on line 35 public, but I'd prefer a new constructor, as I don't need to specify the HTTP client.

You can literally fix this issue in 10 minutes or less.

Alternatives and current workarounds

No workarounds, except reflection, which is a hack.

Additional context

Please fix this quickly, thanks.

[unkali]

Would like to add that my team is also waiting for this change. We are using reflection for the time being

[salbracco24]

Nice, I used Method Handles, which is better than reflection, @unkali:

  /**
   * Used to access a private constructor for the Auth0 {@link ManagementAPI}, so that we can use our custom
   * {@link TokenProvider}. <br> Can be removed if
   * <a href="https://github.com/auth0/auth0-java/issues/669">Auth0 Java Repo - Issue #669</a> is addressed.
   */
  private static final MethodHandle MANAGEMENT_API_CONSTRUCTOR_HANDLE;

  static {
    try {
      MethodHandles.Lookup lookup = MethodHandles.lookup();
      MethodHandles.Lookup targetLookup = MethodHandles.privateLookupIn(ManagementAPI.class, lookup);
      MethodType methodType =
        MethodType.methodType(void.class, String.class, TokenProvider.class, Auth0HttpClient.class);
      MANAGEMENT_API_CONSTRUCTOR_HANDLE = targetLookup.findConstructor(ManagementAPI.class, methodType);
    } catch (NoSuchMethodException | IllegalAccessException e) {
      throw new IllegalStateException("Failed to initialize MANAGEMENT_API_CONSTRUCTOR_HANDLE", e);
    }
  }

and then you call it like this:

try {
  return (ManagementAPI) MANAGEMENT_API_CONSTRUCTOR_HANDLE.invoke(domain, tokenProvider, DefaultHttpClient.newBuilder().build());
} catch (Throwable e) {
  throw new IllegalStateException("Failed to construct the Auth0 ManagementAPI", e);
}

But hopefully, Auth0 fixes this soon 🙏