Hello I have an app whose backend is written in Kotlin If po

Question

Hello I have an app whose backend is written in Kotlin If possible I wouldn t like to have a different language there Is there any possibility to interact with Supertokens hosted solution Any plans to release a Java SDK Thanks

rp · Answer

hey < Iruizmar>

rp · Answer

A backend Java SDK is probably going to take a while Until then your best bet is to start another process in nodejs golang python which integrates with our backend SDKs and acts as the auth service

rp · Answer

You can directly call the core APIs from your backend but it will require you to make those APIs in your java backend which can take a while

Iruizmar · Answer

Hey < rp> thanks for that That sounds reasonable So the auth service will generate the tokens and then I can validate those on the Kotlin service to protect the routes Is there any doc on how to achieve that specially the second part

rp · Answer

There isn t specific docs for it yet but once you call the core s sign in API it will tell you if the credentials were correct or not If they are correct you can then call the core s JWT APIs to create a JWT and then send that to the frontend Verification of the JWT would be standard

Iruizmar · Answer

Ok I will try that thanks

Iruizmar · Answer

Hey mate < rp> sorry to disturb How am I supposed to return the JWT to the frontend Is it necessary to create a custom endpoint to return it I can t see any function on the frontend SDKs for that

rp · Answer

Once you call the sign in core API from your backend you need to call the JWT creation API to the core as well That will return a JWT to your backend Then the backend can send the JWT however it likes on the frontend Are you using our frontend SDK If yes which one

Iruizmar · Answer

Well the frontend is written using Kotlin Multiplatform so I thin I will just attack the API directly

rp · Answer

right In that case you should can pass the JWT to the frontend hjowever you like

rp · Answer

since it s your own API on the Kotlin side anyway

Iruizmar · Answer

Yeah So auth service using NestJs attacks core API to get a session then generates a JWT and send it back to the client All this done on a custom endpoint because there isn t any exposed automatically to do this right

rp · Answer

oh wait you re using nestjs backend

rp · Answer

We have an SDK for node js

Iruizmar · Answer

I m using nestjs just for the auth service everything else is Kotlin

rp · Answer

i see In that case the APIs for sign in etc are exposed by the nestjs service via our backend SDK

Iruizmar · Answer

I thought that was your suggestion initially haha

Iruizmar · Answer

Yes but there isn t any to retrieve the JWT is it

rp · Answer

You can enable JWTs in the session recipe > https supertokens com docs session common customizations sessions with jwt about

rp · Answer

and that will essentially add a JWT to the access token payload of the session which can be read on the frontend

rp · Answer

and then passed to the kotlin backend

Iruizmar · Answer

Is the JWT added as a cookie or how This is what I m getting using the OTP endpoint

rp · Answer

yea so it s in the front token header value See this page https supertokens com docs passwordless custom ui handling session tokens and scroll to the If not using our frontend SDK section

rp · Answer

you can essentially decode the front token and get the access token paylaod from it which will contain the JWT

Iruizmar · Answer

Awesome

Iruizmar · Answer

Thanks for that And for the super fast reply

rp · Answer

happy to help

rp · Answer

when you say kotlin frontend do you mean android frontend Or something else

rp · Answer

or is it a kotlin server just serving plain html css

Iruizmar · Answer

UI is done on native Android and native iOS and web but the domain and network logic of the three apps is shared using Kotlin Multiplatform https kotlinlang org docs multiplatform html

Iruizmar · Answer

That s why I would need a pure Kotlin SDK and I m not using Android s one

rp · Answer

ohh interesting I see

rp · Answer

Cool If you have any more questions please feel free to ask

Iruizmar · Answer

Sure mate thanks a lot