Android OkHttp, refresh expired token

Question

Scenario: I am using OkHttp / Retrofit to access a web service: multiple HTTP requests are sent out at the same time. At some point the auth token expires, and

Answer 1

If you wan't your threads to bock while the first one refresh the token you can use a synchronized block.

private final static Object lock = new Object();
private static long lastRefresh;

...
synchronized(lock){ // lock all thread untill token is refreshed
   // only the first thread does the w refresh
   if(System.currentTimeMillis()-lastRefresh>600000){ 
      token = refreshToken();
      lastRefresh=System.currentTimeMillis();
   }
}

Here 600000 (10 min) is arbitrary this number should be big enouth to prevent muliple refresh call and smaller than your token expiration time so that you call the refresh when the token expires.