google app engine - How to access file present inside bucket of another application -

i trying read .txt file present inside bucket of google application.

below code

              gcsinputchannel readchannel = null;               bufferedreader reader = null;               gcsfilename filename = new gcsfilename("abc.appspot.com","for_prod_scripts.txt");                gcsservice gcsservice = gcsservicefactory.creategcsservice();               // can read file through api:               readchannel = gcsservice.openreadchannel(filename,0);               // again, different standard java ways of reading channel.               reader = new bufferedreader(channels.newreader(readchannel, "utf8"));               //csvreader csvreader = new csvreader(reader);               string line = reader.readline();                while ((line = reader.readline()) != null) {                   log.warning("read:" + line);                 } 

i have added below permissions bucket permissions , object default permissions of bucket.as shown in below image. 123412341234 application's project id. inside accessing bucket

i getting below exception

java.lang.runtimeexception: com.google.appengine.tools.cloudstorage.simplegcsinputchannelimpl$1@1f75e55: unexpected cause of executionexception 

am missing here?

need add service account email bucket permissions accessing files inside buckets.