FileService fileService = FileServiceFactory.getFileService();
    AppEngineFile file = fileService.createNewBlobFile("text/plain");
    FileWriteChannel writeChannel = fileService.openWriteChannel(file, true);

    writeChannel.write(ByteBuffer.wrap(content.getBytes()));
    writeChannel.closeFinally();
    BlobKey blobKey = fileService.getBlobKey(file);
    res.sendRedirect("/serve?blob-key=" + blobKey);
	
HTTP ERROR 500

Problem accessing /create_timetable. Reason:

The Files API is disabled. Further information: https://cloud.google.com/appengine/docs/deprecations/files_api
Caused by:

com.google.apphosting.api.ApiProxy$FeatureNotEnabledException: The Files API is disabled. Further information: https://cloud.google.com/appengine/docs/deprecations/files_api
at com.google.appengine.tools.development.ApiProxyLocalImpl$AsyncApiCall.callInternal(ApiProxyLocalImpl.java:515)
at com.google.appengine.tools.development.ApiProxyLocalImpl$AsyncApiCall.call(ApiProxyLocalImpl.java:484)
at com.google.appengine.tools.development.ApiProxyLocalImpl$AsyncApiCall.call(ApiProxyLocalImpl.java:461)
at java.util.concurrent.Executors$PrivilegedCallable$1.run(Executors.java:533)
at java.security.AccessController.doPrivileged(Native Method)
at java.util.concurrent.Executors$PrivilegedCallable.call(Executors.java:530)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)