Mapping Favicon.ico In A Golang Application

One of the most annoying issues about configuring a Go based app is correctly mapping every file to its proper path.

For instance, beginners at Go frequently declare their first handler like so:

http.HandleFunc("/", handler)

And declare a simple app.yaml, similar to the one below:

application: application_id
version: 1
runtime: go
api_version: go1

handlers:
- url: /.*
  script: _go_app

Unfortunately this will cause all requests to be routed to your Go application code, even if you have static files in your application’s root directory.

To map favicon.ico (or any static file in the app’s root directory) so AppEngine will serve it, replace the handlers section in app.yaml to properly indicate where it is and the url it maps to:

handlers:
- url: /favicon\.ico
  static_files: favicon.ico
  upload: favicon\.ico
- url: /.*
  script: _go_app

Sending Mail With The Java Low Level API

Code example on how to send mail using the Java low level API. This code generates the appropriate From address based on your application’s ID.

MailService.Message message = new MailService.Message();
message.setSubject(subject);
message.setTextBody(body);
String application_id = SystemProperty.applicationId.get();
String sender = "[email protected]" + application_id + ".appspotmail.com";
message.setSender(sender);
MailServiceFactory.getMailService().sendToAdmins(message);

Retrieving A Datastore Entity With A Key (or Kind Name & ID)

Short code fragment that someone might find useful: retrieve an Entity if you know what the kind and entity ID/name are.

Key key = KeyFactory.createKey("kind", "id/name");
try {
    Entity entity = DatastoreServiceFactory.getDatastoreService().get(key);
} catch (EntityNotFoundException e) {
    //The entity wasn't found. Handle this exception.
}