Through HTTP requests.
Setup a private web service API on your website.
A web service API is simply another interface for your web application. It's not a user interface, as users (other humans) wont be using it. It's a programming interface, meaning other software applications will use it to talk to your app.
A private web service API is simply the same as above, but with some sort of required authentication (to prevent other people using/abusing it), where only you (the dev) can use it.
Less brief explanation of an API (Application Programming Interface):
Currently, your web app has a user interface. This user interface is simply (and normally) the usage of HTML, which the users browser then renders and the user uses
it (to do whatever on your site/web app).
An API would/should not spit out HTML, as the response is not for the human eye. It should spit out JSON or maybe XML, as this is what most programming languages understand.
A really really quick and lousy example of a web service API for fetching the current date, in PHP:
//get the current date
$cDate = date( 'd-m-y' );
//we have the date, now we need to output it
//because this is a web service API, we'll output the response in JSON
//this will allow any other language (that supports (can understand) JSON) to be able to read the data from the response, appropriately.
//PHP has built-in JSON support
echo json_encode( $cDate );
If it was a user interface we were working on, we would not output JSON. Instead, we would output standard text (or HTML to make it look pretty).
So if it was a user interface, we would have
or to make it look nicer
echo '<span style="blah blah">'.$cDate.'</span>';
So once you have your web service API setup, you can come back to your Android app and start making HTTP requests. You can make POST and GET requests with Java.
For more info on HTTP requests on Android, use Google or check this out: http://stackoverflow.com/questions/...tp-post-request