Handlers

Overview

Handlers, and in particular OutputHandlers are the means of receiving and processing the output from the Crawler. The Crawler sends its outputs, which are Matches, to its OutputHandler.

Usage

An OutputHandler requires the handle method from the Handler interface to be implemented, which is a void that simply takes an input Match and processes it (i.e uploads its contents to a database).

If one requires pre-processing before handling it, i.e converting the Match into some other object and then handling such object, they are to use a FormattingOutputHandler, which takes a MatchFormatter and a Handler that handles the generic type produced from the input MatchFormatter.

There also exists a FilteringOutputHandler, which first filters the incoming Match based upon a given MatchFilter, and then will only apply its super OutputHandler if the Match was accepted by the filter.

Examples

Below is an example of constructing an OutputHandler:

public class ExampleOutputHandler extends OutputHandler {
    public void handle(Match m) {
        // do something with the Match...
    }
}

and now constructing a FilteringOutputHandler which will first filter the Match with preset GameDurationMatchFilter and if successful pass the result to an ExampleOutputHandler (there is a Factory for FilteringOutputHandlers:

FilteringOutputHandler filteringOutputHandler = FilteringOutputHandlerFactory.get(new GameDurationMatchFilter(), new ExampleOutputHandler());

and finally constructing a FormattingOutputHandler which will first format the input Match into a Teams object which contains the team statistics as Team Orianna core objects for both teams in the Match, and then the Handler will take a Teams object and do something with the Team objects within:

Handler<Teams> teamsHandler = new Handler<Teams>() {
            @Override
            public void handle(Teams input) {
                Team red = input.getRed();
                Team blue = input.getBlue();
                // do something with the Team data...
            }
        };

FormattingOutputHandler<Teams> formattingOutputHandler = new FormattingOutputHandler<>(new TeamStatsMatchFormatter(), teamsHandler);

It's important to note that since FilteringOutputHandlers and FormattingOutputHandlers are both OutputHandlers, one may embed them within eachother to obtain filtering and formatting output handlers. If one requires this, firstly construct a FormattingOutputHandler as above, then construct a FilteringOutputHandler with its Factory, passing the FormattingOutputHandler into its get method.

Presets

One may find the following preset OutputHandlers in presets/outputhandlers. They can be extended into FormattingOutputHandlers or FilteringOutputHandlers, as above.

• PrintOutputHandler - uses a given StringMatchFormatter to format an input Match into a String, and then prints the result to System.out.
• PostFirebaseOutputHandler - uses a given FirebaseDataMatchFormatter to format an input Match into a FirebaseData object. Such FirebaseData object stores the connection to the Firebase, the path in the Firebase to post the result, and the JSON String that shall be posted at the path in the Firebase. Obtaining the context from the FirebaseData object, the handler uses the connection to post the JSON String to the Google Firebase.