Obtaining the Config and Connection in a Message Source

Obtaining the Config Object

Just like operations, a source might reference a configuration to obtain parameters about its behavior. To obtain such a configuration, a field must be annotated with the @Config annotation (the same used in operation arguments):

public class HttpListener extends Source<InputStream, HttpRequestAttributes> {

  @Config
  private HttpListenerConfig config;
}

Obtaining a Connection

If the source requires a connection (and 99% of connectors do unless you are implementing a Scheduler), you need to obtain a connection. As with operations, the @Connection annotation is used but with two major differences:

It is used in a field instead of a method argument.
Instead of the connection object, a ConnectionProvider is injected.

public class HttpListener extends Source<InputStream, HttpRequestAttributes> {

    @Config
    private HttpListenerConfig config;

    @Connection
    private ConnectionProvider<HttpServer> serverProvider;

    @Parameter
    @Optional(defaultValue = "/")
    private String path;

    private HttpServer httpServer;

    @Override
    public void onStart(SourceCallback<InputStream, HttpRequestAttributes> sourceCallback) throws MuleException {
        httpServer = serverProvider.connect(); (1)

        httpServer.listen(path).onRequest(request -> { (2)
            processRequest(request, sourceCallback); (3)
        });
    }

    @Override
    public void onStop() {
        if (httpServer != null) { (4)
            serverProvider.disconnect(httpServer); (5)
        }
    }
}

1	The example uses the `ConnectionProvider` to obtain an `HttpServer`. The typical connection provider has already configured the server with the proper host and port.
2	HTTP requests are pushed into the server by the remote clients, and the `HttpServer` component notifies the source of every request. The source then uses the `SourceCallback` to push the message into the flow.
3	The source should define the `processRequest` method to transform the HTTP request into a message that can be pushed to the flow. The documentation will show how to do that later, but to keep the example simple, you can assume that this works.
4	The `onStop()` method releases resources, in this case, the `HttpServer`. It checks for null in case the `onStart()` method fails before the server is created.
5	The example uses the `disconnect()` method of the `ConnectionProvider` to release the server.

The example above is pseudocode. It oversimplifies the real HTTP connector to keep the example clear and concise.

Next Step

Pushing Messages to a Flow from a Message Source