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The protocol handler receives data from a transport handler and prepares it for the data handler or receives data from the data handler and prepares it for the transport handler. A simple protocol is a comma separated list (CSV).

To create a new protocol handler AbstractProtocolHandler must be extended (or IProtocolHandler implemented). Two constructors are needed. A default constructor for OSGi and a constructor with the arguments in the codeblock below. The super constructor needs to be called with these arguements, they are needed for the connection of the transport-, protocol- and data-handler.

public YourProtocolHandler() {
		super();
} 
 
public YourProtocolHandler(ITransportDirection direction, IAccessPattern access, OptionMap options,
			IStreamObjectDataHandler<T> dataHandler) {
		super(direction, access, dataHandler, options);
}   
 
/**
 * Creates a new protocol handler
 * @param direction is this handler used in a source (IN) or in a sink (OUT)
 * @param access which kind of access pattern is supported (  PUSH,  PULL,  ROBUST_PUSH,  ROBUST_PULL)
 * @param options set of options as key value pairs
 * @param dataHandler the data handler thats connected to the protocol handler
 * @return
*/
public IProtocolHandler<T> createInstance(ITransportDirection direction, IAccessPattern access,
            Map<String, String> options, IDataHandler<T> dataHandler) {
		return new YourProtocolHandler<>(direction, access, options, dataHandler);
}

The following method could be overwritten:

open(): This method is called, when the query is started.
Important: When overwriting this method, getTransportHandler().open() must be called, too.
close(): This method is called, when der query is stopped.
Important: When overwriting this method, getTransportHandler().close() must be called, too.

Pullbased

boolean hasNext(): must be overwritten, to state if a new element is available for processing
T getNext(): must be overwritten to deliver the next element
boolean isDone(): can be overwritten to state if a source will not deliver anymore elements

Pushbased

For pushbased access the methods from the Interface ITransportHandlerListener need to be overwritten:

    /**
     * Is called when a new connection with the transport handler is established
     * @param caller
     */
    void onConnect(ITransportHandler caller);
    
    /**
     * Is called when an existing connection to the transport handler is interrupted
     * @param caller
     */
    void onDisonnect(ITransportHandler caller);
    
    /**
     * Implement this method to process the message
     * @param message as ByteBuffer
     */
    void process(ByteBuffer message);
    
    /**
     * Implement this method to process the message
     * @param message as String Array
     */
    void process(String[] message);
    /**
     * Implement this method to process the message
     * @param message as T
     */
    void process(T m);

Typically, these methods are called from the underlying transport handler