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Dynamically Adding Ports with the PortPairExtender

Sometimes it's useful to add ports that simply pass data through the operator without changing it - 'through' ports. If your operator does not need input and output ports, best practice is to add through ports to control the process execution order. The PortPairExtender, a sub-class of PortExtender, ensures that the through ports are pair-wise.

../img/operator-with-through-ports.png

The PortPairExtender is also used to pass input data from a super operator to its subprocesses. You can find more details in the advanced chapter about super operators.

Adding through ports

To define through ports, simply add a PortPairExtender as a private variable, using the following code:

private final PortPairExtender dummyPorts = 
    new DummyPortPairExtender("through", getInputPorts(), getOutputPorts());

Then, initialize the ports and add the pass through rule to handle the meta data:

dummyPorts.start();
getTransformer().addRule(dummyPorts.makePassThroughRule());

Add the command to pass the data from the input through ports to the output through ports at the end of the doWork() method.

dummyPorts.passDataThrough();

Simple example operator with through ports

public class MyOwnOperator extends Operator {

    private PortPairExtender dummyPorts = 
        new DummyPortPairExtender("through", getInputPorts(), getOutputPorts());

    public MyOwnOperator(OperatorDescription description) {
        super(description); 

        dummyPorts.start();
        getTransformer().addRule(dummyPorts.makePassThroughRule());
    }

    @Override
    public void doWork() throws OperatorException {
        LogService.getRoot().log(Level.INFO, "Doing something...");

        // PASS THROUGH PORTS
        dummyPorts.passDataThrough();
    }
}

The next step is to add parameters to your operators.

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Dynamically Adding Ports with the PortPairExtender

Adding through ports

Simple example operator with through ports