From Java CoG Kit

The Java class definition

Package declaration:

package my.example.element;

Import declarations:

import org.globus.cog.karajan.arguments.Arg;
import org.globus.cog.karajan.stack.VariableStack;
import org.globus.cog.karajan.util.TypeUtil;
import org.globus.cog.karajan.workflow.ExecutionException;
import org.globus.cog.karajan.workflow.nodes.SequentialWithArguments;

SequentialWithArguments (or should it be ElementWithArgumentsEvaluatedSequentially?) will automatically evaluate its arguments in sequential order.

public class MyElement extends SequentialWithArguments {

Tell it what arguments the element accepts:

    public static final Arg FIRST = new Arg.Positional("first");
    public static final Arg SECOND = new Arg.Positional("second");
    public static final Arg OPTIONAL = new Arg.Optional("optional");
    
    static {
        setArguments(MyElement.class, new Arg[] { FIRST, SECOND, OPTIONAL });
    }

Implement the functionality; post() gets called after all the arguments have been evaluated.

    public void post(VariableStack stack) throws ExecutionException {
        //add the 'first' and 'second' and multiply with 'optional' if present
        double first = TypeUtil.toDouble(FIRST.getValue(stack));
        double second = TypeUtil.toDouble(SECOND.getValue(stack));
        double result = first + second;

        if (OPTIONAL.isPresent(stack)) {
            result *= TypeUtil.toDouble(OPTIONAL.getValue(stack));                         
        }

        //return the result
        ret(stack, new Double(result));
         
        //without this the system won't know we're done         
        super.post(stack);
    }
}

The library definition

Now the mapping of the name to the implementation. Let's call the file my.xml:

<karajan>

The namespace is not required, but it may help. It's unrelated to XML namespaces.

    <namespace prefix="my">

The actual definition:

        <elementDef type="example" className="my.example.element.MyElement"/>
    </namespace>
</karajan>

Actual use

test.xml:

<karajan>
    <include file="sys.xml"/>
    <include file="my.xml"/>

    <set name="result1">
        <example first="1" second="2"/>
    </set>

    <set name="result2">
        <my:example first="1" second="2" optional="3"/>
    </set>
     
    <print message="{result1}, {result2}"/>
</karajan>

Or the other syntax. test.k:

include("sys.k")
include("my.xml")

set(result1, example(1, 2))
set(result2, my:example(1, 2, optional = 3))

print("{result1}, {result2}")