Java Delegates

package my.company;

import org.activiti.engine.delegate.DelegateExecution;
import org.activiti.engine.delegate.JavaDelegate;

public class MyJavaDelegate implements JavaDelegate {

    public void execute(DelegateExecution execution) throws Exception {
        System.out.println("Hello from the class delegate");
        execution.setVariable("var1", "Hello from the class delegate");
    }

}

Build a jar with this class, and add it to the classpath. In the Service task configuration, set the class property to using the fully qualified classname (in this case my.company.MyJavaDelegate).