I don't know if it is only me, but I really see great potential for applying SWF on business logic field… Let me explain this a little. Recently I have done some work with commons chain. Isolation of business logic in small independent and focused parts call for creation of some kind business logic library which can be later combined easily (and declaratively) via chains. That seemed as a great idea at first but than I bumped at some obstacles down the road. I.e. very often there is a need for translation of parameters between commands (since they supposed to be totally in dependable of each other) and some branching mechanism (simple if) is also missing. I understand that commons chain is implementation of "Chain of responsibility" pattern, but still I will like those features.
One can also argue that I can simply use one of popular full featured open source business workflow engines such as OSWorkflow or JBoss jBPM. But they are almost always focused on complicated workflows with discontinuations and they always require some database. I don't really need this. I just want some simple workflow which can support one-pass execution of business logic commands with some nice add on features like branching and attribute mapping. Nothing more (and nothing less).
Then SWF comes along. It contains all mentioned features missing from commons chain, but it is focused primarily on web flow (al least that impression can be gained from available documentation). Nevertheless I was still done some investigation to see if SWF can be used as a simple workflow engine (maybe "micro workflow" term will be more appropriate) and fortunately it can :) Here is how:
Workflow and action definition:
<webflow id="sampleflow" start-state="sampleState">
<action-state id="sampleState">
<action bean="sampleActions"/>
<transition on="success" to="successState"/>
</action-state>
<end-state id="successState" view="dummy"/>
</webflow>
public class SampleAction implements Action {
public Event execute(final RequestContext p_context) {
System.out.println(p_context.getSourceEvent().getA ttribute("param1"));
p_context.getFlowScope().setAttribute("myparam", "myparam - flow output");
return new Event(this, "success");
}
}
Tester and applicationConfig definition:
public class Tester {
public static void main(final String[] p_args) {
ApplicationContext context = new ClassPathXmlApplicationContext("swfexperiments/applicationConfig.xml");
Flow flow = (Flow)context.getBean("sampleFlow");
FlowExecution flowExecution = new FlowExecutionImpl(flow);
Map eventParams = new HashMap();
eventParams.put("param1", "param1 - flow input");
Event startEvent = new Event(new Object(), "startEvent", eventParams);
Map model = flowExecution.start(startEvent).getModel();
System.out.println(model.get("myparam"));
}
}
<beans>
<bean id="sampleFlow" class="org.springframework.web.flow.config.XmlFlowFactory Bean">
<property name="location" value="classpath:swfexperiments/sampleFlow.xml"/>
</bean>
<bean id="sampleActions" class="swfexperiments.SampleAction" />
</beans>
And that’s it. Thank you SWF guys :)