Tip: Accessing a flow execution from outside Spring Web Flow

[fanfy]

Seems that this works. I post it here maybe someone else will need it.

import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
import org.springframework.validation.Errors;
import org.springframework.webflow.action.FormObjectAccessor;
import org.springframework.webflow.context.ExternalContext;
import org.springframework.webflow.context.ExternalContextHolder;
import org.springframework.webflow.context.servlet.ServletExternalContext;
import org.springframework.webflow.execution.FlowExecution;
import org.springframework.webflow.execution.repository.FlowExecutionKey;
import org.springframework.webflow.execution.repository.FlowExecutionRepository;
import org.springframework.webflow.executor.FlowExecutorImpl;
import org.springframework.webflow.executor.mvc.FlowController;
import org.springframework.webflow.executor.support.FlowExecutorArgumentHandler;
import org.springmodules.xt.ajax.FormDataAccessor;

/**
 * 
 * @author Elvis Ciocoiu
 *
 */
public class SWFFormDataAccessor implements FormDataAccessor {
	private static final Logger LOG = Logger.getLogger(SWFFormDataAccessor.class);
	
	public Object getCommandObject(HttpServletRequest request,
			HttpServletResponse response, Object handler, Map model) {
		
		Object command = extract(request, response, (FlowController) handler, new SWFAccessorCallback() {

			public Object extract(FlowExecution flowExecution) {
				return flowExecution.getActiveSession().getScope().get(FormObjectAccessor.getCurrentFormObjectName());
			}
			
		});
		
		return command;
	}

	public Errors getValidationErrors(HttpServletRequest request,
			HttpServletResponse response, Object handler, Map model) {
		Errors errors = (Errors) extract(request, response, (FlowController) handler, new SWFAccessorCallback() {

			public Object extract(FlowExecution flowExecution) {
				return (Errors) flowExecution.getActiveSession().getFlashMap().get(
						FormObjectAccessor.getCurrentFormErrorsName(), Errors.class);
			}
			
		});
		
		return errors;
	}

	private Object extract(HttpServletRequest request,
			HttpServletResponse response, FlowController flowControllerflowControllertroller, SWFAccessorCallback callbak) {
		FlowExecutionRepository repository = ((FlowExecutorImpl)flowControllerflowControllertroller.getFlowExecutor()).getExecutionRepository();
		FlowExecutorArgumentHandler argumentHandler  = flowControllerflowControllertroller.getArgumentHandler();
		
		ExternalContext externalContext = new ServletExternalContext(request.getSession().getServletContext(), request, response);		
		
		if (argumentHandler.isFlowExecutionKeyPresent(externalContext)) {
			try {
				ExternalContextHolder.setExternalContext(externalContext);
				FlowExecutionKey flowExecutionKey =
					repository.parseFlowExecutionKey(argumentHandler.extractFlowExecutionKey(externalContext));
				FlowExecution flowExecution = repository.getFlowExecution(flowExecutionKey);
				
				return callbak.extract(flowExecution);
			}
			catch (Exception e) {
				e.printStackTrace();
			}
			finally {
				ExternalContextHolder.setExternalContext(null);
			}
		}
		
		return null;
	}

	interface SWFAccessorCallback {
		Object extract(FlowExecution flowExecution);
	}
}

[Saloucious]

Hi, i'm working with SWF on Liferay portal.

Each portlet has his own PortletFlowController instance and, AFAIK, his own WebApplicationContext.

I would like to create a Servlet in my web app to be able to stream PDF file.

But actually i'm not able to access to a flow execution contained by one of my portlets.

Any ideas ?

Thans

[dvermeir]

Is there a webflow 2 version for this tip ?

We are using this for a Spring MVC controller that returns "image/jpeg" content. The bytes of the image are stored on flowscope and so we need to access the flowscope from within our MVC controller.
In webflow 1 this worked out just fine and we tried these changes to get it working in webflow 2.0.8:

ApplicationContext context = (ApplicationContext)getServletContext().getAttribute(DispatcherServlet.SERVLET_CONTEXT_PREFIX + "x");

FlowController controller = (FlowController)context.getBean("flowController");
FlowExecutionRepository repository = ((FlowExecutorImpl)controller.getFlowExecutor()).getExecutionRepository();

ExternalContext externalContext = new ServletExternalContext(getServletContext(), request, response);
ExternalContextHolder.setExternalContext(externalContext);
FlowExecutionKey flowExecutionKey = repository.parseFlowExecutionKey(ServletRequestUtils.getRequiredStringParameter(request, "_flowExecutionKey"));

FlowExecution flowExecution = repository.getFlowExecution(flowExecutionKey);

MutableAttributeMap flowScope = flowExecution.getActiveSession().getScope();

However, this does not seem work 100%. Sometimes we get "SnapshotNotFoundException" for some of our images. It isn't really clear and there is no rule as to when this exception occurs.

[buntyindia]

please update this tip as per latest webflow api

[aruncollections]

Is there any update on this ?