<!-- more -->
<action-state id="moreAnswersNeeded">
	<evaluate expression="interview.moreAnswersNeeded()" />
	<transition on="yes" to="answerQuestions" />
	<transition on="no" to="finish" />
</action-state>

方法返回值类型			映射出来的EventId
java.lang.String		直接以字符串的值作为id
java.lang.Boolean		yes (for true), no (for false)
java.lang.Enum			the Enum name
any other type	    	success

<evaluate expression="pojoAction.method(flowRequestContext)" />

public class PojoAction {
	public String method(RequestContext context) {
		...
	}
}

<evaluate expression="customAction" />

public class CustomAction implements Action {
	public Event execute(RequestContext context) {
		...
	}
}

<evaluate expression="multiAction.actionMethod1" />

public class CustomMultiAction extends MultiAction {
	public Event actionMethod1(RequestContext context) {
		...
	}

	public Event actionMethod2(RequestContext context) {
		...
	}
	...
}

public class BookingAction extends MultiAction {
	public Event makeBooking(RequestContext context) {
		   try {
			   Booking booking = (Booking) context.getFlowScope().get("booking");
			   BookingConfirmation confirmation = bookingService.make(booking);
			   context.getFlowScope().put("confirmation", confirmation);
			   return success();
		   } catch (RoomNotAvailableException e) {
			   context.getMessageContext().addMessage(new MessageBuilder().error().
				   .defaultText("No room is available at this hotel").build());
			   return error();
		   }
	}
}

<decision-state id="moreAnswersNeeded">
	<if test="interview.moreAnswersNeeded()" then="answerQuestions" else="finish" />
</decision-state>

<action-state id="doTwoThings">
	<evaluate expression="service.thingOne()">
		<attribute name="name" value="thingOne" />
	</evaluate>
	<evaluate expression="service.thingTwo()">
		<attribute name="name" value="thingTwo" />
	</evaluate>
	<transition on="thingTwo.success" to="showResults" />
</action-state>

public class PrintBoardingPassAction extends AbstractAction {

    @Override
    protected Event doExecute(RequestContext context) throws Exception {
        HttpServletResponse response = (HttpServletResponse)context.getExternalContext().getNativeResponse();
        OutputStream os = response.getOutputStream();
        // 在这里操作os，写入流数据
        os.close();
        context.getExternalContext().recordResponseComplete();
        return success();
    }

}