Finite state machine using jsf ?

I am building an online payment module and would like to implement it using a finite state machine. I am hoping that someone may give us advice on how to build it with jsf.
Firstly, I am just beginning with jsf.
Here is the example: Let's say that in the module there are 7 possible states that the user may be in, each represented by a jsp. I cannot decide where to manage state transitions. One option is to change states in the backer bean of every state, but that is dispersing transition logic across all my backer beans. The other option I can see is to have one single actionListener and have all action events pass through the 'processAction' method, keeping all the state management logic in one place.
Please comment on either of these two approaches...or any alternatives :)
Thanks in advance !
Mark

Sounds like a state machine in combination with a decorator on the ViewHandler might do the trick.
Off the top of my head I'd suggest creating a managed bean in session scope that keeps track of the state in the user's session (the state machine). Check the bean from the ViewHandler decorator when a page is requested and direct the user to the correct page if they are trying to navigate to a page that conflicts with what is allowed for their current state.
Your actionlisteners or action methods could change the user's state in the session as they process their actions.
http://forum.java.sun.com/thread.jsp?forum=427&thread=502322
The above thread discusses the use of a decorator to control navigation for authentication purposes, but it should be adaptable to this use.
Is that plausable or am I smoking crack? :-)
-jeff howard

Similar Messages

I have defined a finite state machine: pb with button : they need to be click twice

I have defined a finite state machine and also defined a call to a C dll enabling to kill processus since in my state machine I have to sequence several exe and being able to interupt them (This is the goal of mu manageProc dll)
for the moment I make my integration test with the notepad.exe process
the create and kill seems to work
but I have problem wth my finite state machine I need to click twice on the differnts button for a given state to be really effective
I have also used glabal variable and an event controller ( without that I was unable to get ffedback oo buuton click
So my question are
Is my problem due to the use of a shift register
Please tell me if you need other file to understand my problem
Regards
Thibaut
Attachments:
Spectro State MAchine .vi ‏77 KB

Thibaut,
You should put the event structure into its own parallel while loop rather than sharing the loop with the state machine. Typically the terminals of the controls will be placed inside the event case where they are read. At least inside the loop.
Run your VI with execution highlighting on (the light bulb on the diagram toolbar). This will show you how dataflow works.
You probably do not need most of your global variables. Appropriate use of shift registers and wires would eliminate them.
Lynn

Finite State Machine

hello dear coders. I'm a software engineering student and i have an assignment to create an Elevator Simulator using various programming patterns.
One of them is the an advance form of the State Pattern from Gang of Fours, the Finite State Machine.
On assignment delivery i have to justify every choice i made in implementing the patterns. I have my understanding of the FSM ( finite state machine) but i don't know if it's even near the correct form.
I'll post the classes I've made for a elevator simulator, and i would appreciate if you give me your opinion and state what i could improve and why.
I'll post also the possible state changes for the simulator requested by teacher.
States : [http://img201.imageshack.us/img201/6150/stateskz6.th.jpg]
Since they are in portuguese i'll give you the translation:
Porta Fechada = Door Closed
Porta Aberta = Door Open
Ascendente = Going up
Descendente = Going down
Parado = Stopped ( or idle )
class : StateMachine
* @author bruno
public class StateMachine {
    private AbstractState state;
    private AbstractState globalState;
    private AbstractState previousState;
    public StateMachine(AbstractState state, AbstractState globalState, AbstractState previousState) {
        this.state = state;
        this.globalState = globalState;
        this.previousState = previousState;
    public StateMachine() {
        this.state = new StateStopped();
        this.globalState = new StateGoingUp();
        this.previousState = new StateGoingUp();
    public void update() {
        if (state instanceof StateDoorClosed) {
            if (previousState instanceof StateGoingUp || previousState instanceof StateGoingDown) {
                this.changeState(this.getState().open());
            } else if (previousState instanceof StateDoorOpen || previousState instanceof StateDoorClosed) {
                this.changeState(this.getState().execute());
        } else if (state instanceof StateStopped && !(globalState instanceof StateStopped)) {
            if (globalState instanceof StateGoingUp) {
                this.changeState(this.getState().up());
            } else {
                this.changeState(this.getState().down());
        } else {
            this.changeState(this.getState().execute());
    public AbstractState getState() {
        return state;
    public AbstractState getGlobalstate() {
        return globalState;
    public void setState(AbstractState state) {
        this.state = state;
    public void setGlobalState(AbstractState globalState) {
        this.globalState = globalState;
    public AbstractState getPreviousState() {
        return previousState;
    public void setPreviousState(AbstractState previousState) {
        this.previousState = previousState;
    public void changeState(AbstractState newState) {
        this.setPreviousState(state);
        this.setState(newState);
}class : AbstractState
* @author bruno
public abstract class AbstractState {
    protected AbstractState state;
    public abstract AbstractState execute();
    public abstract AbstractState up();
    public abstract AbstractState down();
    public abstract AbstractState open();
    public abstract AbstractState close();
    public AbstractState getState() {
        return state;
    public AbstractState(AbstractState state) {
        this.state = state;
    public AbstractState() {
        this.state = this;
    public void setState(AbstractState state) {
        this.state = state;
}I omitted the concrete State Classes because of length, if you would like me to post them as-well please, don't hesitate to ask.
Sorry for the bad English and for the length of the post.
THANK YOU IN ADVANCE!

>
Two things with this code:
public void update() {
if (state instanceof StateDoorClosed) {
if (previousState instanceof StateGoingUp || previousState instanceof StateGoingDown) {
this.changeState(this.getState().open());
} else if (previousState instanceof StateDoorOpen || previousState instanceof StateDoorClosed) {
this.changeState(this.getState().execute());
} else if (state instanceof StateStopped && !(globalState instanceof StateStopped)) {
if (globalState instanceof StateGoingUp) {
this.changeState(this.getState().up());
} else {
this.changeState(this.getState().down());
} else {
this.changeState(this.getState().execute());
}Firstly, that doesn't look like a finite state machine. In a FSM the next state depends on the current state and the input it receives, whereas your machine it depends on the previous state and the global state, and no input.
Secondly, almost always if you're using instanceof to change behaviour, you're doing something wrong. It's useful for testing data you've received from a general purpose channel, such as some serialisation mechanisms or an implementation of string formatting, but it shouldn't be in the core of classes where you've designed both sides of the contract.
Usually you implement either a general purpose method to return the next state from a state given its input, or (as you have done) provide several methods to cope with the different inputs and return the next state. So the core execution logic would be for a general transition method.
get input from outside
state = state.transition(input)or for specific methods:
get input from outside
switch input
    case open: state = state.open()
    case close: state = state.close()The diagram you posted is too small to read, but it doesn't seem to have any inputs marked on the transitions, which makes the whole thing indeterminate, unless the inputs for each transition are recorded elsewhere.
Your AbstractState has a reference to another state - why ? It should either have one state for each transition out of it, or none (for example, if you make each state instance an nested class of the machine, or use an enum for the states, they don't need anything other than a transition() method, and no fields)

Need help setting up a Finite State Machine in BlueJ

Hey all, I joined these forums to hopefully help me catch up with my Java skills. I haven't programmed in Java for almost a year, and the class I'm in now does little for review so I'm rusty to say the least. The assignment we were given recently is to create a Finite State Machine resembling a gumball machine. This are basically the requirements given:
The operation of the gumball machine is simple. It takes a quarter to get a gumball dispensed. The customer needs to deposit a quarter and turn the crank, and a gumball will be dispensed if the machine contains one or more gumballs.
Design steps:
There are a number of states: No_Quarter, Has_Quarter, Gumball_Sold, Out_of_Gumballs
Create an instance variable to hold the current state and define values for each of the states.
All the actions that can happen in the system are: insert_quarter, ejects_quarter, turns_crank, dispense_gumball, and refill_gumballs. The action dispense_gumball is an internal action the machine invokes when it reaches the Gumball_Sold state.
Create a class that acts as the state machine. For each action, create a method that uses conditional statements to determine what behavior is appropriate in each state.
Write a test program to test the GumballMachine class. You consider not just normal operations i.e. insert a quarter, turn the crank; but also operations such as insert a quarter, eject the quarter, turn the crank. Or what if you turn the crank twice after insert one quarter. Or what if you insert two quarters in a row.
Now trust me, I'm not asking for someone to come here with a hunk of code and say, ok use this, and it's done. What I'm here for is hopefully someone can walk me through the right thought process of how to implement the states, and where/how to include the actions to go along with the states. We're to use BlueJ to write the code, and I'm still pretty unfamiliar with its arrow system that tells Test Programs to use the linked class(es).
Thanks for any help in advance, and for what it's worth, speedy responses are especially appreciated!

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How to do state machine using events .

Hi all.
i like to create a state machine using events methos .
i have 4 functions 1,2,3,4. (event based functios) (seperate sub vis)
1.i will trigger the 1 function.
then end of the first function should trigger the next function.
like state machine .
how to create this method in labview .. i tried value signaling its still not working . what i want.
Solved!
Go to Solution.

JGar wrote:
Wouldn't it make sense to have the entire state machine within one event case? When you trigger the event case the state machine then executes like a normal state machine.
DO NOT DO THAT!!!!!! Long parts of code do NOT belong inside of an event case.
The Event Structure should be in its own state and the state machine should to to that state every once in awhile to check for user events.
Alternatively, you could put just the state case structure inside of the Timeout event case. Something like this: http://www.notatamelion.com/2015/03/02/building-a-proper-labview-state-machine-design-pattern-pt-2/
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Finite state machines

hi
this is a bit of a stab in the dark but does anyone have experience in implementing evolving finite state machines in java. im trying to build a system of creatures who are controlled by an fsm and who compete for a limited resource. i want to control their physiology with the fsm and have them evolve more complicated competetive strategies. i just want someone to throw some ideas at and ask some questions. can anyone help?
julian.

sounds interesting. i've heard a lot about finite state machines but i've never understood what exacly is an finite state machine. we german call it "endlicher automat". is it the same as an turing machine? i have never studied computer science so i have no idea what this terms really mean.

Need help with basic user events in Queued state machine example

I have written a little queued state machine example to try to teach myself about creating and using user events. The objective of the machine is to periodically choose a number (I'm doing it now with a control instead of a random number generator for troubleshooting), and compare that number with the number I have set in a control. When they match, I want to cause an event to fire so I can do something about having found a match. The examples in the LV Help file references show the events within the event structure, but I want to reach out of a state and cause an event ....
Can someone point me in the right direction here?
Thanks
Hummer1
Solved!
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Attachments:
User Event Generator Example01 snip.png ‏102 KB

Yep....That was it...I had tried to do that but got fouled up with the variant definition...so defined the user event using a boolian and did the same in the case structure where I wanted to create the event and it worked great...
Thanks.
Here is the final version...not bulletproof, but does have a queued state machine using a user event to cause an event to fire.
Hope you find it useful.
Hummer1
Attachments:
User Event Generator Example01.vi ‏45 KB
Operating States Enum Example01.ctl ‏5 KB

Need help created state machine that is time based

I need help with my labview program. My goal is to write a program that allows the user to turn a toggle button on/off. When they do this it will start a loop witch turns on a digital switch for 45 minutes then off for 30 seconds and on and on till the user toggles the switch off. The timing does not have to be precise. I am using the NI 9476 digital output card.
I have written the code to turn the switch on/off. I know need to add the looped fuction for on 45 minutes/off 30 seconds. I assume the most efficient method would be using a state machine, but I was having trouble figuring it out.
Attached is the program I have written thus far without the loops.
Thanks,
Barrett
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Attachments:
Test Setup X01.vi ‏16 KB

I cannot see your code since I don't have 2010 installed. A state machine would be good approach but in order to allow the user to cancel and possibly abort the process at any time your state machine should have a state such as "Check for timeout". In teh loop containing the state machine use a shift register to pass the desired delay value and the start time time for that particular delay. Once the user starts the process set the delay time to your desired time (45 minutes expressed as seconds) and have another shift register that contains the next state to go to after the delay completes. Use a small delay (100ms to 500ms depending on how accurate you want your times to be) to prevent your state machine from free running and then check the delay again. Use the current time and compare it to the start time. If the desired time has passed then go to the next state. You can store the next state in a shift register. No do the same thing for your Off Time state.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot
Attachments:
Simple Delay in State Machine.vi ‏14 KB

Add an item to all state machine constants

I have a state machine using an enum for the state indicator. In
the current state, the next state is indicated by an enum
constant. If I want to add a state, how can I update all of the
constants? Here is the problem. If I add (or delete) an
item in the selector of the case structure, it is red because the enum
constants do not have that value in them. Conversely, if I add an
item to one of the constants I can "Add case for every value" and add
it to the seletor, but then I have to manually add that item to each of
the other constants. Also, the way I usually create the constants
is to pop-up on the exit tunnel for the enum in the case structure and
"Create constant". Unfortunately, that tunnel retains the choices
of the old enum and the new choice must be manually added. Is
there any way around this? I would like a method that allows me
to add or delete choices at will and have all of the constants
automatically update to match.
Roy

Well LabVIEW has just what you need in the "type def"! The next time you create a enum, right click on it, select create a control go to the front panel, right click on the control and select "Advanced" and then "Customize" to enter the control editor (if you have selected in your front panel "tools", "options", "front panel", "open the control editor with a double click", you can ust double click on the control to enter the control editor). In the control editor you will see a toolbar pull down with the "Control" option. If you pull it down and change to "Type Def" you can modify the control and all copies of it will now get automatically updated, including constants created from the type definition. The strict type def controls the look of the control as well, so it is most often used to make sure that operator interface instances of a control look the same. When you save this new type def it should ask you whether to update all instances, which will update the original control , you will have to go back and make a constant from the new control type to replace that original one, but now every copy made from that one will update when you update the type definition, and you can do that from the constant on the diagram by right clicking and selecting "open type def".
P.M.
Putnam
Certified LabVIEW Developer
Senior Test Engineer
Currently using LV 6.1-LabVIEW 2012, RT8.5
LabVIEW Champion

How can I keep a state machine readable when using large amounts of in/outputs

Hello, I am new to Labview,
Read trough the fundamentals and the
getting started and a lot of examples.
What I want to do is use a standard
state machine from the template, and add some stages, for example
orange, apple, banana. At this point I can use numeric controls to
put in the amount of oranges, apples, bananas there are. I can even
use a led to tell the user which state of the state-machine is
active.
The thing is there will be more numeric
controls and more leds and it would be nice if the code would still
be readable when there are 20 inputs and 20 outputs.
Questions
(1) It would be nice if I could use the
typedef to select the right state AND the corresponding numeric
controls and leds out of a cluster or an array kind of structure to
keep the number of wires low. Is this possible, how can I do this?
(2) I tried to put the numeric controls
into a cluster but that way I can't put the numeric control for the
apples in the upper right corner and the numeric control for the
oranges in the lower left down corner of the front panel.
(3) An example would be really nice, I
know that I saw some examples describing this problem but there are
so many examples that after a few hours of searching I haven't found
the right one yet.
Thanks in advance for the effort.
p.s. I will not use Labview to do
calculations on fruit, I am only using this to make the question
easier to understand.

I can only start a proper answer but I might as well start with that.
When I am developing State Machines I have to think about what data is used and manipulated in each state. I then have to think about where am i going to keep and manage the data. I list all of the fields that are "touched" in each state and what values are used together and which are independent form the others. After this phase of the analysis, I usually have some data structure defined (cluser array etc).
Then I flipp from thinking about the state to thinking about the data (after all this is LabVIEW and the data-flow paradigm is critical). If I see data that is only used by the State machine and is used in many of the states, then the data structure get put in a shift-register for easy access in each state. This maybe enough of an answer for your fruity question.
When i see data that is shared or only used in a handful of states then I concider putting the data in an Action Engine. Depending on how you design your AE, you can access each of the fruit totoal by name or increment etc as required.
If your app demands many fileds that are all related (can't be broken into distinct data structures) then create a cluster that has all of your values that are used by the AE. Then create an Wrapper VI for each call of the AE but only put the associated fields on the FP of the wrapper and then bundle that value into the cluster and invoke the AE.
Ben
PS: Sorry about reverting to neBulus mode but this topic could take days to cover in detail.
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

How to use a event structure with a state machine

First, I would like to inform you that I only work on LabView part time, and have much to learn. Anything I do learn, I usually forget until I need it again, because I only work on it part time.
Using your StopWhileLoopMOD[1].vi, I am trying to put a state machine inside the event structure.
Related link: http://forums.ni.com/t5/LabVIEW/How-to-stop-while-loop-in-Event-case/td-p/465564/page/2
Here is my application: on the front panel, the user can select any combination of 7 different tests. I have created cases to perform each step of each test in the correct order, but if the user presses stop, the tests won't stop because some of the cases have a while loop inside the event structure (like you mentioned is a bad idea). The user should be able to stop the test, reselect tests to perform, and re-start the tests.
When the start button is pressed for the event structure, I need all the cases to run in the proper order, unless stop is pressed.
In the past I have indexed an array and used that to run the state machine, but it won't stop immediately.
I have sub VIs that are built in while loops because the outputs of the product needs time to stabilize.  The state machine stops and waits up to a certain number of iterations. If it passes the test, the while loop stops and the next state starts. If it takes too long, it exits and reports an error. Maybe I need to just use the state machine and not an event structure?
Is there a good example of an event structure?
metzler CLAD
Solved!
Go to Solution.

I'm not sure exactly what you are asking, but it sounds like you want to script a bunch of tests and if the user says stop, to immediately stop the current test and abandon the others? I'm going to assume that you know how to clear the array so that it will abandon the others, so I'm guessing that you are having trouble abandoning the current test? If this is indeed the case, then the problem is that you are not able to propagate the message from the main VI FP which is the GUI to the sub vi which is the test, where the test may or may not have a GUI (FP visible) of it's own. Threading was the first thing to come to mind, but this may not be necessary using events.
You can do this by passing a refnum of the stop button to the subVI, where you can then add that wait to the event case structure.
I've attached 2 VIs, mainvi.vi which is just a loop displays the count*2 (number of seconds passed since running) that will call subvi.vi and then check to see if the stop button is pressed. mainvi.vi is by no means a state engine, it is just a simple loop for demonstration purposes. subvi.vi just waits 2 seconds and leaves, it is a better structured state engine with an init state to start a poll case to wait for events and an exit state to clean up. You can modify this any way you wish to get it to do what you want. You will note that even if subvi.vi is being executed, it will terminate immediately when the stop button is pressed.
Hope this helps.
A
Attachments:
mainvi.vi ‏17 KB
subvi.vi ‏33 KB

How to use elapsed time function with state machine in Lab VIEW

Hello
I've been trying to use state machine with elapsed time function in order to sequentially start and stop my code. The arrangement is to start the code for 1 minute then stop for 5 minutes. I've attached the code, the problem is when I place the elapsed time function out of the while loop it doesn't work, on the other hand when I place it inside the loop it does work but it doesn't give the true signal to move to the next state.
Could you please have a look to my code and help me to solve this issue.
Regards
Rajab
Solved!
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Attachments:
daq assistance thermocouple(sate machine raj).vi ‏436 KB

Rajab84 wrote:
Thanks apok for your help
even with pressing start it keeps running on wait case
could you please explain the code for me, the use of Boolean crossing, increment , and equal functions
Best Regards
Rajab
OK..I modded the example to stop after 2 cycles. Also recommend taking the free online LabVIEW tutorials.
run vi. case statement goes to "initialize", shift registers are initialized to their constants. goto "wait"
"start"= false, stay in current state. If true, transition to "1 min" case
reset elapsed timer with True from shift register(counter starts at zero)."time has elapsed"=false, stay in current state(1 min). If true, goto "5min" case
reset elapsed timer with True from shift register of previous case(counter starts at zero)."time has elapsed"=false, stay in current state(5 min). If true, goto "1min" case. Also, bool crossing is looking for "true-false" from "5 min" compare function to add cycle count.
Once cycle count reaches 2, stop while loop....
Attachments:
Untitled%202[1].vi ‏42 KB

Advantages of Using Queued Message Handler vs. Standard State Machine

Hello,
What are the advantages of using a Queued Message Handler? Also, why are they more powerful than using Standard State Machines?
Thanks!

They are really just sort of an extension of a state machine. The general idea is that you have one loop doing a specific job. You then use a queue to tell it how/when to do this job. For instance, I might have a log file loop. I will send it commands to open a file, write some data, write some more data, and finally close the file. Each of those commands are coming from the queue. The beauty with this setup is that anybody that can get a reference to that queue can send the command to that loop.
So the QMH is "better" than a state machine mostly because of the decoupling of functions. In a given application, I will have a loop for log file writing, GUI updates, reading of a DAQ, instrumenet communications, server communications, etc. Trying to do all of that in a single loop state machine is a major pain in the rear end. Seperating them out makes life so much easier.
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Create Multiple tasks for Single Item in List using state machine workflow in sharepoint

Hi,
I want to create multiple create tasks for Single Item in List based on Assigned to column using state machine Workflow through visual studio
Here Assigned to column allows multiple users. so i have to create task for every user based on column .
I'm trying for this but i didn't got any solution
Please provide solution for this.

Hi,
According to your post, my understanding is that you wanted to allow multiple users to approve.
There are some articles about creating parallel tasks in state machine workflow, you can have a look at them.
http://www.codeproject.com/Articles/477849/Create-Parallel-Task-in-State-Machine-Workflow-in
http://msdn.microsoft.com/en-us/library/office/hh128697(v=office.14).aspx
http://social.technet.microsoft.com/Forums/office/en-US/b16ee858-4360-479a-a686-4ee35b7be9db/sharepoint-2010-workflow-creating-multiple-tasks?forum=sharepointdevelopmentprevious
Thanks & Regards,
Jason
Jason Guo
TechNet Community Support

State machine with using event case

Hallo everyone,
i have a question about how to realize the "Timeout". In the flow diagram below we can see 2 different situation:
1. in the 1st Situation i have used the state machine, it begins at state 1, which contains a event case. In there it will be at first determined, if the input value has changed within 10 second, if it didn't, the state machine will go to state 2, if it 's changed, will be furthermore determined, whether the input value equal to 3, if yes, the state mashine will jump to state 3, if no, jump back to state 1. (this VI i have done before, you can take a look at the Attachment).
2. my question is in the 2nd situation. It begins also at state 1. In there the input value can also be changed (once or many times) or not. If the value has not been changed within 10 s, or even though it's been changed many times within 10s, but it's never been equal to 3, the state machine will go to state 2; only when the input value within 10s equal to 3, it can jump to state 3.
This problem i have no idea how to solve, does anybody have idea or better methods?
thanks a lot!!
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Attachments:
situation 1.vi ‏12 KB

The statement in the OP is not covering all cases.
mexaviesta wrote:
2. my question is in the 2nd situation. It begins also at state 1. In there the input value can also be changed (once or many times) or not. If the value has not been changed within 10 s, or even though it's been changed many times within 10s, but it's never been equal to 3, the state machine will go to state 2; only when the input value within 10s equal to 3, it can jump to state 3.
This problem i have no idea how to solve, does anybody have idea or better methods?
thanks a lot!!
Just check my implementation for Situation 2 and let us know, if it works for you.
I am not allergic to Kudos, in fact I love Kudos.
Make your LabVIEW experience more CONVENIENT.
Attachments:
Situation 2.llb ‏40 KB

Finite state machine using jsf ?

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