State Machine Complier And Asp.net

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Introduction

The workflow activity has become a core business process in various domains. There are many technologies that provide the solution to design workflow activity and a mechanism to process the work request as per the user role or state of activities. One of them is Windows Workflow foundation. WWF provides a solution to such problem, but with very complex architecture to achieve this .This involves significant amount of production time. The workflow activity is not static it varies with change in business process. To deal with this problem we have state machine complier which provides out of the box solution to it. SMC is an open source code. This article demonstrate and help one to understand the implementation workflow using State Machine Compiler in .Net.

Reference: State Machine Compiler

System Requirement

Syntax: State Machine definition

Here is the syntax to start writing state machine workflow definition.Below diagram is self explanatory.

[State]
{
[Transition Method]  	[Transition State]
{
	[Action Method]
}
}

Semantics: State Machine definition

The semantics below describes the use of gaurd condition,multiple transition and actions performed on state changed. These semantics thus solves lot of business problem statement.Below is the list of semantics required to write sm file.

1) If there is no action for a given transition.

StateName 
	{
	    TransitionMethodName() TransitionStateName 
    	    {}
	}

2) One can pass input arguments to transition method.

StateName 
	{
    		TransitionMethodName (userId: String) TransitionStateName 
		{}
    	}

3) One can have Guard Condition for multiple Transitions within a state definition.

StateName 
	{
    		TransitionMethodNameFalse()[!contextBusinessObj.IsState]         
                 TransitionStateName1
                 Action1	{}

		TransitionMethodNameTrue()[contextBusinessObj.IsState]         
                 TransitionStateName2
                 Action2	{}

    	}

4) If there is no action for a given transition.

StateName 
	{
    		TransitionMethodName ()         
               Nil
          	{}

    	}

Problem Statement

Here we have to create state machine workflow for CAR-Vehicle. As car can have four state Start ,Run,SlowDown and Stop.Taking these state I have designed a small demo project which demonstrate how to use SMC in .net. The prior knowledge of workflow can help one to understand this demo quickly.Lets us follow the below step to create workflow for this problem statement.

Steps To Integrate SMC With .Net

Below diagram depicts the picture how state change occured in workflow.This diagram is state activity diagram which help us to understand the state transition from start to end.

State Machine Flow Diagram

1. Create State machine defination file called .SM file, for CAR workflow.

Taking above semantics and syntax we can create sm file. Below is the sm created for CAR automation workflow.Here the CarEntity is the object of business entity Car. The action UpdateState has takes three argument one car object,Next state and Current state.So in UpdateState we specify the next possible state for given current state.

Car State Machine Definition

%class CarWF %package StateMachineWorkflowActivity %import StateMachineWorkflowActivity %start MainMap::Start %map MainMap %% Start { SubmitRun Run { UpdateState(ctxt.CarEntity , Utilities.CarState.Run, Utilities.CarState.Start); } SubmitStop Stop { UpdateState(ctxt.CarEntity , Utilities.CarState.Stop , Utilities.CarState.Start); } } Run { SubmitSlowDown SlowDown { UpdateState(ctxt.CarEntity , Utilities.CarState.SlowDown, Utilities.CarState.Run); } SubmitStop Stop { UpdateState(ctxt.CarEntity , Utilities.CarState.Stop , Utilities.CarState.Run); } } SlowDown { SubmitStop Stop { UpdateState(ctxt.CarEntity , Utilities.CarState.Stop , Utilities.CarState.SlowDown); } } Stop { } %%

2. Run the Command To Generate the CSharp Class From SM File

Run the below command in command prompt to generate workflow CSharp file.

java -jar "D:\SMC_Demo\Smc.jar" -reflect -serial -csharp  "D:\SMC_Demo\CarWF.sm"

3. Create Persistence mechanism In Database

In workflow it is very important to implement persistence mechanism where we can store the context of each entity and activity in database.Here I design very simple workflow saving mechanism.Create database named CarAutomation. There will be three table in it. The significance is stated as follows:

Database Diagram

4. Create Solution in .Net

Refer source code for more information.

Here is the class diagram for stateMachineWorkFlowActivity package.

Create Car Dashboard.

In UI mode user view workflow dashboard.This dashboard is the workflow activity screen where one initiates state transition and perform appropiate actions as defined in state definition file. User clicks on respective CAR ID and perform state transition for it. The URL for each state transition is maintain in database table.

Once the user clicks on CAR ID ,he/she is redirected to state activity page for the current state. Here user can clicks on 'Run','Slowdown' or 'Stop'. If user clicks on Run and Stop ,the action is perform as it is correct rules as per .SM file definition.

protected void btnRun_Click(object sender, EventArgs e)
    {
        try
        {
            Car car = new Car();
            car.CarID = Convert.ToInt32(ViewState["CAR_ID"]);
            car.Remark = "State Machine Compiler:Run Car";
            car.State = (Utilities.CarState)Convert.ToInt32(ViewState["State"]);
            car.User = 444;


            StateMachineWorkflowActivity.IWFFactory m_WFactory = new StateMachineWorkflowActivity.WFFactory();
            StateMachineWorkflowActivity.ICarWF m_CarWF = m_WFactory.StartWorkFlowStateMachine(car);

            m_CarWF.SubmitRun();
            Response.Redirect("CarDashboard.aspx", false);
        }
       catch (Exception ex)
        {
            if (((statemap.TransitionUndefinedException)(ex)) == ex)
            { 
            ClientScript.RegisterClientScriptBlock(GetType(),"Key1","alert('This is undefined Workflow State.')");
            }
        }
    }

If user clicks on Slowdown for current state 'Start', it will prompt for undefined state transition.

Conclusion

Hope this article will help the developer who needs reference for State Machine Compiler. This is just initiative towards presenting one working model of SMC integration with ASP.net.

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)