While Activity in BPEL

While activity in bpel is just like a simple while activity in c++/JAVA .SO its general algorithm is perform certain task till the condition is valid.We will try to implement it practically in our example to understand the use case of while activity.

Our logic here is we will provide an input value which will be int and then we will call a partner link where in we will be incrementing the value of this input variable.Our while loop will check how many times we have to invoke the service.

Ok so first of all we will design a BPEL process to increment the value of input data.

First of all create an application and then create a BPEL process .Give this bpel process some logical name like Called because it will be called from another bpel process.Make this bpel process synchronous process becasue we want to pass the output value to the caller bpel process.



Now drag and drop an assign activity between the receive input and reply output.



Now double click on the assign acitivity and on the drop down box select a copy operation.

In the from choose the type as expression and provide the value

bpws:getVariableData('inputVariable','payload','/client:CalledProcessRequest/client:input')+1

It can be created from the xpath building expression window double click on the input variable in the BPEL variables table and just add 1 to it as shown below



Now assign this to the output variable so the window should appear like this






so your process is complete.Now deploy process and check that process in the BPEL console.

Just provide an input as 2 and you will get an output as 3.So we are done with one process now we will create another bpel process where in we will use our while concept.

Create one more bpel process and call it as Caller.Make this process as asynchronous process.

Drag and drop a while activity in between the input and callback as below



Expand it and drag and drop a invoke activity in it as below.



Now select services from the component pallete and drag and drop a partnerlink in the services space of the bpel designer.

a window will come up like this.



Provide the WSDL for the called process.YOu can copy it from the BPEL console.Just select the Called bpel process in dashboard and switch to wsdl you will get the wsdl file there.It will be of format

http://host:port/orabpel/default/Called/1.0/Called?wsdl

Provide it and choose the partner role as provider because the partner you are calling is the provider for the service.You role can be left untouched.

Now just automatically create the input and output variable in invoke wizard



now drag and drop a assign acctivity and put one in between receive input and while loop and other after the invoke in the while loop.
So your bpel process should now look like this



Now double click the first assign activity and create a copy operataion.

Assign the input vatiable to the input variable of the invoke activity



Double click on the second assign activity after the invoke and assign the result of the invoke activity to the input of the invoke activity.



create one more copy operation and assign the output of the invoke to the intial input variable.this we are doing as in our while loop we will be using a logic to compare with the input value that we have passed.We can creat our own varialbe and compare it it depends upon your own logic how you desing it i have chosen to assign it to the initial input variable.



Now we will specify the while condition

Click on condition expression and choose the expression builder to log in to the following wizard

there in double click the input varialbe and provide a condition that it should be less than 5 as below



now you are done with the desingning of bpel process go ahead and deploy this process.

Invoke it and provide an input as 3 so that it will be invoking the partnerlink twice.So in bpel console if you will open the flow you will get output like this





In order to clear the logic i will just write its algorithm

int i=3

while(i<5){
i++}

we are working on this simple logic.Initialized process with value 3 enter while loop and invoke the partnerlink.it will increment the value to 4,it wil check the condition it is not valid so again it will call the partner link and valur will be incremented.

We have used while activity in our java/c/c++ coding .Now just assume how much we can do the same in BPEL.Sky is not the limit, its an excuse