Fusion

Asynchronous BPEL Process

A Asynchronous Process is one which you call and need not wait for the response before proceeding further. You may just initiate the Asynchronous process and receive the response when you require it as a part of your process, hence you are not forced to wait for response.

For analogy sake, let me give you an example for better understanding. I have chosen simplicity of the analogy above technical similarity.

Real life example of a Synchronous process: You call a friend and ask him to give you some information. While your friend is finding out the information for you, you are on the call waiting for his response. Note that connection is not dropped

Real life example of an Asynchronous process: You call a friend and ask him to give you some information. You ask him to call you back when the information is ready and you disconnect the call. When your friend is ready with the information, he calls you and gives you the information. Note that you don’t wait for a response from your friend and connection is lost. When your friend is ready, he has to establish a new connection and then provide you the information

Anil has done an excellent job in making us create a HelloWorld. We will modify it to suit our needs for an asynchronous process.

This tutorial will be in 3 steps:

1)       First we will create a Asynchronous HelloWorld, a variant of the basic Hello World process created by Anil.

2)       We will call the asynchronous Hello World, asynchronously from another BPEL process we create.

3)       (Optional) We will modify our Asynchronous process to understand asynchronous process better

Note that if you have created a synchronous Hello World Process like Anil has suggested, it will not work in the steps I have followed.

We will run through the process and I will do a post-mortem / autopsy at important places to explain what we accomplished.

Create a BPEL Process Name : HelloWorldAsync

Right click on Application è New Project è Integration Tier : BPEL è BPEL Process Project

Name = HelloWorldAsync

Namespace = <Default>

Template = Asynchronous BPEL Process

Lets keep the defau values for Input Schema Element and Output Schema Element.

Choose Finish.

Our BPEL Process will look something like this :

Choose Assign activity from the Component Palette and drag and drop between receiveInput  and callbackClient

Double click on Assign activity to rename it to AssignHello.

Go to Copy Operation tab and click on Create è Copy Operation

From :

Type = Expression è Expression : concat('Hello ', bpws:getVariableData('inputVariable','payload','/client:HelloWorldAsyncProcessRequest/client:input'))

Note that, you can press Ctrl+Space Bar to help you in forming the expression above

To :

Type = Variable è Variables è Process è outputVariable è payload è client:HelloWorldAsyncProcessResponse è client:result

Choose OK

Choose OK

Our HelloWorldAsync BPEL Process will like this :

Let us understand what we have accomplished.

We first created an Asynchronous BPEL Process which already has 2 nodes created :

1)       receiveInput ( This receives the input)

2)       callbackClient (This generates output and sends response asynchronously)

If you double click on receiveInput or callbackClient, you will see each of them has only one variable.

receiveInput è inputVariable

callbackClient è outputVariable

If you have created a Synchronous BPEL Process, you will realize that in a synchronous process we have 2 nodes, receiveInput and replyOutput, while in Asynchronous BPEL Process replyOutput is replaced by callbackClient.

Lets recollect the analogy I mentioned in the beginning of the article.

Real life example of a Synchronous process: You call a friend and ask him to give you some information. While your friend is finding out the information for you, you are on the call waiting for his response. Note that connection is not dropped

Real life example of an Asynchronous process: You call a friend and ask him to give you some information. You ask him to call you back when the information is ready and you disconnect the call. When your friend is ready with the information, he calls you and gives you the information. Note that you don’t wait for a response from your friend and connection is lost. When your friend is ready, he has to establish a new connection and then provide you the information

As you can infer from above analogy, the node callback client has to re-initiate the connection with the parent process and then respond with the output, unlike replyOutput where the connection is all there to receive the response.

To illustrate the asynchronicity lets add a Wait activity which will wait for 30 seconds before giving us a result

Drag and drop a wait activity between AssignHello and callbackClient.

Double click on Wait activity to change the name and set the wait time to 30 seconds.

Make sure all others time attributes are zero.

Right click on HelloWorldAsync è Make

Right click on HelloWorldAsync èDeploy è <IS Name> è Deploy to default domain

In Apache Ant you would see BUILD SUCCESSFUL

Before we use it, lets test it.

When the BPEL Process is deployed, we will have to test it. Go to IS Server where our BPEL Process is deployed. BPEL Process Manager è BPEL Control è Username/password è Dashboard

You will see HelloWorldAsync è click on it

Type your input (in this case Sudeept) and choose Post XML Message

Click on Visual Flow

Click on Refresh View on the top right to go past the wait process.

When the wait activity is complete, the process will complete with output Hello Sudeept

Now we will do the step 2 of the tutorial.

We will create a BPEL Process which will call HelloWorldAsync asynchronously

Create a BPEL Process Name : AsynchronousBPELProcess

Right click on Application è New Project è Integration Tier : BPEL è BPEL Process Project

Name = AsynchronousBPELProcess

Namespace = <Default>

Template = Asynchronous BPEL Process 

Choose Next

Let us use the default names for Input Schema Element and Output Schema Element

As explained in HelloWorldAsync note the callbackClient node and how it is different from replyOutput.

 Now we will create a place holder for HelloWorldAsync on our AsynchronousBPELProcess 

In Component Palette è Services è Partner Link

Drag and drop the Partner Link on the right side grey area called Services

Double click on PartnerLink to edit it

Name = HelloWorldAsync

To link this place holder to the HelloWorld Process, click on the torch icon above WSDL File:

Make sure you are connected to your IS Server.

We will connect to the IS Server and select the already deployed HelloWorld Process

BPEL Services è <IS Server Name> è processes è default è HelloWorldAsync

Choose OK.

Partner Link Type = HelloWorldAsync

PartnerRole = HelloWorldAsyncProvider

My Role = HelloWorldAsyncRequester

Note that HelloWorldAsyncRequester will now show up in the drop down for My Role unless HelloWorldAsync is a asynchronous process. This is the reason, we created a new asynchronous Hello World process and couldn’t use the Hello World created by Anil earlier.

Also note that, while creating the synchronous process in my earlier tutorial, I had pointed out that My Role is blank while calling a synchronous process, while it is not a blank while calling a asynchronous process.

Now we will call ( invoke ) the HelloWorldAsync BPEL Process asynchronously

In Component Palette è Process Activities è Invoke

Drag and drop Invoke activity between receiveInput and callbackClient.

Double click on Invoke activity to edit it.

Name = InvokeHelloWorldAsync

Click on the torch icon next to Partner Link

Partner Links è Process è Partner Links è HelloWorldAsync

Click on Automatically create input variable icon next to Input Variable

Use the default value and choose OK

Note that Output Variable is disabled as we are calling an asynchronous process. If you have completed the tutorial on Synchronous BPEL process, you will realize that it was enabled while calling a synchronous process.

Our process AsynchronousBPELProcess looks like this:

Unlike calling a synchronous process, calling a asynchronous process involves 2 activites, invoke and receive.

Let us add a Receive activity to our BPEL Process.

In Component Palette è Process Activities è Receive

Drag and drop Invoke activity between InvokeHelloWorldAsync and callbackClient.

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