Launch JDeveloper and perform the following steps to create a basic BPEL process:

BPEL is a programming language, and activities provide functions and operations for creating a BPEL process web service. Understanding the purpose and usage of the activities are very important for creating a BPEL process to serve a business function.

In JDeveloper, activities are listed as BPEL constructs and are the building blocks for BPEL processes. Each of the BPEL constructs has the following:

The activities available from Component Pallet located on the right-hand side of the JDeveloper window are shown in the following screenshot:

The main BPEL activities are Receive, Invoke, and Reply. The activities can be added to BPEL by dragging-and-dropping it from the Component Pallet, as shown in the following screenshot:

An example of an activity is Invoke. The Invoke activity is for synchronously, or asynchronously, calling services defined in partner links. For synchronous invocation, specify the input and output variables. Double-click on the Invoke activity after dropping it on the JDeveloper canvas from the Component Pallet to add configuration parameters, as shown in the following screenshot:

The activities within a BPEL process implementation can be categorized as follows:

This following section provides a brief overview and usage of BPEL activities. The activities enable you to perform specific tasks and operations for a BPEL process implementation.

The main steps of a BPEL process are performed by basic activities. The basic activities communicate with web services (receive, invoke, reply), change the content of variables (assign), wait for a certain period (wait), or terminate the process (exit). The following is a brief description of the basic activities:

BPEL provides activities for conditional branching based on data (If-Else), parallel execution (Flow), loop activities (While), way to group activities (Scope), executing activities in parallel (Flow), and selective event processing (Pick). Brief descriptions of the structured activities are listed as follows:

Fault and error handling activity in BPEL allows us to implement the recovery from the runtime errors or business constraints. BPEL provides different fault-handling activities such as Catch, CatchAll, and Throw. Brief descriptions of the fault and error handling activities are listed as follows:

To create BPEL, use either the Synchronous BPEL Process or Asynchronous BPEL Process template from JDeveloper.

The synchronous BPEL default template contains the initial Receive activity and final Reply activity. We can add more activities between Receive and Reply based on the business process and logic. A typical BPEL requires more activities to process the business logic in addition to Receive and Reply activities.

Usually BPEL contains activities such as Assign for copying and manipulating the XML content.

Usually synchronous BPEL processes wait for Reply until processing is complete while the Asynchronous BPEL Process default template contains the initial Receive and Callback activities. One can add more activities between Receive and Callback based on the business process and logic.

The following figure depicts the typical BPEL structure for synchronous and asynchronous BPELs. The client receives the immediate response for a synchronous BPEL and the delayed response for an asynchronous BPEL.

Use synchronous BPEL processes if the BPEL process requires a request-response model. However, creating asynchronous processes is a more flexible and fault-tolerant practice that usually avoids blocking the WebLogic threads.

For asynchronous processes, there is no need to wait for a response before proceeding to the next step. The response can be received as part of a separate process. While creating a BPEL process in JDeveloper, we select either the Synchronous BPEL Process or Asynchronous BPEL Process template based on the design of business process and logic. The following screenshot shows the Design view of JDeveloper for synchronous and asynchronous BPEL processes:

After completing the process, the synchronous BPEL process sends a response back to the client using replyOutput. On the other hand, the asynchronous BPEL process calls back the client with the response message using callBackClient. Synchronous process provides a reply and the asynchronous process needs to implement a callback using the Invoke activity.

Oracle BPEL Process Manager uses the WS-Addressing technique for message correlation between the sender and receiver. In order to correlate the response messages, Oracle BPEL Process Manager simply adds Unique Identifier (UID) in the WS-Addressing headers on the initial request that floats with the simple object access protocol (SOAP) packets. You're not required to take any action as Oracle BPEL Process Manager automatically adds the UID and callback address to correlate the response messages.

The following table explains the major differences between synchronous and asynchronous BPEL processes: