What is BPEL and Activities

BPEL Introduction:

Oracle BPEL Process Manager:

 BPEL stands for Business Process Execution Language. It is a XML based declarative language that can be used implement end to end business processes. Basic building block of these processes is a service, which could be a web service. BPEL utilizes various adapters to service enable legacy and custom applications before consuming them in processes. BPEL also provides human workflow that has variety of uses.

BPEL Provide end to end business process by using BPEL activities Like 

Assign activity   2)Switch activity   3)Receive activity   4 )Reply activity

Flow activity      6) FlowN activity   7) Invoke activity     8) Pick activity

Transform        10) Scope activity  11) Email activity     12) Throw activity

Wait activity     14)  While activity  

Assign Activity

This activity provides a method for data manipulation, such as copying the contents of one variable to another. Copy operations enable you to transfer information between variables, expressions, endpoints, and other elements.

Receive Activity

This activity specifies the partner link from which to receive information and the port type and operation for the partner link to invoke. This activity waits for an asynchronous callback response message from a service, such as a loan application approver service. While the BPEL process is waiting, it is dehydrated (compressed and stored) until the callback message arrives. The contents of this response are stored in a response variable in the process.

The receive activity supports the bpelx:property extensions that facilitate the passing of properties through the SOAP header, and the obtaining of SOA runtime system properties for useful information such as tracking.compositeInstanceId and tracking.conversationId.   

Flow Activity

This activity enables you to specify one or more activities to be performed concurrently. A flow activity completes when all activities in the flow have finished processing. Completion of a flow activity includes the possibility that it can be skipped if its enabling condition is false.

For example, assume you use a flow activity to enable two loan offer providers (United Loan service and Star Loan service) to start in parallel. In this case, the flow activity contains two parallel activities – the sequence to invoke the United Loan service and the sequence to invoke the Star Loan service. Each service can take an arbitrary amount of time to complete their loan processes.

FlowN Activity

This activity enables you to create multiple flows equal to the value of N, which is defined at runtime based on the data available and logic within the process. An index variable increments each time a new branch is created, until the index variable reaches the value of N.

Pick Activity

This activity waits for the occurrence of one event in a set of events and performs the activity associated with that event. The occurrence of the events is often mutually exclusive (the process either receives an acceptance or rejection message, but not both). If multiple events occur, the selection of the activity to perform depends on which event occurred first. If the events occur nearly simultaneously, there is a race and the choice of activity to be performed is dependent on both timing and implementation.

Invoke Activity

This activity enables you to specify an operation you want to invoke for the service (identified by its partner link). The operation can be one-way or request-response on a port provided by the service. You can also automatically create variables in an invoke activity. An invoke activity invokes a synchronous web service or initiates an asynchronous web service.

The invoke activity opens a port in the process to send and receive data. It uses this port to submit required data and receive a response. For synchronous callbacks, only one port is needed for both the send and the receive functions.

The invoke activity supports the bpelx:inputProperty and bpelx:outputProperty that facilitate the passing of properties through the SOAP header and the obtaining of SOA runtime system properties for useful information such as the tracking.compositeInstanceId and tracking.conversationId.

Reply Activity

This activity allows the process to send a message in reply to a message that was received through a receive [activity. The combination of a receive activity and a reply activity forms a request-response operation on the WSDL port type for the process

Switch Activity

This activity consists of an ordered list of one or more conditional branches defined in a case branch, followed optionally by an otherwise branch. The branches are considered in the order in which they appear. The first branch whose condition is true is taken and provides the activity performed for the switch. If no branch with a condition is taken, then the otherwise branch is taken. If the otherwise branch is not explicitly specified, then an otherwise branch with an empty activity is assumed to be available. The switch activity is complete when the activity of the selected branch completes.

A switch activity differs in functionality from a flow activity. For example, a flow activity enables a process to gather two loan offers at the same time, but does not compare their values. To compare and make decisions on the values of the two offers, a switch activity is used. The first branch is executed if a defined condition (inside the case branch) is met. If it is not met, the otherwise branch is executed.

Transform Activity

This activity enables you to create a transformation that maps source elements to target elements (for example, incoming purchase order data into outgoing purchase order acknowledgment data).

Figure A-42 shows the Transform dialog in BPEL 1.1. This dialog enables you to perform the following tasks:

Define the source and target variables and parts to map.

Specify the transformation mapper file.

Click the second icon (the Add icon) to the right of the Mapper File field to access the XSLT Mapper for creating a new XSL file for graphically mapping source and target elements. Click the Edit icon (third icon) to edit an existing XSL file.

Figure A-42 Transform Dialog

Compensate Activity

This activity invokes compensation on an inner scope activity that has successfully completed. This activity can be invoked only from within a fault handler or another compensation handler. Compensation occurs when a process cannot complete several operations after completing others. The process must return and undo the previously completed operations. For example, assume a process is designed to book a rental car, a hotel, and a flight. The process books the car and the hotel, but cannot book a flight for the correct day. In this case, the process performs compensation by unbooking the car and the hotel.The compensation handler is invoked with the compensate activity, which names the scope on which the compensation handler is to be invoked.

This activity invokes compensation on an inner scope activity that has successfully completed. This activity can be invo

Scope Activity:

The scope activity partitions a BPEL business process into logically organized sections. It provides context for variables, fault handling, Compensation, event handling, and Correlation sets. It is a structured activity that contains one other activity, which may itself contain other activities.