In this step, we will implement the BPEL process itself. The goal is to return the book data, including the stock quantity. For this, we would usually need to access the database to query for the stock of the specified book. In our case, we do not want to complicate the example, so we will simply return a fixed value.
To achieve this, we will use the Assign activity to assign a fixed value to a BPEL variable. Assign is one of the basic BPEL activities. We will explain the BPEL language later in this chapter.
For now, let's perform the following steps. First, we will copy BookISSN
from request inputVariable
to response outputVariable
. Second, we will copy a number 5
to the StockQuantity
element of the output message:
BookstoreABPEL
process by selecting the already opened BookstoreABPEL.bpel tab. Alternatively, you can double-click on the BookstoreABPEL
component on the composite design view or double-click on the BookstoreABPEL.bpel
file from the project tree on the left-hand side window.DetermineStockQuantity
. Copy BookISSN
from inputVariable
to outputVariable
by dragging BookISSN
from inputVariable
and dropping it on BookISSN
in outputVariable
, as shown in the following screenshot:StockQuantity
element of the output message, we will need to use an expression. Drag-and-drop Expression from the upper-right corner of the window to the StockQuantity
element. Doing this, the Expression Builder window will appear.5
. This means we need to write number(5)
:We implemented our first BPEL processes. It contains a very simple logic for returning the book data, including the stock quantity. It assigns the book ISSN and the stock quantity to the constant value of 5
. Obviously, this is an oversimplified process, but it is sufficient for our first example and to get a feeling about BPEL. Next, we will try to deploy the BPEL process.