Java SOA Cookbook

Chapter 10. Advanced Orchestrations with BPEL

Introduction

This chapter picks up right where we left off. Chapter 9 got you going on BPEL basics. You saw how to install a variety of BPEL engines and how to write and deploy basic BPEL orchestrations. But BPEL is a large and complex subject, and in this chapter, we’ll look at some of the more advanced topics, including include parallel execution, timers, correlation, looping, faults, and more. Let’s jump right in.

Executing Activities in Parallel

Problem

You want to execute a set of related activities concurrently.

Solution

Use the BPEL <flow> structured activity.

Discussion

In its simplest form, the <flow> appears much like a <sequence>, in that it is merely a container for other activities that do actual work. The difference is that all of the items specified within the <flow> are executed at roughly the same time. In other words, one does not wait for another to finish, and therefore you cannot treat the result of one operation within a flow as the input to another. Here is an example:

<else> <sequence name="Purchase"> <flow name="SaleCompletedNotifyFlow"> <invoke name="NotifySeller" partnerLink="contactPLink" operation="contactService" portType="ct:contactPortType" inputVariable="ContactServiceIn" outputVariable="ContactServiceOut"/> <invoke name="NotifyShipper" partnerLink="requestShippingPLink" operation="shippingService" portType="shp:shippingPortType" inputVariable="ShippingServiceIn" outputVariable="ShippingerviceOut"/> </flow> <assign ...