Database Reference
In-Depth Information
Chapter 3. Invoking a BPEL Process
BPEL provides an enterprise and cross-enterprise approach for SOA with simple de-
scriptions of how to orchestrate processes and invoke external programs, applica-
tions, and/or services. In practice, BPEL is actually extending the existing WSDL
standards. WSDL is an XML-based language for describing web services that in-
cludes the details of how to consume them.
BPEL does not replace Java, .NET, or any other programming language, rather it
complements them. In this chapter, we will talk about interoperability between BPEL
and Java. BPEL provides excellent workflow process capabilities; however, one may
find competing arguments from associates that it may not be worth it due to invest-
ments required in learning and using BPEL, additional infrastructure requirements,
and an additional layer for troubleshooting. BPEL won't solve all the enterprise ap-
plications' problems, rather it is a tool to simplify reusability of discrete systems and
facilitate seamless process agility to design and deploy enterprise class composite
applications. The key to success is to realize when and how to use BPEL in imple-
menting composite applications.
Communicating between BPEL to/from
Java
To reuse and integrate applications, one can create web services using XML and
HTTP.
Web Service Description Language
(
WSDL
) is an XML-based language for
describing web services. The web services can be located and invoked over the Web
using WSDL from the service providers.
A WSDL contains an element named
<binding>
which describes how the message
is transmitted on the wire and a
<service>
element that contains the location of the
web service.
The
<portType>
element in WSDL provides a set of operations for the calling cli-
ents. Port type is very similar to the concept of interfaces in Java. Java interface spe-
cifies methods that a calling client can consume but only by specifying a method of
its own. Similarly, Port type in WSDL specifies the operations available that a calling
client can consume but only by specifying an operation of its own.
