Java Reference
In-Depth Information
To achieve this end, most ESBs offer support for invoking web services and other network-
ready application nodes, employ adapters to connect with packaged and legacy applications,
offer robust routing support for messages, allow orchestration and transformation of message
content, and more.
NOTE
As mentioned previously, any given product calling itself an ESB may not have all of these features.
However, many ESBs have all of them and may also include additional capabilities.
Let's look more closely at each of these features.
Web services support
ESBs offer the ability to invoke SOAP- and WSDL-based web services, as well as POX (Plain
Old XML) services over HTTP. In general, you use a design-time tool to create a proxy WSDL
to a web service that you want to expose on the ESB. Instead of connecting directly to your
web service WSDL, clients connect to the WSDL exposed by the bus. This allows you to cre-
ate a small connector that executes within the bus that includes your routing or transformation
logic. Different ESBs handle this connector portion very differently, which is one reason this
chapter is structured the way it is. For example, OpenESB (soon to be renamed GlassfishESB)
handles this entirely through BPEL. The Oracle Service Bus has you create a “route” in their
Eclipse-based tool, and you can add rules and message enhancements within the route. You
can then publish the route to your enterprise repository.
In general, ESBs indicate support for REST simply as the ability to invoke an endpoint URI
with an XML message.
Adapters
For applications that do not directly have a SOAP or XML interface, many vendors will
provide adapters (often at additional cost) that allow you to integrate specifically with differ-
ent third-party ERP, databases, or other packaged systems, such as PeopleSoft, SAP R/3, and
Siebel. Adapters typically exist for relational databases, file interfaces, and so forth.
Many packaged applications, such as PeopleSoft, expose lots of their functionality as web ser-
vices. But you may have customized certain aspects of the application, or want to connect
with it in a way not provided by their XML services. Adapters also allow you to avoid paying
for runtime translation to and from XML if the system supports direct object serialization. So
adapters can be a good option even in these cases.
