Databases Reference
In-Depth Information
The workflow services have documented APIs, so they can be invoked just like any
other web service. We take advantage of these APIs to build the order management
business service and look at how to do this as part of
Chapter 17
,
Workflow Patterns
.
External web services
oBay makes use of a number of "simulated" real world web services, which are
invoked via OSB. A key consideration when using external web services is what
happens if they fail. We look at this as part of
Chapter 14
,
Error Handling
.
oBay developed services
As oBay is a start-up, it has rather limited inhouse applications, so we are going to
build most of these services from scratch. The great thing about SOA is that we can
actually build these application services using whichever technology is appropriate,
for example, Java or PL/SQL.
One option is to use Oracle ADF business components, which can be used to
implement Service Data Objects, a new feature in 11gR1. We cover this in detail
in
Chapter 12
,
Building Entity Services using Service Data Objects (SDOs)
.
oBay internal virtual services
All of our oBay developed application services have a straight one-to-one mapping
with a corresponding virtual service. This is quite common when developing the
underlying application services as part of the overall implementation.
When exposing functionality from existing systems, this won't always be the case.
For example, you may have multiple systems performing the same function. In this
scenario, multiple application services would map to a single virtual service, which
would be responsible for routing requests to the appropriate system. This is the case
for our external services, where we have multiple services for address and credit
card services.
oBay business services
At first glance, this looks pretty unremarkable. However, there are a few areas worth
further scrutiny. Many of the task-based services, such as
UserManagement
, are built
using one or more entity services and do little more than layer validation on top. We
examine this approach in
Chapter 13
,
Building Validation into Services
.
