As described in the paper, these services are used by customers/partners to extend and integrate with Oracle Fusion Applications, whether in on-premise or SaaS mode. This post describes the keyword in detail by addressing five frequently asked questions.
Q1. What does the EXTERNAL keyword imply for integration scenarios and SaaS deployments?
To understand this, let’s look at the Fusion Applications deployment topology below Note: this shows only SOA Composite services, but is also applicable for ADF Services.
The topology splits visibility to web and service resources into two categories – internal and external. This is achieved by fronting all HTTP requests through two different Oracle HTTP Servers (OHS), one for internal traffic routed between Fusion Applications servers, and another for external sources, which has only a small subset of the routing rules to prevent unauthorized access by external systems. This approach facilitates unhindered access within the Fusion Applications domain and acts as a firewall to restrict access to external systems.
In the example shown above, internal clients (i.e. those deployed in the same Fusion Applications domain) would have access to all composite services - A, B, and C and any service endpoints that they provide. In contrast, all other external clients are restricted to accessing only services provided through composites A and B.
Another characteristic of services that are exposed externally is that they also enforce a more stringent Oracle Web Services Manager (OWSM) policy using SSL or WS-Security message protection. By contrast, services NOT marked as EXTERNAL are protected using the OWSM Global Policy Attachments (GPA) feature, which in the case of Fusion Apps do not enforce message protection and rely only on username token or SAML identity propagation.
As you may have guessed by now, services tagged with the EXTERNAL keyword in OER, are the only ones provisioned with routing rules on the External OHS and protected with a stringent message protected OWSM policy. This is what makes them suitable for application integration use cases; even more so in the cloud where deploying custom services to the SaaS WebLogic Server domain may not be possible.
Q2. The service I want is not marked as EXTERNAL. Can I just tag it with the keyword for my integration project?
As explained above, making a service “EXTERNAL” is more than just tagging the keyword in OER. The service also needs to be secured using a message protection enabled local OWSM policy and requires modification of the OHS routing rules to allow service URI access to the external world. For Oracle-shipped services, this is done by the Provisioning framework. For custom services, this can be possible in on-premise and hosted installations, but may not be possible in the SaaS mode.
Most likely, if an Oracle-shipped service has not been marked as EXTERNAL, it is due to specific functional and/or security reasons, which is usually not addressable at the customer site.
Q3. If I can’t change non-EXTERNAL services, why document them in OER?
While it is true that non-EXTERNAL services cannot be consumed by external clients, they can still be consumed by internal clients, such as custom implemented composites that are deployed in the Fusion Applications SOA domain in on-premise or hosted deployments. Moreover, apart from service invocations, many composite services also have capabilities for layered customizations for BPEL processes and Oracle Business Rules. The OER entries for these non-EXTERNAL services therefore serve as API documentation.
Q4. Are EXTERNAL services the same as “Public” services?
The two terms — “EXTERNAL” and “Public” — are frequently used interchangeably, however, they are not synonymous! “EXTERNAL” refers to service visibility in the topology, while “Public” basically amounts to the level of API support provided by Oracle. In fact, there is no attribute called “Public”, instead it is referenced by the Compatibility attribute value of Supported.
While most EXTERNAL services tend to be Public, there are exceptions. For instance, mobile-enabled services accessed by iPad or iPhone apps (external to Fusion Applications) will be tagged as EXTERNAL. However, if the only intended supported client is the pre-certified mobile app, then the service may be marked with a Compatibility value of Not Supported to effectively make it “Private”.
The Fusion Applications OER white paper also lists the various combinations of the Keyword and Compatibility tags and their implications for service use in integration projects.
Q5. How do I find all available EXTERNAL services?
Using the cloud hosted OER instance. Simply search for EXTERNAL and limit the Asset Type to ADF Service or Composite Service to filter the results.
IMPORTANT NOTE: This is a simple text search and will result in services that have the word EXTERNAL in any metadata, including descriptions. Therefore, you may get false positives. To confirm the service accessibility, always check the Keyword value on the Taxonomy tab of the service detail page as shown in the screenshot at the top of this post.
Hopefully this post has addressed most of the questions about the EXTERNAL keyword usage. If you still have some, feel free to sound off in the comments.