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SCA in WebSphere Application Server: Overview (deprecated)

Support for Service Component Architecture (SCA) offers a way to construct applications based on Service-Oriented Architecture (SOA). The support uses the Apache Tuscany open-source technology to provide an implementation of the published SCA specifications.

Deprecated feature: 8.5.5.19 or later The Service Component Architecture (SCA) programming model and samples are deprecated, and will be removed in a future release. You cannot deploy new SCA business-level applications.

Update your applications to use different programming models. The programming models that you use vary depending on how you previously incorporated SCA in your application.

If you used SCA for binding, consolidate the ways in which your application is exposed to a few standards, such as Java API for RESTful Web Services (JAX-RS) or Java Message Service (JMS). For example, use JAX-RS for application bindings. To minimize the duplication of binding level implementation, structure your application to use shared code.

If you want to continue to use SCA as part of your long-term strategy, consider hosting your applications on IBM Business Process Manager.

SCA is defined in a set of open specifications produced by IBM® and other industry leaders through the Open SOA Collaboration (OSOA) and OASIS.

You can use SCA to assemble and compose existing services in your enterprise. The key principle of SOA demonstrated by SCA support is the ability to use your existing services to create new ones.

Another key objective of SCA is to highlight the ease-of-use characteristics of SCA service development in Java™. This is accomplished by demonstrating annotated Plain-Old Java-Object (POJO) components deployed using simple JAR packaging schemes, an easy to use assembly model, and wiring abstractions that enable service definition over different transports and protocols.

To learn about SCA in WebSphere® Application Server products, see the following general information:

Benefits of SCA

SCA enables your organization to move quickly into the world of SOA, as follows:

Improve flexibility in application deployment
  • Adapt applications quickly to reflect changes in the business environment
  • Reuse the components you create in other business processes and composite applications
  • Easily compose services into more complex composite applications
  • Adjust solutions to accommodate varying technology offerings (that is, protocols or deployment targets) without the need to rebuild business applications
Increase programmer productivity
  • Stay focused on solving business problems, rather than getting bogged down in the individual complexities of the technologies that connect service consumers and service providers
  • Use the same fundamental principles to uniformly represent existing assets and newly engineered components
  • Organize service components into logical modules to hasten composite application development
  • Leverage the loosely coupled service model with clear service definitions to enable developers to work independently and in parallel, for fast delivery of solutions

OSOA support

SCA in WebSphere Application Server follows the definition of the technology as documented by OSOA. Defining a set of compliance test suites was not part of the OSOA charter, so the implementation provided in this product uses the following specifications as guiding principles. However, IBM provides an implementation that adheres strictly to our interpretation of the specifications.

  • SCA Assembly Model
  • SCA EJB Session Bean Binding
  • SCA Java Component Implementation
  • SCA Java Common Annotations and APIs
  • SCA Java EE Integration
  • SCA JMS Binding
  • SCA Policy Framework
  • SCA Spring Implementation
  • SCA Transaction Policy
  • SCA Web Service Binding

See, Unsupported SCA specifications sections topic for restrictions and limitations that are unsupported.

OASIS support

The product provides partial support for the following Service Component Architecture (SCA) OASIS specifications:

  • OASIS Service Component Architecture / Assembly (SCA-Assembly) 1.1
  • OASIS Service Component Architecture / Policy Framework (SCA-Policy) 1.1

    The product supports OASIS policy attachment, but does not support OASIS policy set definitions.

  • OASIS Service Component Architecture / Bindings (SCA-Bindings) 1.1

    The product supports OASIS SCA JMS Binding 1.1 and OASIS SCA Web Service Binding 1.1, but does not support OASIS SCA JCA Binding 1.1.

  • OASIS Service Component Architecture / J (SCA-J) 1.1

The product supports EJB binding, POJO, JAXB, and SDO as data types.

See, Unsupported SCA specifications sections topic for restrictions and limitations that are unsupported.

Differences between OSOA and OASIS specifications

The OASIS SCA specifications were developed from the OSOA SCA specifications but there are some subtle differences. The following tables list differences between OSOA and OASIS specifications:

Table 1. SCA Assembly Model. Differences between OSOA and OASIS specifications.
Type OSOA OASIS
Namespace https://www.oasis-opencsa.org/sca-assembly http://docs.oasis-open.org/ns/opencsa/sca/200912
XSD   Extensibility removes the occasional UPA issue.

The sca:extensions element appears in various places.
composite.xml Reference targets component/service

Put unconfigured bindings on the reference.

 Reference targets component/service/binding

Do not put unconfigured bindings on the reference. The target string identifies them and the configuration is pulled from the service.
Asynchronous invocation Not supported Asynchronous invocation is supported. Activate it by including the asyncInvocation intent on an interface (or service or reference).
Conversations Supported Not supported
Operation configuration Supported in services or references Not supported in services or references
Interface Cannot be marked remotable from within the composite Can be marked as remotable from within the composite
Wire format   Bindings can have a wireFormat child element
Operation selector   Bindings can have an operationSelector child element
Wires   New replace semantics
Domain level   References and services are ignored
definitions.xml Has binding element Does not have binding element
Table 2. SCA Java API and Annotations. Differences between OSOA and OASIS specifications.
Type OSOA OASIS
API   SCA Client API
API Has CallableReferences Does not have CallableReferences. Has ServiceReference.
API   New exceptions: InvalidServiceException, NoSuchDomainException, NoSuchServiceException
API Has conversion APIs Does not have conversion APIs
Annotations   Has AsyncInvocation. Does not have conversations.

Differences between OSOA and OASIS in SCA applications

  • You can distinguish between OSOA and OASIS composites by looking at the SCA artifact XML namespaces.
    In an OSOA composite description, the namespace resembles:
    <composite xmlns=http://docs.oasis-open.org/ns/opencsa/sca/200912 ...>
...
</composite>
    In an OASIS composite description, the namespace resembles:
    <composite xmlns=http://www.osoa.org/xmlns/sca/1.0 ...>
...
</composite>
  • You cannot mix OSOA and OASIS SCA artifacts, such as .composite files or sca-contribution.xml files, within the same asset. However you can wire OSOA and OASIS SCA components together when both SCA composites are running in a single cell.

    For OSOA, an sca-contribution.xml file is not required if there is only one default.composite file in the Java archive (JAR). An sca-contribution.xml file can reside in the META-INF/ directory or in a subdirectory.

    For OASIS, an sca-contribution.xml file is required and must reside in the META-INF/ directory, and not in a subdirectory.

WebSphere support for SCA

As already noted, multiple specifications are defined at OSOA and OASIS, as well as Tuscany extensions provided in open source that go beyond the basic mission of WebSphere Application Server. Each vendor can decide which aspects of SCA apply to their product. For WebSphere Application Server, the focus is on enabling compositions as services, Java components, and integration of key qualities of service-like transactions and security.

SCA can enable mediations, business rules, and business process execution language to be treated as any other service, and while WebSphere Application Server provides the mechanisms to wire services that are implemented in those languages and environments, the product does not provide native support to host those kinds of service implementations.

SCA support includes the following:
  • POJO (Plain Old Java Object) service-component implementations, including support for annotations
  • Asynchronous capability
  • Recursive composition model support
  • Support for SCA specifications
  • Support for SCA services developed from existing WSDL files or Java code
  • Deployment of SCA composites in business-level applications
  • SCA authorization and security identity policies
  • PassByReference optimization for SCA applications
  • Several binding types, including web services binding, SCA default binding, Enterprise JavaBeans (EJB), Java Message Service (JMS), Atom, and HTTP bindings
  • Support for Java Architecture for XML Binding (JAXB) data bindings in SCA applications
  • SCA annotations for Java Platform, Enterprise Edition (Java EE) web modules, session beans, and message-driven beans
  • Preview of native SCA deployment
  • Spring 2.5.5 containers in SCA applications
  • OSGi applications as SCA implementations
  • Service Data Objects 2.1.1
  • Sample SCA composites compiled specifically for use with the product