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SCA in WebSphere Application Server: Overview

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.

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

Use SCA to assemble and compose existing services in our enterprise. The key principle of SOA demonstrated by SCA support is the ability to use the 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 we 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.

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


OASIS support

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New feature:

v8.5 adds support for the Service Component Architecture (SCA) OASIS programming model implementation.newfeat

The product provides partial support for the following SCA OASIS specifications:

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

See the "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:

Type OSOA OASIS
Namespace http://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

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


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 WAS. 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:


Related concepts

  • Unsupported SCA specification sections
  • SCA components
  • SCA composites
  • SCA contributions
  • SCA domain


    Related tasks

  • Develop SCA services from existing WSDL files
  • Develop SCA services with existing Java code
  • Develop SCA service clients
  • Specify bindings in an SCA environment
  • Use JAXB for XML data binding
  • Use existing Java EE modules and components as SCA implementations
  • Use Spring 2.5.5 containers in SCA applications
  • Use SCA authorization and security identity policies
  • Use PassByReference optimization in SCA applications
  • Deploy and administering business-level applications

  • Specifications and API documentation


    Related information:

    Samples, v8.5 information center