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🧩 SOA (Service-Oriented Architecture)

✅ Overview​

A service splitting approach prior to Microservices, building enterprise systems as a collection of "Services".

✅ Problems Addressed​

  • Systems within an enterprise become silos and cannot cooperate.
  • Cooperation without integration infrastructure (ESB) is extremely difficult.
  • Want to standardize heavy enterprise integration.

✅ Basic Philosophy & Rules​

  • Integration by ESB (Enterprise Service Bus).
  • Strict contract by SOAP / WSDL / XML.
  • Service catalog management.
  • Governance-oriented design.

Conceptual Diagram​

✅ Suitable Applications​

  • Integration of mission-critical systems in large enterprises.
  • Long-term stable operation of business processes.
  • Areas with low change frequency and strong governance.

❌ Unsuitable Cases​

  • Fast-changing Web products.
  • Areas where development speed and flexibility are important.
  • Cases where lightweight API (REST/gRPC) is sufficient.

✅ History​

  • Spread as the center of enterprise IT in the 2000s.
  • Lightweighting advanced by REST / Microservices, currently continuing in limited areas.

✅ Related Styles​

  • Microservices: Developed as a lightweight version of SOA.
  • API Gateway: Corresponds as a modern version of SOA's "Entrance".

✅ Representative Frameworks​

  • Oracle SOA Suite / IBM WebSphere ESB
    SOA platforms used for a long time in enterprise IT.

  • Middleware supporting WS-* (SOAP / WSDL)
    Communication infrastructure supporting SOA standards at that time.

  • BizTalk Server
    SOA implementation for enterprise integration.

✅ Design Patterns Supporting This Style​

  • Facade
    ESB functions as the entrance of the entire service.

  • Mediator
    ESB mediates cooperation between multiple systems.

  • Adapter
    Essential when wrapping legacy systems with SOAP/WSDL.

  • Proxy
    Message validation / Security application.

✅ Summary​

SOA remains important in the context of Enterprise IT,
and is an architecture specialized for high-governance areas such as finance and mission-critical systems.