The Service Gateway is a mediation-module pattern (Integration Designer / WebSphere ESB, BAW Advanced) that exposes one generic entry point for many services: the gateway's interface is a generic anyType / xsd:any operation, the mediation flow looks at the incoming message (operation name, SOAPAction, a header, the root element) and routes it dynamically to the real service - transforming, logging, checking security and applying policies on the way. Clients call the gateway with any WSDL-conformant message; the gateway needs no change when a new back-end service is added, only a routing rule.
- Built from the Service Gateway export type (the SCA export with a generic interface) + a mediation flow with Message Filter / Endpoint Lookup (registry-based routing, e.g. WSRR) / Service Invoke primitives + XSL Transformation for canonical formats.
- Variants: static gateway (routing table in the flow), dynamic gateway (endpoint lookup in a registry), proxy gateway (one gateway per external partner for security and throttling).
- Typical uses: a single façade for BPM to call every legacy system (the BPD's AIS points at the gateway), protocol bridging (SOAP to MQ), versioning (route v1 clients to a compatibility transform), central logging / auditing of integration traffic.
Outside BAW Advanced the same role is played by an API gateway (IBM API Connect, DataPower) or App Connect Enterprise flows; when designing new integrations for CP4BA, put the gateway in ACE / API Connect and let BAW call REST operations behind it.
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