How does Axiom integrate with Apache Axis2 for SOAP message processing?

Axis2 uses Axiom as its sole in-memory representation for SOAP messages - there's no intermediate DOM step - so understanding Axiom is effectively a prerequisite for understanding how a message actually flows through Axis2's engine.

An inbound request is parsed directly into a SOAPEnvelope/SOAPHeader/SOAPBody tree by a StAXSOAPModelBuilder, and that tree becomes part of the MessageContext that gets passed through Axis2's configured phases and handlers.

sequenceDiagram
  participant Client
  participant Transport as Transport Receiver
  participant Builder as StAXSOAPModelBuilder
  participant Phases as Axis2 Phases/Handlers
  participant Service as Message Receiver

  Client->>Transport: Inbound SOAP request (bytes)
  Transport->>Builder: Wrap stream, build SOAPEnvelope lazily
  Builder->>Phases: MessageContext with (partially built) envelope
  Phases->>Phases: Inspect headers (may trigger partial build)
  Phases->>Service: Dispatch to target operation
  Service->>Service: Fully build/deserialize body via databinding

Because the envelope is deferred-built, phases that only need to inspect headers - security, addressing, and dispatch logic, for example - can do their job while triggering only a small amount of materialization, leaving the (potentially large) body untouched until the actual service implementation needs it.

Databinding frameworks used with Axis2, like ADB, can further insert OMSourcedElement-backed content into the body, so that generating the outbound XML from a Java object is itself deferred until the response actually gets serialized onto the wire - extending Axiom's lazy philosophy all the way through both the request and response side of a service invocation.