How does one input become two processing paths?

Goal & mental model verified

Spring Integration models messages passing through channels and endpoints. Adapters connect external systems; transformers change representation; routers select destinations. Channel type affects threading and delivery behavior.

Worked example · design exercise synthesis

An inbound insurer file adapter emits messages. A transformer normalizes records; a router sends valid records to underwriting and malformed ones to a review destination.

Engineering decision synthesis

Use integration flows when multiple protocols and routing rules need explicit composition. Prefer a direct service call for a simple local interaction; each extra channel adds behavior to understand.

Pitfall & diagnosis synthesis

Assuming every channel is asynchronous misreads the execution model. A slow endpoint can block a synchronous flow; unbounded asynchronous handoff can merely move overload into memory.

Improve & validate synthesis

Choose and document channel capacity and error handling. Simulate slow consumers and malformed messages; inspect queue depth, rejection behavior and recovery ownership.