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API / Swagger Interview questions

What is Swagger Codegen?

Swagger Codegen is a code generation tool that reads an OpenAPI document and produces client-side SDK code, or server-side stub/skeleton code, in any of dozens of supported programming languages, based on templates for each target language.

swagger-codegen generate \
  -i openapi.yaml \
  -l java \
  -o ./generated-client

For client generation, the output is a ready-to-use library with methods matching each API operation, correctly typed request/response models, and handling for authentication schemes defined in the spec — sparing a consuming team from hand-writing that boilerplate and keeping it correct as the API evolves, as long as the client is regenerated when the spec changes.

For server generation, the output is typically a skeleton with routing and method signatures already wired to match the spec, leaving the actual business logic for developers to fill in, which is especially useful in a contract-first workflow where the API shape is agreed upon before any implementation code exists.

What does Swagger Codegen produce from an OpenAPI document?
What must happen when the underlying spec changes for a generated client to stay accurate?

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