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28 lines
1.5 KiB
Markdown
28 lines
1.5 KiB
Markdown
# Content Negotiation
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Every API **MUST** implement and every API Consumer **MUST** use the [HTTP content negotiation](https://tools.ietf.org/html/rfc7231#section-3.4) where a representation of a resource is requested.
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> NOTE: The content negotiation plays the key role in evolving an API, **change management and versioning**.
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#### Example
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A client is programmed to understand the `application/vnd.example.resource+json; version=2` message format semantics. The client requests a representation of the `/greeting` resource in desired the media type (including its version) from the server:
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```
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GET /greeting HTTP/1.1
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Accept: application/vnd.example.resource+json; version=2
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...
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```
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The server is able to provide only a newer version of the requested media type `version=2.1.3`. But since the newer version is backward compatible with the requested `version=2` (related: Changes & Versioning) it is able to satisfy the request and responds:
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```
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HTTP/1.1 200 OK
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Content-Type: application/vnd.example.resource+json; version=2.1.3
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...
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```
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> NOTE: A server that doesn't have the requested representation media type available MUST respond with the HTTP Status Code **406 Not Acceptable**.
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>
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> NOTE: A server MAY have multiple choices available and MAY respond with the **300 Multiple Choices** response. In which case client SHOULD choose from the presented choices.
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>
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> You can read more about content negotiation at [MDN Content negotiation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Content_negotiation).
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