How do content negotiation and message converters work in Spring MVC?

Connects Content-Type and Accept to handler conditions and converter selection for request reading and response writing.

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Spring MVC uses the request Content-Type to choose a converter that can read the body into the declared Java type. It uses the client's Accept values, the handler's produces condition, and available converters to choose a response representation. If no converter can read the submitted media type, the result is normally 415. If the server cannot produce an acceptable response, the result is normally 406.

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HTTP media semantics, converter capability, 415 and 406 diagnosis, and safe customization.

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Content-Type describes the representation sent; Accept describes representations the client can receive.
Spring MVC uses the request Content-Type to choose a converter that can read the body into the declared Java type. It uses the client's Accept values, the handler's produces condition, and available converters to choose a response representation. If no converter can read the submitted media type, the result is normally 415. If the server cannot produce an acceptable response, the result is normally 406.
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JSON support usually comes from a Jackson converter, while byte arrays, strings, forms, resources, and other media use different converters. A mapping's and conditions participate before controller invocation. I prefer header-based negotiation and explicit API media types over path-extension guessing. When customizing converters, I extend the defaults carefully rather than accidentally replacing standard Boot configuration.

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Treating Content-Type and Accept as the same header.
Calling 415 a JSON validation error.
Replacing all default converters unintentionally.

How do content negotiation and message converters work in Spring MVC?

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