RequestBodyParameter

A RequestBodyParameter is a parameter whose value is supplied in the body of an HTTP request. It is used to transmit structured payloads such as JSON or XML and is a common means of sending create, update, or patch data to a web API. This parameter differs from path, query, header, or form parameters, which convey data in the URL or headers or on the request's encoding form.

In many frameworks, the request body is deserialized into a language-native object or data transfer object. The binding process reads the content according to the declared media type (for example, application/json, application/xml) and maps it to a parameter type. Typically, only one body parameter is accepted per endpoint, with additional data provided via query or path parameters.

Validation and constraints: the framework often applies validation rules to the bound object, ensuring required fields, correct formats, and allowed ranges. Documentation or API schemas describe the expected body structure, fields, and examples.

Security and design considerations: trim payloads to necessary fields to reduce risk of overposting, validate ownership and authorization, and enforce content size limits. Using a dedicated DTO can help separate transport concerns from domain models.

In API specifications such as OpenAPI, a body parameter is defined with a schema that describes the expected payload. The term appears in code samples across languages where a function argument is annotated or declared to receive data from the request body.