If you're talking about header parameters sent by consumer when calling the API...
You can at least define them once and for all in parameters sections then only reference them when needed. In the example below:
CommonPathParameterHeader
,ReusableParameterHeader
andAnotherReusableParameterHeader
are defined once and for all inparameters
on the root of the document and can be used in any parameters listCommonPathParameterHeader
is referenced inparameters
section of/resources
and/other-resources
paths, meaning that ALL operation of these paths need this headerReusableParameterHeader
is referenced inget /resources
meaning that it's needed on this operation- Same thing for
AnotherReusableParameterHeader
inget /other-resources
Example:
swagger: '2.0'
info:
version: 1.0.0
title: Header API
description: A simple API to learn how you can define headers
parameters:
CommonPathParameterHeader:
name: COMMON-PARAMETER-HEADER
type: string
in: header
required: true
ReusableParameterHeader:
name: REUSABLE-PARAMETER-HEADER
type: string
in: header
required: true
AnotherReusableParameterHeader:
name: ANOTHER-REUSABLE-PARAMETER-HEADER
type: string
in: header
required: true
paths:
/resources:
parameters:
- $ref: '#/parameters/CommonPathParameterHeader'
get:
parameters:
- $ref: '#/parameters/ReusableParameterHeader'
responses:
'200':
description: gets some resources
/other-resources:
parameters:
- $ref: '#/parameters/CommonPathParameterHeader'
get:
parameters:
- $ref: '#/parameters/AnotherReusableParameterHeader'
responses:
'200':
description: gets some other resources
post:
responses:
'204':
description: Succesfully created.
If you're talking about header sent with each API response...
Unfortunately you cannot define reusable response headers. But at least you can define a reusable response containing these headers for common HTTP responses such as a 500 error.
Example:
swagger: '2.0'
info:
version: 1.0.0
title: Header API
description: A simple API to learn how you can define headers
parameters:
CommonPathParameterHeader:
name: COMMON-PARAMETER-HEADER
type: string
in: header
required: true
ReusableParameterHeader:
name: REUSABLE-PARAMETER-HEADER
type: string
in: header
required: true
AnotherReusableParameterHeader:
name: ANOTHER-REUSABLE-PARAMETER-HEADER
type: string
in: header
required: true
paths:
/resources:
parameters:
- $ref: '#/parameters/CommonPathParameterHeader'
get:
parameters:
- $ref: '#/parameters/ReusableParameterHeader'
responses:
'200':
description: gets some resources
headers:
X-Rate-Limit-Remaining:
type: integer
X-Rate-Limit-Reset:
type: string
format: date-time
/other-resources:
parameters:
- $ref: '#/parameters/CommonPathParameterHeader'
get:
parameters:
- $ref: '#/parameters/AnotherReusableParameterHeader'
responses:
'200':
description: gets some other resources
headers:
X-Rate-Limit-Remaining:
type: integer
X-Rate-Limit-Reset:
type: string
format: date-time
post:
responses:
'204':
description: Succesfully created.
headers:
X-Rate-Limit-Remaining:
type: integer
X-Rate-Limit-Reset:
type: string
format: date-time
'500':
$ref: '#/responses/Standard500ErrorResponse'
responses:
Standard500ErrorResponse:
description: An unexpected error occured.
headers:
X-Rate-Limit-Remaining:
type: integer
X-Rate-Limit-Reset:
type: string
format: date-time
About OpenAPI (fka. Swagger) Next version
The OpenAPI spec (fka. Swagger) will evolve and include the definition of reusable response headers among other things (cf. https://github.com/OAI/OpenAPI-Specification/issues/563).