Error 400: Input is invalid JSON when making certain requests from Swagger UI

Issue

When you execute a PUT method from the Swagger UI, such as (this is the request generated from the UI):

url -X 'PUT' \
  'http://localhost:8080/o/headless-delivery/v1.0/documents/183873/permissions' \
  -H 'accept: application/json' \
  -H 'Content-Type: */*' \
  -H 'x-csrf-token: a5GuDT5U' \
  -d '[
  {
    "actionIds": [
      "UPDATE",
      "VIEW"
    ],
    "roleName": "Site Member"
  }
]'

You get the following 400 response status even though the JSON is correct:

{
  "status": "BAD_REQUEST",
  "title": "Input is invalid JSON"
}

Environment

Liferay DXP 7.4

Resolution

This happens because an existing bug in the Swagger UI, which does not generate the Content-Type correctly. It will be fixed in https://issues.liferay.com/browse/LPS-163167

The current workaround is to use a tool like Postman to make the request, defining the Content-Type header as application/json:

curl -X 'PUT' \
  'http://localhost:8080/o/headless-delivery/v1.0/documents/43919/permissions' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json' \
  -u 'test@liferay.com:test' \
  -d '[
  {
    "actionIds": [
      "UPDATE",
      "VIEW"
    ],
    "roleName": "Site Member"
  }