このページは、まだ日本語ではご利用いただけません。翻訳中です。
古いプラグインバージョンのドキュメントを閲覧しています。
Using templates as values
You can use any of the current request headers, query parameters, captured URI groups, and shared variables as templates to populate supported config fields.
Request Parameter | Template |
---|---|
header |
$(headers.<header-name>) or $(headers["<header-name>"]) ) |
querystring |
$(query_params.<query-param-name>) or $(query_params["<query-param-name>"]) ) |
captured URIs |
$(uri_captures.<group-name>) or $(uri_captures["<group-name>"]) ) |
shared variables |
$(shared.<variable-name>) or $(shared["<variable-name>"]) ) |
To escape a template, wrap it inside quotes and pass inside another template. For example:
$('$(something_that_needs_to_escaped)')
Note: The plugin creates a non-mutable table of request headers, query strings, and captured URIs before transformation. So any update or removal of parameters used in the template does not affect the rendered value of template.
Arrays and nested objects
The plugin allows navigating complex JSON objects (arrays and nested objects)
when config.dots_in_keys
is set to false
(the default is true
).
-
array[*]
: Loops through all elements of the array. -
array[N]
: Navigates to the nth element of the array (the index of the first element is1
). -
top.sub
: Navigates to thesub
property of thetop
object.
These can be combined. For example, config.remove.json: customers[*].info.phone
removes
all phone
properties from inside the info
object of all entries in the customers
array.
Advanced templates
The content of the placeholder $(...)
is evaluated as a Lua expression, so
logical operators may be used. For example:
Header-Name:$(uri_captures["user-id"] or query_params["user"] or "unknown")
This will first look for the path parameter named user-id
(in uri_captures
). If not found, it will
return the query parameter named user
. If that also doesn’t exist, it returns the default
value ‘“unknown”’.
Constant parts can be specified as part of the template outside the dynamic
placeholders. For example, creating a basic-auth header from a query parameter
called auth
that only contains the base64-encoded part:
Authorization:Basic $(query_params["auth"])
Lambdas are also supported if wrapped as an expression like this:
$((function() ... implementation here ... end)())
A complete lambda example for prefixing a header value with “Basic “ if not already there:
Authorization:$((function()
local value = headers.Authorization
if not value then
return
end
if value:sub(1, 6) == "Basic " then
return value -- was already properly formed
end
return "Basic " .. value -- added proper prefix
end)())
Note: Especially in multi-line templates like the example above, make sure not to add any trailing white-space or new-lines. Since these would be outside the placeholders, they would be considered part of the template, and hence would be appended to the generated value.
The environment is sandboxed, meaning that Lambda’s will not have access to any
library functions, except for the string methods (like sub()
in the example
above).
Examples using template as value
-
Add a service named
test
which routes requests to the httpbin.konghq.com upstream service:curl -X POST http://localhost:8001/services \ --data 'name=test' \ --data 'url=https://httpbin.konghq.com/anything'
-
Create a route for the
test
service, capturing auser_id
field from the third segment of the request path using a regex:Kubernetes users: Version
v1beta1
of the Ingress specification does not allow the use of named regex capture groups in paths. If you use the ingress controller, you should use unnamed groups, e.g.(\w+)/
instead of(?<user_id>\w+)
. You can access these based on their order in the URL path. For example$(uri_captures[1])
obtains the value of the first capture group.curl -X POST http://localhost:8001/services/test/routes --data "name=test_user" \ --data-urlencode 'paths=~/requests/user/(?<user_id>\w+)'
You can learn more about using regexes in paths in the Kong Gateway traffic routing reference.
-
Enable the
request-transformer-advanced
plugin to add a new header,x-user-id
, whose value is being set from the captured group in the route path specified above:curl -XPOST http://localhost:8001/routes/test_user/plugins --data "name=request-transformer-advanced" --data "config.add.headers=x-user-id:\$(uri_captures['user_id'])"
-
Now send a request with a user id in the route path:
curl -i -X GET localhost:8000/requests/user/foo
You should notice in the response that the
x-user-id
header has been added with a value offoo
.