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Looking for the plugin's configuration parameters? You can find them in the Response Transformer Advanced configuration reference doc.
Transform the response sent by the upstream server on the fly before returning the response to the client.
The Response Transformer Advanced plugin is a superset of the open-source Response Transformer plugin.
The advanced plugin adds the following abilities:
- When transforming a JSON payload, transformations are applied to nested JSON objects and
arrays. This can be turned off and on using the
config.dots_in_keys
configuration parameter. See Response Transformer Advanced arrays and nested objects. - Transformations can be restricted to responses with specific status codes using various
config.*.if_status
configuration parameters. - JSON body contents can be restricted to a set of allowed properties with
config.allow.json
. - The entire response body can be replaced using
config.replace.body
. - Arbitrary transformation functions written in Lua can be applied.
- The plugin will decompress and recompress Gzip-compressed payloads
when the
Content-Encoding
header isgzip
.
Notes:
- Transformations on the response body can cause changes in performance. To parse and modify a JSON body, the plugin needs to retain it in memory, which might cause pressure on the worker’s Lua VM when dealing with large bodies (several MB). Because of Nginx’s internals, the
Content-Length
header will not be set when transforming a response body.- If the value contains a
,
then the comma separated format for lists cannot be used. Array notation must be used instead.
Order of execution
The plugin performs the response transformation in the following order:
remove –> replace –> add –> append
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.
Examples
In these examples, the plugin is enabled on a Route. This would work similarly for Services.
- Add multiple headers by passing each
header:value
pair separately:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.add.headers[1]=h1:v1" \
--data "config.add.headers[2]=h2:v1"
upstream response headers | proxied response headers |
---|---|
h1: v1 |
|
- Add multiple headers by passing comma-separated
header:value
pair:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.add.headers=h1:v1,h2:v2"
upstream response headers | proxied response headers |
---|---|
h1: v1 |
|
- Add multiple headers passing config as a JSON body:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--header 'content-type: application/json' \
--data '{"name": "response-transformer-advanced", "config": {"add": {"headers": ["h1:v2", "h2:v1"]}}}'
upstream response headers | proxied response headers |
---|---|
h1: v1 |
|
- Add a body property and a header:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.add.json=p1:v1,p2=v2" \
--data "config.add.headers=h1:v1"
upstream response headers | proxied response headers |
---|---|
h1: v2 |
|
h3: v1 |
|
upstream response JSON body | proxied response body |
---|---|
{} | {“p1” : “v1”, “p2”: “v2”} |
{“p1” : “v2”} | {“p1” : “v2”, “p2”: “v2”} |
- Append multiple headers and remove a body property:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--header 'content-type: application/json' \
--data '{"name": "response-transformer-advanced", "config": {"append": {"headers": ["h1:v2", "h2:v1"]}, "remove": {"json": ["p1"]}}}'
upstream response headers | proxied response headers |
---|---|
h1: v1 |
|
upstream response JSON body | proxied response body |
---|---|
{“p2”: “v2”} | {“p2”: “v2”} |
{“p1” : “v1”, “p2” : “v1”} | {“p2”: “v2”} |
- Replace entire response body if response code is 500:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.replace.body='{\"error\": \"internal server error\"}'" \
--data "config.replace.if_status=500"
Note: The plugin doesn’t validate the value in config.replace.body
against
the content type as defined in the Content-Type
response header.
- Remove nested JSON content:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.remove.json=customers.info.phone" \
--data "config.dots_in_keys=false"
When dots_in_keys
is false
, the customers.info.phone
value is interpreted as
nested JSON objects. When dots_in_keys
is true
(default), customers.info.phone
is
treated as a single property.
- Perform arbitrary transforms to a JSON body
Use the power of embedding Lua to perform arbitrary transformations on JSON bodies. Transformation functions receive an argument with the JSON body, and must return the transformed response body:
-- transform.lua
-- this function transforms
-- { "foo": "something", "something": "else" }
-- into
-- { "foobar": "hello world", "something": "else" }
return function (data)
if type(data) ~= "table" then
return data
end
-- remove foo key
data["foo"] = nil
-- add a new key
data["foobar"] = "hello world"
return data
end
curl -X POST http://localhost:8001/routes/{route id}/plugins \
-F "name=response-transformer-advanced" \
-F "config.transform.functions=@transform.lua" \
-F "config.transform.if_status=200"
- Remove the entire header field with a given header name:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.remove.headers=h1,h2"
upstream response headers | proxied response headers |
---|---|
h1:v1,v2,v3 | {} |
h2:v2 | {} |
- Remove a specific header value of a given header field:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.remove.headers=h1:v1,h1:v2"
upstream response headers | proxied response headers |
---|---|
h1:v1,v2,v3 | h1:v3 |
- Remove a specific header value from a comma-separated list of header values:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.remove.headers=h1:v1,h1:v2"
upstream response headers | proxied response headers |
---|---|
h1:v1,v2,v3 | h1:v3 |
Note: The plugin doesn’t remove header values if the values are not separated by commas, unless it’s a Set-Cookie
header field
(as specified in RFC 7230).
- Remove a specific header value defined by a regular expression
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.remove.headers=h1:/JSESSIONID=.*/, h2://status/$/"
upstream response headers | proxied response headers |
---|---|
h1:JSESSIONID=1876832,path=/ | h1:path=/ |
h2:/match/status/,/status/no-match/ | h2:/status/no-match/ |
- Explicitly set the type of the added JSON value
-1
to be anumber
(instead of the implicitly inferred typestring
) if the response code is 500:
curl -X POST http://localhost:8001/routes/{route id}/plugins \
--data "name=response-transformer-advanced" \
--data "config.add.json=p1:-1" \
--data "config.add.json_types=number" \
--data "config.add.if_status=500"