Response Transformer Advanced plugin

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, and provides additional features:

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 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 is gzip.

Response Transformer Advanced includes the following additional configurations: add.if_status, append.if_status, remove.if_status, replace.body, replace.if_status, transform.functions, transform.if_status, allow.json, rename.if_status, transform.json, and dots_in_keys.

Note on transforming bodies: Be aware of the performance of transformations on the response body. In order 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 MBs). Because of Nginx's internals, the Content-Length header will not be set when transforming a response body.

Configuration Reference

This plugin is compatible with DB-less mode.

In DB-less mode, you configure Kong Gateway declaratively. Therefore, the Admin API is mostly read-only. The only tasks it can perform are all related to handling the declarative config, including:

Setting a target's health status in the load balancer
Validating configurations against schemas
Uploading the declarative configuration using the /config endpoint

Enable the plugin on a service

Admin API

Kubernetes

Declarative (YAML)

Kong Manager

For example, configure this plugin on a service by making the following request:

curl -X POST http://{HOST}:8001/services/{SERVICE}/plugins \
    --data "name=response-transformer-advanced"  \
    --data "config.remove.headers=x-toremove" \
    --data "config.remove.headers=x-another-one:application/json" \
    --data "config.remove.headers=x-list-of-values:v1,v2,v3" \
    --data "config.remove.headers=Set-Cookie:/JSESSIONID=.*/" \
    --data "config.remove.headers=x-another-regex://status/$/" \
    --data "config.remove.headers=x-one-more-regex:/^/begin//" \
    --data "config.remove.json=json-key-toremove" \
    --data "config.remove.json=another-json-key" \
    --data "config.add.headers=x-new-header:value" \
    --data "config.add.headers=x-another-header:something" \
    --data "config.add.json=new-json-key:some_value" \
    --data "config.add.json=another-json-key:some_value" \
    --data "config.add.json_types=new-json-key:string" \
    --data "config.add.json_types=another-json-key:boolean" \
    --data "config.add.json_types=another-json-key:number" \
    --data "config.append.headers=x-existing-header:some_value" \
    --data "config.append.headers=x-another-header:some_value"

SERVICE is the id or name of the service that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <response-transformer-advanced-example>
config: 
  remove:
    headers:
    - x-toremove
    - x-another-one:application/json
    - x-list-of-values:v1,v2,v3
    - Set-Cookie:/JSESSIONID=.*/
    - x-another-regex://status/$/
    - x-one-more-regex:/^/begin//
  remove:
    json:
    - json-key-toremove
    - another-json-key
  add:
    headers:
    - x-new-header:value
    - x-another-header:something
  add:
    json:
    - new-json-key:some_value
    - another-json-key:some_value
  add:
    json_types:
    - new-json-key:string
    - another-json-key:boolean
    - another-json-key:number
  append:
    headers:
    - x-existing-header:some_value
    - x-another-header:some_value
plugin: response-transformer-advanced

Next, apply the KongPlugin resource to a Service by annotating the Service as follows:

apiVersion: v1
kind: Service
metadata:
  name: {SERVICE}
  labels:
    app: {SERVICE}
  annotations:
    konghq.com/plugins: <response-transformer-advanced-example>
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: {SERVICE}
  selector:
    app: {SERVICE}

{SERVICE} is the id or name of the service that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

For example, configure this plugin on a service by adding this section to your declarative configuration file:

plugins:
- name: response-transformer-advanced
  service: {SERVICE}
  config: 
    remove:
      headers:
      - x-toremove
      - x-another-one:application/json
      - x-list-of-values:v1,v2,v3
      - Set-Cookie:/JSESSIONID=.*/
      - x-another-regex://status/$/
      - x-one-more-regex:/^/begin//
    remove:
      json:
      - json-key-toremove
      - another-json-key
    add:
      headers:
      - x-new-header:value
      - x-another-header:something
    add:
      json:
      - new-json-key:some_value
      - another-json-key:some_value
    add:
      json_types:
      - new-json-key:string
      - another-json-key:boolean
      - another-json-key:number
    append:
      headers:
      - x-existing-header:some_value
      - x-another-header:some_value

SERVICE is the id or name of the service that this plugin configuration will target.

Configure this plugin on a service:

In Kong Manager, select the workspace.
From the Dashboard, scroll down to Services and click View for the service row.
Scroll down to plugins and click Add Plugin.
Find and select the Response Transformer Advanced plugin.

Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
If the option is available, select Scoped.
Add the service name and ID to the Service field if it is not already prefilled.
Click Create.

Enable the plugin on a route

Admin API

Kubernetes

Declarative (YAML)

Kong Manager

For example, configure this plugin on a route with:

$ curl -X POST http://{HOST}:8001/routes/{ROUTE}/plugins \
    --data "name=response-transformer-advanced"  \
    --data "config.remove.headers=x-toremove" \
    --data "config.remove.headers=x-another-one:application/json" \
    --data "config.remove.headers=x-list-of-values:v1,v2,v3" \
    --data "config.remove.headers=Set-Cookie:/JSESSIONID=.*/" \
    --data "config.remove.headers=x-another-regex://status/$/" \
    --data "config.remove.headers=x-one-more-regex:/^/begin//" \
    --data "config.remove.json=json-key-toremove" \
    --data "config.remove.json=another-json-key" \
    --data "config.add.headers=x-new-header:value" \
    --data "config.add.headers=x-another-header:something" \
    --data "config.add.json=new-json-key:some_value" \
    --data "config.add.json=another-json-key:some_value" \
    --data "config.add.json_types=new-json-key:string" \
    --data "config.add.json_types=another-json-key:boolean" \
    --data "config.add.json_types=another-json-key:number" \
    --data "config.append.headers=x-existing-header:some_value" \
    --data "config.append.headers=x-another-header:some_value"

ROUTE is the id or name of the route that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <response-transformer-advanced-example>
config: 
  remove:
    headers:
    - x-toremove
    - x-another-one:application/json
    - x-list-of-values:v1,v2,v3
    - Set-Cookie:/JSESSIONID=.*/
    - x-another-regex://status/$/
    - x-one-more-regex:/^/begin//
  remove:
    json:
    - json-key-toremove
    - another-json-key
  add:
    headers:
    - x-new-header:value
    - x-another-header:something
  add:
    json:
    - new-json-key:some_value
    - another-json-key:some_value
  add:
    json_types:
    - new-json-key:string
    - another-json-key:boolean
    - another-json-key:number
  append:
    headers:
    - x-existing-header:some_value
    - x-another-header:some_value
plugin: response-transformer-advanced

Then, apply it to an ingress (Route or Routes) by annotating the ingress as follows:

apiVersion: networking/v1beta1
kind: Ingress
metadata:
  name: {ROUTE}
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: <response-transformer-advanced-example>
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          serviceName: echo
          servicePort: 80

ROUTE is the id or name of the route that this plugin configuration will target.

For example, configure this plugin on a route by adding this section to your declarative configuration file:

plugins:
- name: response-transformer-advanced
  route: <route>
  config: 
    remove:
      headers:
      - x-toremove
      - x-another-one:application/json
      - x-list-of-values:v1,v2,v3
      - Set-Cookie:/JSESSIONID=.*/
      - x-another-regex://status/$/
      - x-one-more-regex:/^/begin//
    remove:
      json:
      - json-key-toremove
      - another-json-key
    add:
      headers:
      - x-new-header:value
      - x-another-header:something
    add:
      json:
      - new-json-key:some_value
      - another-json-key:some_value
    add:
      json_types:
      - new-json-key:string
      - another-json-key:boolean
      - another-json-key:number
    append:
      headers:
      - x-existing-header:some_value
      - x-another-header:some_value

ROUTE is the id or name of the route that this plugin configuration will target.

Configure this plugin on a route:

In Kong Manager, select the workspace.
From the Dashboard, select Routes in the left navigation.
Click View for the route row.
Scroll down to plugins and click Add Plugin.
Find and select the Response Transformer Advanced plugin.

Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
If the option is available, select Scoped.
Add the Route ID if it is not already prefilled.
Click Create.

Enabling the plugin on a consumer

Admin API

Kubernetes

Declarative (YAML)

Kong Manager

For example, configure this plugin on a consumer with:

$ curl -X POST http://{HOST}:8001/consumers/{CONSUMER}/plugins \
    --data "name=response-transformer-advanced"  \
    --data "config.remove.headers=x-toremove" \
    --data "config.remove.headers=x-another-one:application/json" \
    --data "config.remove.headers=x-list-of-values:v1,v2,v3" \
    --data "config.remove.headers=Set-Cookie:/JSESSIONID=.*/" \
    --data "config.remove.headers=x-another-regex://status/$/" \
    --data "config.remove.headers=x-one-more-regex:/^/begin//" \
    --data "config.remove.json=json-key-toremove" \
    --data "config.remove.json=another-json-key" \
    --data "config.add.headers=x-new-header:value" \
    --data "config.add.headers=x-another-header:something" \
    --data "config.add.json=new-json-key:some_value" \
    --data "config.add.json=another-json-key:some_value" \
    --data "config.add.json_types=new-json-key:string" \
    --data "config.add.json_types=another-json-key:boolean" \
    --data "config.add.json_types=another-json-key:number" \
    --data "config.append.headers=x-existing-header:some_value" \
    --data "config.append.headers=x-another-header:some_value"

CONSUMER is the id or username of the consumer that this plugin configuration will target.

You can combine consumer.id, service.id, or route.id in the same request, to further narrow the scope of the plugin.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <response-transformer-advanced-example>
config: 
  remove:
    headers:
    - x-toremove
    - x-another-one:application/json
    - x-list-of-values:v1,v2,v3
    - Set-Cookie:/JSESSIONID=.*/
    - x-another-regex://status/$/
    - x-one-more-regex:/^/begin//
  remove:
    json:
    - json-key-toremove
    - another-json-key
  add:
    headers:
    - x-new-header:value
    - x-another-header:something
  add:
    json:
    - new-json-key:some_value
    - another-json-key:some_value
  add:
    json_types:
    - new-json-key:string
    - another-json-key:boolean
    - another-json-key:number
  append:
    headers:
    - x-existing-header:some_value
    - x-another-header:some_value
plugin: response-transformer-advanced

Then, apply it to a consumer by annotating the KongConsumer resource as follows:

apiVersion: configuration.konghq.com/v1
kind: KongConsumer
metadata:
  name: {CONSUMER}
  annotations:
    konghq.com/plugins: <response-transformer-advanced-example>
    kubernetes.io/ingress.class: kong

CONSUMER is the id or username of the consumer that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any Service, Consumer, or Route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

For example, configure this plugin on a consumer by adding this section to your declarative configuration file:

plugins:
- name: response-transformer-advanced
  consumer: {CONSUMER}
  config: 
    remove:
      headers:
      - x-toremove
      - x-another-one:application/json
      - x-list-of-values:v1,v2,v3
      - Set-Cookie:/JSESSIONID=.*/
      - x-another-regex://status/$/
      - x-one-more-regex:/^/begin//
    remove:
      json:
      - json-key-toremove
      - another-json-key
    add:
      headers:
      - x-new-header:value
      - x-another-header:something
    add:
      json:
      - new-json-key:some_value
      - another-json-key:some_value
    add:
      json_types:
      - new-json-key:string
      - another-json-key:boolean
      - another-json-key:number
    append:
      headers:
      - x-existing-header:some_value
      - x-another-header:some_value

CONSUMER is the id or username of the consumer that this plugin configuration will target.

Configure this plugin on a consumer:

In Kong Manager, select the workspace.
From the Dashboard, scroll down to Consumers and click View for the consumer row.
Select the Plugins tab.
Click Add Plugin.
Find and select the Response Transformer Advanced plugin.

Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
If the option is available, select Global.
Click Create.

Enable the plugin globally

A plugin which is not associated to any service, route, or consumer is considered global, and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

Admin API

Kubernetes

Declarative (YAML)

Kong Manager

For example, configure this plugin globally with:

$ curl -X POST http://{HOST}:8001/plugins/ \
    --data "name=response-transformer-advanced"  \
    --data "config.remove.headers=x-toremove" \
    --data "config.remove.headers=x-another-one:application/json" \
    --data "config.remove.headers=x-list-of-values:v1,v2,v3" \
    --data "config.remove.headers=Set-Cookie:/JSESSIONID=.*/" \
    --data "config.remove.headers=x-another-regex://status/$/" \
    --data "config.remove.headers=x-one-more-regex:/^/begin//" \
    --data "config.remove.json=json-key-toremove" \
    --data "config.remove.json=another-json-key" \
    --data "config.add.headers=x-new-header:value" \
    --data "config.add.headers=x-another-header:something" \
    --data "config.add.json=new-json-key:some_value" \
    --data "config.add.json=another-json-key:some_value" \
    --data "config.add.json_types=new-json-key:string" \
    --data "config.add.json_types=another-json-key:boolean" \
    --data "config.add.json_types=another-json-key:number" \
    --data "config.append.headers=x-existing-header:some_value" \
    --data "config.append.headers=x-another-header:some_value"

Create a KongClusterPlugin resource and label it as global:

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: <global-response-transformer-advanced>
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: \"true\"
config: 
  remove:
    headers:
    - x-toremove
    - x-another-one:application/json
    - x-list-of-values:v1,v2,v3
    - Set-Cookie:/JSESSIONID=.*/
    - x-another-regex://status/$/
    - x-one-more-regex:/^/begin//
  remove:
    json:
    - json-key-toremove
    - another-json-key
  add:
    headers:
    - x-new-header:value
    - x-another-header:something
  add:
    json:
    - new-json-key:some_value
    - another-json-key:some_value
  add:
    json_types:
    - new-json-key:string
    - another-json-key:boolean
    - another-json-key:number
  append:
    headers:
    - x-existing-header:some_value
    - x-another-header:some_value
plugin: response-transformer-advanced

For example, configure this plugin using the plugins: entry in the declarative configuration file:

plugins:
- name: response-transformer-advanced
  config: 
    remove:
      headers:
      - x-toremove
      - x-another-one:application/json
      - x-list-of-values:v1,v2,v3
      - Set-Cookie:/JSESSIONID=.*/
      - x-another-regex://status/$/
      - x-one-more-regex:/^/begin//
    remove:
      json:
      - json-key-toremove
      - another-json-key
    add:
      headers:
      - x-new-header:value
      - x-another-header:something
    add:
      json:
      - new-json-key:some_value
      - another-json-key:some_value
    add:
      json_types:
      - new-json-key:string
      - another-json-key:boolean
      - another-json-key:number
    append:
      headers:
      - x-existing-header:some_value
      - x-another-header:some_value

Configure this plugin globally:

In Kong Manager, select the workspace.
From the Dashboard, select Plugins in the left navigation.
Click New Plugin.
Find and select the Response Transformer Advanced plugin.

Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
If the option is available, set the plugin scope to Global.
Click Create.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Form Parameter	Description
`name` required Type: string	The name of the plugin, in this case `response-transformer-advanced`.
`service.id` Type: string	The ID of the Service the plugin targets.
`route.id` Type: string	The ID of the Route the plugin targets.
`consumer.id` Type: string	The ID of the Consumer the plugin targets.
`enabled` required Type: boolean Default value: `true`	Whether this plugin will be applied.
`config.remove.headers` optional Type: array of string elements	List of `headername[:value]`. If only `headername` is given, unset the header field with the given `headername`. If `headername:value` is given, unset the header field `headername` when it has a specific `value`. If `value` starts and ends with a `/` (slash character), then it is considered to be a regular expression. Note that in accordance with RFC 7230 multiple header values with the same header name are allowed if the entire field value for that header field is defined as a comma-separated list or the header field is a `Set-Cookie` header field.
`config.remove.json` optional Type: array of string elements	List of property names. Remove the property from the JSON body if it is present.
`config.remove.if_status` optional Type: array of string elements	List of response status codes or status code ranges to which the transformation will apply. Empty means all response codes.
`config.rename.headers` optional Type: array of string elements	List of `headername1:headername2` pairs. If a header with `headername1` exists and `headername2` is valid, rename header to `headername2`.
`config.rename.if_status` optional Type: array of string elements	List of response status codes or status code ranges to which the transformation will apply. Empty means all response codes.
`config.replace.headers` optional Type: array of string elements	List of `headername:value` pairs. If and only if the header is already set, replace its old value with the new one. Ignored if the header is not already set.
`config.replace.json` optional Type: array of string elements	List of property `name:value` pairs. If and only if the parameter is already present, replace its old value with the new one. Ignored if the parameter is not already present.
`config.replace.json_types` optional Type: array of string, boolean, or number elements	List of JSON type names. Specify the types of the JSON values returned when replacing JSON properties.
`config.replace.body` optional Type: string	String with which to replace the entire response body.
`config.replace.if_status` optional Type: array of string elements	List of response status codes or status code ranges to which the transformation will apply. Empty means all response codes.
`config.add.headers` optional Type: array of string elements	List of `headername:value` pairs. If and only if the header is not already set, set a new header with the given value. Ignored if the header is already set.
`config.add.json` optional Type: array of string elements	List of `name:value` pairs. If and only if the property is not present, add a new property with the given value to the JSON body. Ignored if the property is already present.
`config.add.json_types` optional Type: array of string, boolean, or number elements	List of JSON type names. Specify the types of the JSON values returned when adding a new JSON property.
`config.add.if_status` optional Type: array of string elements	List of response status codes or status code ranges to which the transformation will apply. Empty means all response codes.
`config.append.headers` optional Type: array of string elements	List of `headername:value` pairs. If the header is not set, set it with the given value. If it is already set, a new header with the same name and the new value will be set.
`config.append.json` optional Type: array of string elements	List of `name:value` pairs. If the property is not present in the JSON body, add it with the given value. If it is already present, the two values (old and new) will be aggregated in an array.
`config.append.json_types` optional Type: array of string, boolean, or number elements	List of JSON type names. Specify the types of the JSON values returned when appending JSON properties.
`config.append.if_status` optional	List of response status codes or status code ranges to which the transformation will apply. Empty means all response codes.
`config.allow.json` optional Type: array of string elements	Set of parameter names. Only allowed parameters are present in the JSON response body.
`config.transform.functions` optional Type: array of function elements	Set of Lua functions to perform arbitrary transforms in a response JSON body.
`config.transform.if_status` optional Type: array of string elements	List of response status codes or ranges to which the arbitrary transformation applies. Leaving empty implies that the transformations apply to all response codes.
`config.transform.json` optional Type: array of string elements	Apply Lua functions to a particular list of JSON property `name` or `name:value` pairs.
`config.dots_in_keys` optional Type: boolean Default value: `true`	Whether dots (for example, `customers.info.phone`) should be treated as part of a property name or used to descend into nested JSON objects. See Arrays and nested objects.

Note: If the value contains a , (comma), then the comma-separated format for lists cannot be used. The 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 is 1).
top.sub: Navigates to the sub property of the top 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	h1: v1 h2: 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	h1: v1 h2: 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	h1: v1 h2: 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	h1: v2 h2: v1
h3: v1	h1: v1 h2: v1 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	h1: v1 h1: v2 h2: 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 a number (instead of the implicitly inferred type string) 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"

About this Plugin
Plugin Version	2.3.x
Made by	Kong Inc.
Categories	Transformations
DB-less compatible?	Yes
Konnect Cloud compatible?	Yes
Version Compatibility
Kong Gateway 2.8.x 2.7.x 2.6.x 2.5.x 2.4.x 2.3.x 2.2.x 2.1.x 1.5.x 1.3-x 0.36-x