body-transformer - Apisix

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Description

The body-transformer Plugin performs template-based transformations to transform the request and/or response bodies from one format to another, for example, from JSON to JSON, JSON to HTML, or XML to YAML.

Attributes

Name	Type	Required	Default	Valid values	Description
`request`	object	False			Request body transformation configuration.
`request.input_format`	string	False		[`xml`,`json`,`encoded`,`args`,`plain`,`multipart`]	Request body original media type. If unspecified, the value would be determined by the `Content-Type` header to apply the corresponding decoder. The `xml` option corresponds to `text/xml` media type. The `json` option corresponds to `application/json` media type. The `encoded` option corresponds to `application/x-www-form-urlencoded` media type. The `args` option corresponds to GET requests. The `plain` option corresponds to `text/plain` media type. The `multipart` option corresponds to `multipart/related` media type. If the media type is neither type, the value would be left unset and the transformation template will be directly applied.
`request.template`	string	True			Request body transformation template. The template uses lua-resty-template syntax. See the template syntax for more details. You can also use auxiliary functions `_escape_json()` and `_escape_xml()` to escape special characters such as double quotes, `_body` to access request body, and `_ctx` to access context variables.
`request.template_is_base64`	boolean	False	false		Set to true if the template is base64 encoded.
`response`	object	False			Response body transformation configuration.
`response.input_format`	string	False		[`xml`,`json`,`encoded`,`args`,`plain`,`multipart`]	Response body original media type. If unspecified, the decoder is determined by the `Content-Type` header where applicable: `xml` for `text/xml`, `json` for `application/json`, `encoded` for `application/x-www-form-urlencoded`, and `multipart` for any `multipart/*` content type. The `args` option reads URI query args from the request rather than decoding the response body. The `plain` option must be set explicitly and is not auto-detected from `Content-Type: text/plain`. If the media type is none of the supported types above, the value will be left unset and the transformation template will be directly applied.
`response.template`	string	True			Response body transformation template.
`response.template_is_base64`	boolean	False	false		Set to true if the template is base64 encoded.

Examples

The examples below demonstrate how you can configure body-transformer for different scenarios.

:::note

You can fetch the admin_key from config.yaml and save to an environment variable with the following command:

bash

admin_key=$(yq '.deployment.admin.admin_key[0].key' conf/config.yaml | sed 's/"//g')

:::

The transformation template uses lua-resty-template syntax. See the template syntax to learn more.

You can also use auxiliary functions _escape_json() and _escape_xml() to escape special characters such as double quotes, _body to access request body, and _ctx to access context variables.

In all cases, you should ensure that the transformation template is a valid JSON string.

Transform between JSON and XML SOAP

The following example demonstrates how to transform the request body from JSON to XML and the response body from XML to JSON when working with a SOAP Upstream service.

Start the sample SOAP service:

shell

cd /tmp
git clone https://github.com/spring-guides/gs-soap-service.git
cd gs-soap-service/complete
./mvnw spring-boot:run

Create the request and response transformation templates:

shell

req_template=$(cat <<EOF | awk '{gsub(/"/,"\\\"");};1' | awk '{$1=$1};1' | tr -d '\r\n'
<?xml version="1.0"?>
<soap-env:Envelope xmlns:soap-env="http://schemas.xmlsoap.org/soap/envelope/">
 <soap-env:Body>
  <ns0:getCountryRequest xmlns:ns0="http://spring.io/guides/gs-producing-web-service">
   <ns0:name>{{_escape_xml(name)}}</ns0:name>
  </ns0:getCountryRequest>
 </soap-env:Body>
</soap-env:Envelope>
EOF
)

rsp_template=$(cat <<EOF | awk '{gsub(/"/,"\\\"");};1' | awk '{$1=$1};1' | tr -d '\r\n'
{% if Envelope.Body.Fault == nil then %}
{
  "status":"{{_ctx.var.status}}",
  "currency":"{{Envelope.Body.getCountryResponse.country.currency}}",
  "population":{{Envelope.Body.getCountryResponse.country.population}},
  "capital":"{{Envelope.Body.getCountryResponse.country.capital}}",
  "name":"{{Envelope.Body.getCountryResponse.country.name}}"
}
{% else %}
{
  "message":{*_escape_json(Envelope.Body.Fault.faultstring[1])*},
  "code":"{{Envelope.Body.Fault.faultcode}}"
  {% if Envelope.Body.Fault.faultactor ~= nil then %}
  , "actor":"{{Envelope.Body.Fault.faultactor}}"
  {% end %}
}
{% end %}
EOF
)

awk and tr are used above to manipulate the template such that the template would be a valid JSON string.

Create a Route with body-transformer using the templates created previously. In the Plugin, set the request input format as JSON, the response input format as XML, and the Content-Type header to text/xml for the Upstream service to respond properly:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "methods": ["POST"],
    "uri": "/ws",
    "plugins": {
      "body-transformer": {
        "request": {
          "template": "'"$req_template"'",
          "input_format": "json"
        },
        "response": {
          "template": "'"$rsp_template"'",
          "input_format": "xml"
        }
      },
      "proxy-rewrite": {
        "headers": {
          "set": {
            "Content-Type": "text/xml"
          }
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "localhost:8080": 1
      }
    }
  }'

:::tip

If it is cumbersome to adjust complex text files to be valid transformation templates, you can use the base64 utility to encode the files, such as the following:

json

"body-transformer": {
  "request": {
    "template": "'"$(base64 -w0 /path/to/request_template_file)"'"
  },
  "response": {
    "template": "'"$(base64 -w0 /path/to/response_template_file)"'"
  }
}

:::

Send a request with a valid JSON body:

shell

curl "http://127.0.0.1:9080/ws" -X POST -d '{"name": "Spain"}'

The JSON body sent in the request will be transformed into XML before being forwarded to the Upstream SOAP service, and the response body will be transformed back from XML to JSON.

You should see a response similar to the following:

json

{
  "status": "200",
  "currency": "EUR",
  "population": 46704314,
  "capital": "Madrid",
  "name": "Spain"
}

Modify Request Body

The following example demonstrates how to dynamically modify the request body.

Create a Route with body-transformer, in which the template appends the word world to the name and adds 10 to the age to set them as values to foo and bar respectively:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "template": "{\"foo\":\"{{name .. \" world\"}}\",\"bar\":{{age+10}}}"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a request to the Route:

shell

curl "http://127.0.0.1:9080/anything" -X POST \
  -H "Content-Type: application/json" \
  -d '{"name":"hello","age":20}' \
  -i

You should see a response of the following:

json

{
  "args": {},
  "data": "{\"foo\":\"hello world\",\"bar\":30}",
  ...
  "json": {
    "bar": 30,
    "foo": "hello world"
  },
  "method": "POST",
  ...
}

Generate Request Body Using Variables

The following example demonstrates how to generate request body dynamically using the ctx context variables.

Create a Route with body-transformer, in which the template accesses the request argument using the Nginx variable arg_name:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "template": "{\"foo\":\"{{_ctx.var.arg_name .. \" world\"}}\"}"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a request to the Route with name argument:

shell

curl -i "http://127.0.0.1:9080/anything?name=hello"

You should see a response like this:

json

{
  "args": {
    "name": "hello"
  },
  ...,
  "json": {
    "foo": "hello world"
  },
...
}

Transform Body from YAML to JSON

The following example demonstrates how to transform request body from YAML to JSON.

Create the request transformation template:

shell

req_template=$(cat <<EOF | awk '{gsub(/"/,"\\\"");};1'
{%
    local yaml = require("tinyyaml")
    local body = yaml.parse(_body)
%}
{"foobar":"{{body.foobar.foo .. " " .. body.foobar.bar}}"}
EOF
)

Create a Route with body-transformer that uses the template:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "template": "'"$req_template"'"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a request to the Route with a YAML body:

shell

body='
foobar:
  foo: hello
  bar: world'

curl "http://127.0.0.1:9080/anything" -X POST \
  -d "$body" \
  -H "Content-Type: text/yaml" \
  -i

You should see a response similar to the following, which verifies that the YAML body was appropriately transformed to JSON:

json

{
  "args": {},
  "data": "{\"foobar\":\"hello world\"}",
  ...
  "json": {
    "foobar": "hello world"
  },
...
}

Transform Form URL Encoded Body to JSON

The following example demonstrates how to transform form-urlencoded body to JSON.

Create a Route with body-transformer which sets the input_format to encoded and configures a template that appends string world to the name input, add 10 to the age input:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "input_format": "encoded",
          "template": "{\"foo\":\"{{name .. \" world\"}}\",\"bar\":{{age+10}}}"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a POST request to the Route with an encoded body:

shell

curl "http://127.0.0.1:9080/anything" -X POST \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d 'name=hello&age=20'

You should see a response similar to the following:

json

{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "{\"foo\":\"hello world\",\"bar\":30}": ""
  },
  "headers": {
    ...
  },
  ...
}

Transform GET Request Query Parameter to Body

The following example demonstrates how to transform a GET request query parameter to request body. Note that this does not transform the HTTP method. To transform the method, see proxy-rewrite.

Create a Route with body-transformer, which sets the input_format to args and configures a template that adds a message to the request:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "input_format": "args",
          "template": "{\"message\": \"hello {{name}}\"}"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a GET request to the Route:

shell

curl "http://127.0.0.1:9080/anything?name=john"

You should see a response similar to the following:

json

{
  "args": {},
  "data": "{\"message\": \"hello john\"}",
  "files": {},
  "form": {},
  "headers": {
    ...
  },
  "json": {
    "message": "hello john"
  },
  "method": "GET",
  ...
}

Transform Plain Media Type

The following example demonstrates how to transform requests with plain media type.

Create a Route with body-transformer, which sets the input_format to plain and configures a template to remove not and a subsequent space from the body string:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "input_format": "plain",
          "template": "{\"message\": \"{* string.gsub(_body, \"not \", \"\") *}\"}"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a POST request to the Route:

shell

curl "http://127.0.0.1:9080/anything" -X POST \
  -d 'not actually json' \
  -i

You should see a response similar to the following:

json

{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "{\"message\": \"actually json\"}": ""
  },
  "headers": {
    ...
  },
  ...
}

Transform Multipart Media Type

The following example demonstrates how to transform requests with multipart media type.

Create a request transformation template which adds a status to the body based on the age provided in the request body:

shell

req_template=$(cat <<EOF | awk '{gsub(/"/,"\\\"");};1'
{%
  local core = require 'apisix.core'
  local cjson = require 'cjson'

  if tonumber(context.age) > 18 then
      context._multipart:set_simple("status", "adult")
  else
      context._multipart:set_simple("status", "minor")
  end

  local body = context._multipart:tostring()
%}{* body *}
EOF
)

Create a Route with body-transformer, which sets the input_format to multipart and uses the previously created request template for transformation:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/anything",
    "plugins": {
      "body-transformer": {
        "request": {
          "input_format": "multipart",
          "template": "'"$req_template"'"
        }
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

Send a multipart POST request to the Route:

shell

curl -X POST \
  -F "name=john" \
  -F "age=10" \
  "http://127.0.0.1:9080/anything"

You should see a response similar to the following:

json

{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "age": "10",
    "name": "john",
    "status": "minor"
  },
  "headers": {
    "Accept": "*/*",
    "Content-Length": "361",
    "Content-Type": "multipart/form-data; boundary=------------------------qtPjk4c8ZjmGOXNKzhqnOP",
    ...
  },
  ...
}

Transform Response Body Based on Consumer Identity

The following example demonstrates how to customize response body transformations based on different Consumer identities. The example shows how to return different response formats to different Consumers while filtering sensitive fields and renaming properties.

Create the response transformation template that applies different transformations based on the Consumer identity:

shell

rsp_template=$(cat <<EOF | awk '{gsub(/"/,"\\\"");};1' | awk '{$1=$1};1' | tr -d '\r\n'
{% local consumer_name = _ctx.consumer and _ctx.consumer.username or "" %}
{% if consumer_name == "consumer-a" then %}
{
  "user_id": {* user_id *},
  "display_name": {* _escape_json(username) *},
  "email": {* _escape_json(email) *}
}
{% elseif consumer_name == "consumer-b" then %}
{
  "user_id": {* user_id *},
  "email": {* _escape_json(email) *},
  "balance": {* balance *}
}
{% else %}
{* _body *}
{% end %}
EOF
)

Create three Consumers with key-auth configured:

shell

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "consumer-a",
    "plugins": {
      "key-auth": {
        "key": "consumer-a"
      }
    }
  }'

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "consumer-b",
    "plugins": {
      "key-auth": {
        "key": "consumer-b"
      }
    }
  }'

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "consumer-c",
    "plugins": {
      "key-auth": {
        "key": "consumer-c"
      }
    }
  }'

Create a Route with body-transformer, key-auth, and mocking Plugins:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/mock",
    "plugins": {
      "key-auth": {},
      "mocking": {
        "response_example": "{\"user_id\":1001,\"username\":\"john_doe\",\"email\":\"[email protected]\",\"phone\":\"+1-555-0123\",\"balance\":1250.50}"
      },
      "body-transformer": {
        "response": {
          "input_format": "json",
          "template": "'"$rsp_template"'"
        }
      }
    }
  }'

Send requests with different apikey headers to verify the response transformations.

Send a request as consumer-a:

shell

curl "http://127.0.0.1:9080/mock" -H "apikey: consumer-a"

You should see a response similar to the following, which demonstrates these transformations:

The username field has been renamed to display_name
The sensitive phone and balance fields have been filtered out

json

{
  "user_id": 1001,
  "display_name": "john_doe",
  "email": "[email protected]"
}

Send a request as consumer-b:

shell

curl "http://127.0.0.1:9080/mock" -H "apikey: consumer-b"

You should see a response similar to the following, which demonstrates these transformations:

The username and phone fields have been filtered out
The balance field has been preserved

json

{
  "user_id": 1001,
  "email": "[email protected]",
  "balance": 1250.50
}

Send a request as consumer-c:

shell

curl "http://127.0.0.1:9080/mock" -H "apikey: consumer-c"

You should see a response similar to the following, which shows that the original response is returned unchanged:

json

{
  "user_id": 1001,
  "username": "john_doe",
  "email": "[email protected]",
  "phone": "+1-555-0123",
  "balance": 1250.50
}

Transform Nested Response Body Based on Consumer Identity

The following example demonstrates how to customize response body transformations based on different Consumer identities. The example shows how to extract nested fields, reorganize data structures, and flatten nested objects while providing different response formats to different Consumers based on their identity.

Create the response transformation template that extracts and reorganizes nested JSON fields based on the Consumer identity:

shell

rsp_template=$(cat <<EOF | awk '{gsub(/"/,"\\\"");};1' | awk '{$1=$1};1' | tr -d '\r\n'
{% local consumer_name = _ctx.consumer and _ctx.consumer.username or "" %}
{% if consumer_name == "consumer-a" then %}
{
  "user_id": {* id *},
  "user_name": {* _escape_json(name) *},
  "email": {* _escape_json(profile.email) *},
  "location": {
    "city": {* _escape_json(profile.address.city) *},
    "country": {* _escape_json(profile.address.country) *}
  },
  "created_at": {* _escape_json(metadata.created_at) *}
}
{% elseif consumer_name == "consumer-b" then %}
{
  "id": {* id *},
  "name": {* _escape_json(name) *},
  "status": {* _escape_json(status) *},
  "profile": {
    "email": {* _escape_json(profile.email) *},
    "address": {
      "city": {* _escape_json(profile.address.city) *}
    }
  }
}
{% else %}
{* _body *}
{% end %}
EOF
)

Create Consumers with key-auth configured:

shell

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "consumer-a",
    "plugins": {
      "key-auth": {
        "key": "consumer-a"
      }
    }
  }'

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "consumer-b",
    "plugins": {
      "key-auth": {
        "key": "consumer-b"
      }
    }
  }'

curl "http://127.0.0.1:9180/apisix/admin/consumers" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "username": "consumer-c",
    "plugins": {
      "key-auth": {
        "key": "consumer-c"
      }
    }
  }'

Create a Route with body-transformer, key-auth, and mocking Plugins using the nested structure template:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "body-transformer-route",
    "uri": "/mock",
    "plugins": {
      "key-auth": {},
      "mocking": {
        "response_example": "{\"id\":123,\"name\":\"John Doe\",\"status\":\"active\",\"profile\":{\"email\":\"[email protected]\",\"address\":{\"city\":\"New York\",\"country\":\"USA\"}},\"metadata\":{\"created_at\":\"2024-01-01\",\"tags\":[\"vip\",\"premium\"]}}"
      },
      "body-transformer": {
        "response": {
          "input_format": "json",
          "template": "'"$rsp_template"'"
        }
      }
    }
  }'

Send a request as consumer-a to verify the nested structure transformation:

shell

curl "http://127.0.0.1:9080/mock" -H "apikey: consumer-a"

You should see a response similar to the following, which demonstrates these nested field transformations:

profile.email has been extracted to top-level email
profile.address.city and profile.address.country have been combined into a new location object
metadata.created_at has been extracted to top-level created_at

json

{
  "user_id": 123,
  "user_name": "John Doe",
  "email": "[email protected]",
  "location": {
    "city": "New York",
    "country": "USA"
  },
  "created_at": "2024-01-01"
}

Send a request as consumer-b to verify the nested structure transformation:

shell

curl "http://127.0.0.1:9080/mock" -H "apikey: consumer-b"

You should see a response similar to the following, which demonstrates these transformations:

The original profile object structure has been preserved
profile.address.country and metadata fields have been filtered out

json

{
  "id": 123,
  "name": "John Doe",
  "status": "active",
  "profile": {
    "email": "[email protected]",
    "address": {
      "city": "New York"
    }
  }
}

Send a request as consumer-c to verify the nested structure transformation:

shell

curl "http://127.0.0.1:9080/mock" -H "apikey: consumer-c"

You should see a response similar to the following, which shows that the original nested response is returned unchanged:

json

{
  "id": 123,
  "name": "John Doe",
  "status": "active",
  "profile": {
    "email": "[email protected]",
    "address": {
      "city": "New York",
      "country": "USA"
    }
  },
  "metadata": {
    "created_at": "2024-01-01",
    "tags": ["vip", "premium"]
  }
}