body-transformer

The body-transformer plugin performs template-based transformations to transform the request and/or response bodies from one format to another.

Examples

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

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:

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:

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:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${ADMIN_API_KEY}" \
  -d '{
    "id": "body-transformer-route",
    "methods": ["POST"],
    "uri": "/ws",
    "plugins": {
      "body-transformer": {
        "request": {
          "template": "'"$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
      }
    }
  }'

❶ Set the request input format as JSON, so that the plugin will apply the JSON decoder internally.

❷ Set the response input format as XML, so that the plugin will apply the XML decoder internally.

❸ Set the Content-Type header to text/xml for the upstream service to respond properly.

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:

"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:

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:

{
  "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:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${ADMIN_API_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
      }
    }
  }'

❶ Set a template that appends "world" to the name and adds 10 to the age and set them as values to "foo" and "bar" respectively.

Send a request to the route:

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:

{
  "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:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${ADMIN_API_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
      }
    }
  }'

❶ Set a template which accesses the request argument using the NGINX variable arg_name.

Send a request to the route with name argument:

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

You should see a response like this:

{
  "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:

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:

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

Send a request to the route with a YAML body:

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:

{
  "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-transformeras such:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${ADMIN_API_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
      }
    }
  }'

❶ Set the input_format to encoded.

❷ Set a template which appends string world to the name input, add 10 to the age input, and form a new JSON object.

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

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:

{
  "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-transformeras such:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${ADMIN_API_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
      }
    }
  }'

❶ Set the input_format to args.

❷ Set a template which adds a message to the request.

Send a GET request to the route:

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

You should see a response similar to the following:

{
  "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 as such:

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${ADMIN_API_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
      }
    }
  }'

❶ Set the input_format to plain.

❷ Set a template which removes not and a subsequent space from the body string.

Send a POST request to the route:

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

You should see a response similar to the following:

{
  "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:

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 as such:

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

❶ Set the input_format to multipart.

❷ Set to the previously created request template.

Send a multipart POST request to the route:

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:

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

body-transformer

Examples​

Transform between JSON and XML SOAP​

Modify Request Body​

Generate Request Body Using Variables​

Transform Body from YAML to JSON​

Transform Form URL Encoded Body to JSON​

Transform GET Request Query Parameter to Body​

Transform Plain Media Type​

Transform Multipart Media Type​

Examples

Transform between JSON and XML SOAP

Modify Request Body

Generate Request Body Using Variables

Transform Body from YAML to JSON

Transform Form URL Encoded Body to JSON

Transform GET Request Query Parameter to Body

Transform Plain Media Type

Transform Multipart Media Type