json-to-json.md

description
This page provides the technical details of the JSON to JSON policy

JSON to JSON

Overview

You can use the json-to-json policy to apply a transformation (or mapping) on the request and/or response and/or message content.

This policy is based on the JOLT library.

In APIM, you need to provide the JOLT specification in the policy configuration.

{% hint style="info" %} You can use APIM EL in the JOLT specification. {% endhint %}

At request/response level, the policy will do nothing if the processed request/response does not contain JSON. This policy checks the Content-Type header before applying any transformation.

At message level, the policy will do nothing if the processed message has no content. It means that the message will be re-emitted as is.

Functional and implementation information for the json-to-json policy is organized into the following sections:

• Examples
• Configuration
• Compatibility Matrix
• Errors
• Changelogs

Examples

{% hint style="warning" %} This policy can be applied to v2 APIs, v4 HTTP proxy APIs, and v4 message APIs. It cannot be applied to v4 TCP proxy APIs. {% endhint %}

{% tabs %} {% tab title="HTTP proxy API example" %} For this input:

{
    "_id": "57762dc6ab7d620000000001",
    "name": "name",
    "__v": 0
}

And this JOLT specification:

[
  {
    "operation": "shift",
    "spec": {
      "_id": "id",
      "*": {
        "$": "&1"
      }
    }
  },
  {
    "operation": "remove",
    "spec": {
      "__v": ""
    }
  }
]

The output is as follows:

{
    "id": "57762dc6ab7d620000000001",
    "name": "name"
}

{% endtab %}

{% tab title="Message API example" %} For this input:

{
    "_id": "57762dc6ab7d620000000001",
    "name": "name",
    "__v": 0
}

And this JOLT specification:

[
  {
    "operation": "shift",
    "spec": {
      "_id": "id",
      "*": {
        "$": "&1"
      }
    }
  },
  {
    "operation": "remove",
    "spec": {
      "__v": ""
    }
  }
]

The output is as follows:

{
    "id": "57762dc6ab7d620000000001",
    "name": "name"
}

{% endtab %} {% endtabs %}

Configuration

Sample policy configuration is shown below:

{% code title="Sample Configuration" %}

{
    "json-to-json": {
        "scope": "REQUEST",
        "specification": "[{ \"operation\": \"shift\", \"spec\": { \"_id\": \"id\", \"*\": { \"$\": \"&1\" } } }, { \"operation\": \"remove\", \"spec\": { \"__v\": \"\" } }]"
    }
}

{% endcode %}

Options

The json-to-json policy can be configured with the following options:

Property	Required	Description	Type	Default
scope	only for legacy execution engine	The execution scope (request or response)	string	REQUEST
specification	X	The JOLT specification to apply on a given content. Can contain EL.	string
overrideContentType		Override the Content-Type to application/json	string	true

Phases

The phases checked below are supported by the json-to-json policy:

v2 Phases	Compatible?	v4 Phases	Compatible?
onRequest	true	onRequest	true
onResponse	true	onResponse	true
onRequestContent	true	onMessageRequest	true
onResponseContent	true	onMessageResponse	true

Compatibility matrix

The following is the compatibility matrix for APIM and the json-to-json policy:

Plugin Version	Supported APIM versions
1.x	Up to 3.19.x
2.x	3.20.x
3.x	4.0+

Errors

Legacy execution engine:

Code	Message
500	Bad specification file or transformation cannot be executed properly

Reactive execution engine:

Code	Error template key	Description
500	INVALID_JSON_TRANSFORMATION	Unable to apply JOLT transformation to payload

Changelogs

{% @github-files/github-code-block url="https://github.com/gravitee-io/gravitee-policy-json-xml/blob/master/CHANGELOG.md" %}