assign-attributes.md

description
This page provides the technical details of the Assign Attributes policy

Assign Attributes

Overview

You can use the assign-attributes policy to set variables such as request attributes and other execution context attributes.

You can use it to retrieve initial request attributes after Transform headers or Transform query parameters policies and reuse them in other policies (Dynamic routing, for example).

Functional and implementation information for the assign-attributes 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" %} To inject an attribute that will dynamically determine if the content is in JSON format:

"assign-attributes": {
    "attributes": [
        {
            "name": "isJson,
            "value": "'application/json'.equals(#request.headers['Content-Type'])"
        }
    ]
}

To extract the request attribute and get the format of the content you can use the following syntax:

{#context.attributes['isJson']}

Request objects

You can also be more general and inject complex objects into the context attributes:

"assign-attributes": {
    "attributes": [
        {
            "name": "initialRequest,
            "value": "{#request}"
        }
    ]
}

To extract request attributes and get the Content-Type header you can use the following syntax:

{#context.attributes['initialRequest'].headers['Content-Type']}

{% endtab %}

{% tab title="Message API example" %} To inject an attribute that will dynamically determine if the content is in JSON format:

"assign-attributes": {
    "attributes": [
        {
            "name": "isJson,
            "value": "'application/json'.equals(#message.headers['Content-Type'])"
        }
    ]
}

To extract the message attribute and get the format of the content you can use the following syntax:

{#message.attributes['isJson']}

Message objects

You can also be more general and inject complex objects into the message attributes:

"assign-attributes": {
    "attributes": [
        {
            "name": "initialMessage,
            "value": "{#message}"
        }
    ]
}

To extract message attributes and get the Content-Type header you can use the following syntax:

{#message.attributes['initialMessage'].headers['Content-Type']}

To assign an attribute to the content of a message:

"assign-attributes": {
    "attributes": [
        {
            "name": "messageContent,
            "value": "{#message.content}"
        }
    ]
}

{% endtab %} {% endtabs %}

Configuration

Phases

The phases checked below are supported by the assign-attributes policy:

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

Options

You can configure the assign-attributes policy with the following options:

Property	Required	Description	Type	Default
scope	only for v4 proxy APIs	The execution scope (request or response)	string	REQUEST
attributes	X	List of attributes	See table below

Attributes

You can configure the assign-attributes policy with the following attributes:

Property	Required	Description	Type	Default
name	X	Attribute name	string
value	X	Attribute value (can be EL)	string

Compatibility matrix

The following is the compatibility matrix for APIM and the assign-attributes policy:

Plugin Version	Supported APIM versions
Up to 1.x	All
From 2.x	4.0+

Errors

Phase	HTTP status code	Error template key
onRequest	500	An error occurred while setting request attributes in the execution context
onResponse	500	An error occurred while setting request attributes in the execution context
onRequestContent	500	An error occurred while setting request attributes in the execution context
onResponseContent	500	An error occurred while setting request attributes in the execution context
onMessageRequest	500	An error occurred while setting request attributes in the execution context
onMessageResponse	500	An error occurred while setting request attributes in the execution context

Changelogs

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