Assign attributes policy

Phases

V3 engine

onRequest	onResponse	onRequestContent	onResponseContent
X	X	X	X

V4 engine

onRequest	onResponse	onMessageRequest	onMessageResponse
X	X	X	X

Description

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

When you are using this policy on the message request or response, the attribute will be available in the message attribute list and not on the context one.

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).

Compatibility with APIM

Plugin version	APIM version
Up to 1.x	All
From 2.x	4.0+

Configuration

You can configure the policy with the following options:

Table 1. Configuration

Property	Required	Description	Type	Default
scope	only for v3 engine	The execution scope (request or response)	string	REQUEST
attributes	X	List of attributes	See Attribute

Table 2. Attribute

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

Examples

Request header

Let’s say we want to inject request attributes into the context attributes.

"assign-attributes": {
    "attributes": [
        {
            "name": "initialContentTypeHeader,
            "value": "{#request.headers['Content-Type']}"
        },
        {
            "name": "initialFooParamHeader,
            "value": "{#request.params['foo']}"
        }
    ]
}

To extract the request attributes you can use the following syntax:

Get the content-type header:

{#context.attributes['initialContentTypeHeader']}

Get the foo query param:

{#context.attributes['initialFooParamHeader']}

Request objects

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

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

To extract the request attributes you can use the following syntax:

Get the content-type header:

{#context.attributes['initialRequest'].headers['content-type']}

Get the foo query param:

{#context.attributes['initialRequest'].params['foo']}

Message

You can use for example the content of a message:

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

Errors

HTTP status code

Code	Message
500	An error occurred while setting request attributes in the execution context