HTTP Callout Policy

The callout-http policy invokes an HTTP(S) URL and places a subset or all of the content in one or more variables of the request execution context.

This can be useful if you need some data from an external service and want to inject it during request processing.

This policy can be attached to the following phases:

• onRequest / onRequestContent: Executed before the request reaches your backend service.

• onResponse / onResponseContent: Executed after the backend service responds, but before the client receives it.

By default, the callout result is stored in a temporary calloutResponse variable available only while the policy is executing. To use this data in subsequent policies or send it to your backend, you must define a custom variable in the variables configuration property.

Timing

On Request	On Response
X	X

Configuration

Property	Required	Description	Type	Default
method	yes	HTTP Method used to invoke URL. Options are: CONNECT, DELETE, GET, HEAD, OPTIONS, PATCH, POST, PUT, TRACE	HTTP method	GET
url	yes	URL invoked by the HTTP client (supports EL).	URL
Cache Enabled	no	Enables or disables caching for this policy. Set to true to enable the caching mechanism.	Boolean	false
Cache Refresh Time	no	Specifies the cache duration in seconds. Use this to set a static Time-to-Live (TTL) for cached data. The default value is 3600 seconds (1hour).	Integer	3600
Cache Key	yes	Defines the unique identifier for a cached entry. Construct the key using specific request attributes—such as path, query parameters, or headers—to ensure that each request has a unique cache entry. Warning: When updating existing or configuring new HTTP Callout policies with caching disabled, you must still populate the Cache Key field with a placeholder string (e.g., not-applicable or temp) to satisfy the mandatory field requirement. Please note that this is a temporary requirement and will be resolved in the upcoming release.	String	""
headers	no	List of HTTP headers used to invoke the URL (supports EL).	HTTP headers
body	no	The body content send when calling the URL (supports EL).	string
fireAndForget	no	Make the HTTP call without expecting any response. When activating this mode, context variables and exit on error are ignored.	boolean	false
variables	no	The variables to set in the execution context when retrieving content of HTTP call (supports EL). Use the variables to persist data for use in later policies.	List of variables
exitOnError	no	Terminate the request if the error condition is true.	boolean	false
errorCondition	no	The condition that will be verified to end the request (supports EL).	string	{#calloutResponse.status >= 400 and #calloutResponse.status <= 599}
errorStatusCode	no	HTTP Status Code sent to the consumer if the condition is true.	int	500
errorContent	no	The body response of the error if the condition is true (supports EL).	string

Example

In this example, a value is extracted from the calloutResponse and stored in a variable named my-server. You can then reference this in a later policy (such as Transform Headers) using the syntax {#context.attributes['my-server']}.

{
  "policy-http-callout": {
    "method": "GET",
    "url": "https://api.boomi.io/echo",
    "cacheEnabled": false,
    "cacheRefreshTime": 3600,
    "cacheKey": "",
    "headers": [
      {
        "name": "Authorization",
        "value": "{#request.headers['Authorization']}"
      }
    ],
    "body": "{}",
    "fireAndForget": false,
    "variables": [
      {
        "name": "my-server",
        "value": "{#jsonPath(#calloutResponse.content, '$.msg')}"
      }
    ],
    "exitOnError": false,
    "errorCondition": "{#calloutResponse.status>= 400 and #calloutResponse.status<= 599}",
    "errorStatusCode": 400,
    "errorContent": "Getting error while invoking the url",
    "scope": "REQUEST"
  }
}

Override errors

You can override the default response provided by the policy with the response templates feature. These templates must be defined at the API level with the APIM Console Proxy > Response Templates function. Use the following keys to override the default behavior:

• CALLOUT_EXIT_ON_ERROR: Message sent when the errorCondition is met.

• CALLOUT_HTTP_ERROR: Message sent when the Gateway fails to connect to the destination URL.