Intervening a running process at a certain position and redirecting the process flow in order to include project-specific processing steps.

Introduction

The interceptors allow for project-specific extensions of the yuuvis® Momentum standard process flows. The running process flow can be redirected by a condition set on the processed object that has to be specified in the interceptor definition. Whenever the process flow meets the condition, the project-specific process extension is included for the currently processed object at this position of the process flow. Thus, the alternative process can entirely replace the standard one from this position on or resume the standard process at a specified position.

Interceptor Configuration

The condition for the intervention of the process flow is defined in the interceptor configuration file \system\interceptorConfiguration.json.

Parameters

The following parameters are available for the interceptor configuration:

Parameter	Type	Required	Description
`type`	String	yes	The type of the interceptor. It defines the position in the process flow where the interceptor can step in.
`predicate`	String	yes	The condition that triggers the redirection of the process flow in order to include the project-specific process extension. The string can provide the condition either in Spring Expression Language (SpEL) or Javascript. Thus, the string always has to start with a prefix `spel:` for SpEL or `js:` for Javascript.
`url`	String	yes	HTTP address of an external endpoint defining the project-specific process extension. Dynamic components (properties of the processed object) can be included in curly brackets.
`useDiscovery`	Boolean	no	Decides whether to resolve the `url` string at the Discovery-Service or not. If not specified, a default value is set.

Interceptor Types

There are different types of interceptors available that interrupt the process flow at different positions.

Interceptor type	Evaluation target of the predicate	Interceptor input data	Description
`getContent`	API DMS object in JSON format derived from given `objectId`	`objectId`	Manipulation of the binary content of the return statement by a project-specific service
`search`	Structure of the specific class `SearchInterceptorObject`	Search query object	Manipulation of the search query parameter and the search result.
`updateDmsObject`	First API DMS object in the list in JSON format that is passed to the corresponding update endpoint	Updated metadata and metadata of current version	Manipulation of the update properties that will be applied to a DMS object.
`dms.request.objects.upsert.database-before`	All objects of the `objects` list in the `data` part of the multipart body after enrichment.	a multipart request body	The take-off point of the interceptor is after the REPOSITORY service. The initial request body is already normalized, validated and enriched with content stream properties.

Interceptor Configuration Example

The following example configures an interceptor that will be trigger by every update of a content (action code 301). At the take-off point after the REPOSITORY service, the enriched request body is passed to the external endpoint specified by url.

To activate this configuration, the REPOSITORY service needs to be restarted.

Example interceptorConfiguration.json.

{
	"interceptors": [
		{
			"type": "dms.request.objects.upsert.database-before",
			"predicate": "spel:options['action']==301",
			"url": "http://exampleinterceptorcontentupdate/api/dms/objects/upsert",
			"useDiscovery": true
		}
	]
}

Summary

This article gave an overview of the interceptors in yuuvis® Momentum. If you want to extend the functionality of your system, system hooks also might be an interesting topic for you.

Table of Contents

Introduction

Interceptor Configuration

Parameters

Interceptor Types

Interceptor Configuration Example

Summary

Read on

Interceptor Example Tutorial

System Hooks

Preprocessing Metadata using Webhooks

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