# UpdateAttributeFromMetadata

A processor that adds or updates a FlowFile attribute based on the value of a document metadata field or document metadata field attribute.

It can be useful to extract values from the document metadata and add them to the FlowFile as FlowFile attributes so that they can be referenced using NiFi expression language and used to customize the configuration of a downstream processor.

## Properties

Name | Description
--- | ---
FlowFile_attribute_to_set | Add as many properties as you require. The name of each property you add specifies the FlowFile attribute to add or update. The value of each property must be an XPath expression, to choose the document metadata field or document metadata field attribute to use to set the value of the FlowFile attribute. If the XPath expression results in a match, the target FlowFile attribute is added (or updated if it already exists). If the XPath expression results in multiple matches, the first is used and the others are ignored. If your XPath expression matches a field that has subfields, the field values are concatenated (the structure and field names are not preserved when the FlowFile attribute is set).

## Relationships

Name | Description
--- | ---
success | FlowFiles that were processed successfully.
failure | FlowFiles that were not processed successfully.

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