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NIFI-2556 This closes #868. Updated User Guide with informaiton about custom properties

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Sarah Olson 2016-08-15 14:31:58 -07:00 committed by joewitt
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nifi-docs/src/main/asciidoc/user-guide.adoc
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@ -590,7 +590,37 @@ on the Processor and selecting `Usage' from the context menu. Alternatively, sel
corner of the UI to display a Help page with all of the documentation, including usage documentation
for all the Processors that are available. Click on the desired Processor to view usage documentation.
[[Using_Custom_Properties]]
=== Using Custom Properties with Expression Language
You can use NiFi Expression Language to reference FlowFile attributes, compare them to other values,
and manipulate their values when you are creating and configuring dataflows.
In addition to using FlowFile attributes, system properties, and environment properties within Express
Language, you can also define custom properties for Expression Language use. Defining custom properties
gives you more flexibility in handling and processing dataflows. You can also create custom properties
for connection, server, and service properties, for easier dataflow configuration.
To create custom properties for use with Expression Language, identify one or more sets of key/value
pairs, and give them to your system administrator.
NiFi properties have resolution precedence of which you should be aware when creating custom properties:

* Processor-specific attributes
* FlowFile properties

* FlowFile attributes

* From variable registry:

** User defined properties (custom properties)
** System properties

** Operating System environment variables
When you are creating custom properties, ensure that each custom property contains a distinct property value,
so that it is not overridden by existing environment properties, system properties, or FlowFile attributes.
Once you have added the new custom properties, ensure that you have updated the nifi.variable.registry.properties
field in the nifi.properties file, with the custom properties location.
For more information on Expression Language, see the link:expression-language-guide.html[Expression Lanuaguage Guide].
For information on how to define custom properties, see the link:administration-guide.html[System Administrator’s Guide].
[[Controller_Services_and_Reporting_Tasks]]
=== Controller Services and Reporting Tasks