[NIFI-4720] Expression Language guide explanation of order of evaluating an attribute is out of date

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Won't Do
• Component/s: Documentation & Website
• Assignee: Unassigned
• Reporter: Joe Percivall
• Created: 22/Dec/17 01:31
• Updated: 18/Sep/23 18:16
• Resolved: 18/Sep/23 18:16

Description

In the Expression Language guide, under "Structure of a NiFi Expression"[1], it explains the order in which the different sources of attribute values are processed but doesn't include recent updates to EL. Essentially, this should summarize the resolution precedence stated in the User Guide[2].

In this example, the value to be returned is the value of the "my attribute" value, if it exists. If that attribute does not exist, the Expression Language will then look for a System Environment Variable named "my attribute." If unable to find this, it will look for a JVM System Property named "my attribute." Finally, if none of these exists, the Expression Language will return a null value.

[1] https://nifi.apache.org/docs/nifi-docs/html/expression-language-guide.html#structure
[2] https://nifi.apache.org/docs/nifi-docs/html/user-guide.html#Using_Custom_Properties