CODEWITHSUNDEEP
apache-nifi
Michael Glenn
Michael Glenn

Reputation: 421

Specifying null with nifi expression language

I'm trying to replace an empty field with nulls in an UpdateRecord processor.

/title    ${field.value:replaceEmpty(null)}

This fails because "null" is not a valid keyword. How does one specify null in the nifi expression language?

Upvotes: 3

Views: 5720

Answers (3)

barish jain
barish jain

Reputation: 1

It is giving answer as { "fieldname" : "null" }

here null is a string not a null value.

Upvotes: 0

AlvSel
AlvSel

Reputation: 21

There is a trick using RecordPath, if the field value is blank you can do this to get a null value.

  • /fieldName[not(isBlank(/fieldName))]

Upvotes: 1

Andy
Andy

Reputation: 14184

You can use the literal() function to return a String value that is the exact input to the function, and you can nest that inside your replaceEmpty method. Try using the expression ${field.value:replaceEmpty(${literal('null')})}.

If you are doing this in the UpdateRecord processor, you want to use Apache NiFi RecordPath syntax, not Expression Language. I believe the CSVReader and others parse even a field value containing only spaces to empty, so a regular expression like replaceRegex( /title, '^(?![\s\S])$', 'null' ) doesn't work.

My suggestion would be to file a Jira requesting this capability. In the mean time, do not use UpdateRecord for this, but rather ReplaceText with a regular expression like ,\s?, for an empty CSV value and replace it with null.

Upvotes: 1

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