Daniel Stieglitz created NIFI-10396:
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Summary: Expression Language jsonPath throws error instead of
returning empty string when subject is invalid JSON
Key: NIFI-10396
URL: https://issues.apache.org/jira/browse/NIFI-10396
Project: Apache NiFi
Issue Type: Bug
Components: Core Framework
Affects Versions: 1.17.0
Reporter: Daniel Stieglitz
Attachments: JsonPathInvalidJsonYieldsFlowFiles.xml
Per the [Expression Language
documentation|https://nifi.apache.org/docs/nifi-docs/html/expression-language-guide.html#jsonpath]
for jsonPath "An empty string is generated if the Subject does not contain
valid JSON, the _jsonPath_ is invalid, or the path does not exist in the
Subject." Further in the documentation it states "An empty subject value or a
subject value with an invalid JSON document results in an exception bulletin."
This would seem to indicate with invalid JSON an empty string is returned and
the processor which is handling the Expression Language will get an empty
string and not have to yield any flow files. Attached is a template which
indicates that instead of a returned empty string, an exception is thrown and
the processor is yielding flow files causing its queue to backup.
The attached template [^JsonPathInvalidJsonYieldsFlowFiles.xml]
uses a RouteOnAttributeProcessor to determine whether an attribute value is
valid JSON or not. Two Expression Language expressions are used both of which
use JsonPath of $ (which should return the whole JSON document) chained with
isEmpty():not() or isEmpty() to determine if the attribute value is valid JSON
or not.
Note how the flow file with a valid JSON attribute is routed correctly while
the flow file with invalid JSON is yielded and not routed correctly. Instead of
routing to the invalid relationship the flow files are backing up in the queue.
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