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https://issues.apache.org/jira/browse/NIFI-7147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pierre Villard resolved NIFI-7147.
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Resolution: Feedback Received
Apache NiFi 1.x is no longer maintained and no new release is planned on the
1.x release line. Marking as resolved as part of a cleanup operation. Please
open a new one with an updated description if this is still relevant for NiFi
2.x.
> ReplaceText processor strips backslashes with regex replace
> -----------------------------------------------------------
>
> Key: NIFI-7147
> URL: https://issues.apache.org/jira/browse/NIFI-7147
> Project: Apache NiFi
> Issue Type: Bug
> Components: Extensions
> Affects Versions: 1.11.1
> Reporter: Denes Arvay
> Priority: Major
>
> ReplaceText processor strips backslashes if the Replacement Strategy is Regex
> Replace and the Replacement Value contains expression and backreference.
> I was able to reduce the problem to the following example:
> - Search Value: {{(.)}}
> - Replacement Value: {{${'$1'}}}
> - Input: {{\a}}
> - Expected output: {{\a}}
> - Actual output: {{a}} -> the backslash has been removed
> I did some investigation and the cause seems to be the usage of
> {{Matcher.matcher.appendReplacement}} at [1], which according to the
> documentation [2] treats backslashes (and dollar signs) in a special manner:
> _"Note that backslashes (\) and dollar signs ($) in the replacement string
> may cause the results to be different than if it were being treated as a
> literal replacement string."_
> See the following example, it's very similar to what happens at [1] when
> running with the example above.
> {code:java}
> Matcher matcher = Pattern.compile("(.)").matcher("A");
> matcher.find();
> matcher.appendReplacement(sb, "\\a");
> {code}
> The result is {{a}} in the StringBuilder, not {{\a}} as I would expect at
> first. If the backslash in {{\a}} is escaped (i.e. {{\\a}}) the result is
> {{\a}}.
> This issue relates to NIFI-5813 and it seems the
> {{normalizeReplacementString}} method [3] works incorrectly: in NIFI-5813 it
> escapes things it shouldn't while it doesn't escape what it should.
> [1]
> https://github.com/apache/nifi/blob/rel/nifi-1.11.1/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/ReplaceText.java#L555
> [2]
> https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/regex/Matcher.html#appendReplacement(java.lang.StringBuffer,java.lang.String)
> [3]
> https://github.com/apache/nifi/blob/rel/nifi-1.11.1/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/ReplaceText.java#L681
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