NiFi ExecuteScript example to lookup a configure path from an external xml file.

config.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration verbose="false" debugMode="false">
    <dataFlows>
        <dataFlow>
            <properties>
                <dept>salary</dept>
                <version>1.0</version>
            </properties>
            <filePattern>salary_.*.gz</filePattern>
            <to>
                <path>d_${dept}/${version}/csv</path>
            </to>
        </dataFlow>
        <dataFlow>
            <properties>
                <dept>pension</dept>
                <version>2.2</version>
            </properties>
            <filePattern>pension_.*.gz</filePattern>
            <to>
                <path>d_${dept}/${version}/csv</path>
            </to>
        </dataFlow>
    </dataFlows>
</configuration>

FindToPath.groovy

import java.util.regex.Pattern
import org.apache.nifi.attribute.expression.language.Query
import org.apache.nifi.flowfile.FlowFile

FlowFile flowFile = session.get()
if (!flowFile) return

def filename = flowFile.getAttribute('filename')
def configuration = new XmlSlurper().parse("/tmp/config.xml")

def dataFlow = configuration.dataFlows.dataFlow.find { Pattern.compile(it.filePattern.text()).matcher(filename).matches() }

if (dataFlow.isEmpty()) {
    session.transfer(flowFile, REL_FAILURE)
    return
}

def variables = [:]
variables['dept'] = dataFlow.properties.dept.text()
variables['version'] = dataFlow.properties.version.text()
def query = Query.prepare(dataFlow.to.path.text())
def path = query.evaluateExpressions(variables, null)

flowFile = session.putAttribute(flowFile, 'to.path', path)

session.transfer(flowFile, REL_SUCCESS)