Create a Nifi flow using a GroovyScript processor

We are using Groovy for many of our Apache Nifi flows. Based on the below article I would like to create a Nifi flow using a GroovyScript processor. The flow / processor would be used to take a (template) XLSX file and a configuration to fill cells in the Excel sheet with data. https://community.cloudera.com/t5/Community-Articles/Use-NiFi-to-process-Excel-spreadsheets-in-automated/ta-p/247529 I would like to create the following processor: - the groovy processor receives a JSON object and a file name to process. The json looks something like this (can be changed if that is easier): { input: 'inputfile.xlsx', output: 'outputfile.xlsx', mutations: [{ sheetname: 'thesheet', cellname: 'B11', value: 42 },{ sheetname: 'thesheet', cellname: 'C2', value: 'text content' }] } - The script opens the xlsx file from the filesystem - Based on the mutations array, the Groovy script processor makes changes to the cells using the Apache POI API - The flow saves the xlsx file back on the filesystem.