There seems to be a bug in the file reader node, that means that a valid URL needs to be manually set, even though the URL is controlled by a variable. Leaving the value blank results in a "Invalid settings: java.lang.NullPointerException".
The issue is solved by selecting a valid file manually (the file reader will still read the file set by a variable), but seems to be a bit unnecessary.
Thanks for pointing this out. This is true for all nodes, which means the node configuration need to be valid before switching to the Flow Variable tab.
This bug workaround is ok in windows but fails on MAC. Steps to reproduce:
- Select a file in file reader -> preview data looks fine
- Click variable v=? and select location as the flow variable
- the file name from step 1 disappeared making it impossible to save the changes.
UPDATE: I needed to execute the loop start first before changing the file reader to the variable. The file reader then grabs the first iteration of the variable to fill out the field and you can save the node.