The original implementation was also resilient to empty string (driverJars="").

Splitter.on(',').trimResults().splitToList("");

I get [].

Could NPE happen somewhere else?

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hey Yi,

you are right, NPE is further down:

Caused by: java.lang.NullPointerException: Cannot invoke "String.isEmpty()" because "segment" is null
	java.base/sun.nio.fs.UnixFileSystem.getPath(UnixFileSystem.java:271)
	java.base/java.nio.file.Path.of(Path.java:147)
	java.base/java.nio.file.Paths.get(Paths.java:69)
	org.apache.beam.sdk.io.jdbc.JdbcUtil.lambda$saveFilesLocally$0(JdbcUtil.java:125)
	java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)

when jarPath is empty string my guess is that
ResourceId sourceResourceId = FileSystems.matchNewResource(jarPath, false); returns "/" as CWD is root dir on worker and when this happens Paths.get("/tmp", sourceResourceId.getFilename()) throws npe because sourceResourceId.getFilename() is null.

Thanks for explanation, so the change makes the returned list from [""] to an empty list []. This LGTM