@nyakkantiOnly processor properties that support the NiFi expression language can be configured to use FlowFile attributes.
Some properties (even if the processor property says supports expression language: false, you may be able to use a simple ${<FlowFile-attribute-name>} to return a value from a attribute key/value pair.
But this is never true for sensitive properties such as password properties. Password properties are especially difficult since those values are encrypted upon apply. So if you entered ${<FlowFile-attribute-name>} , that is what gets encrypted. The processor then decrypts that when making the connection. Nowhere in that process does it ever retrieve a value from the FlowFile.
Thanks,
Matt