In NIFI I am trying to create a custom processor, SO I want to fetch all the properties entered by the user. So how can I create and fetch those properties in custom processor.
The user-defined properties are available in your ProcessContext like all properties are, but they have a flag for being dynamic. Here's a snippet for iterating over the user-defined properties:
Fill in the lambda in the forEach() with your logic for handling the properties. (This is taken from my SO answer for the same question)