Provides the user with the ability to take a nested JSON document and flatten it into a simple key/value pair document. The keys are combined at each level with a user-defined separator that defaults to '.'. Support three kinds of flatten mode, normal, keep-arrays and dot notation for MongoDB query. Default flatten mode is 'keep-arrays'.


json, flatten


In the list below, the names of required properties appear in bold. Any other properties (not in bold) are considered optional. The table also indicates any default values, and whether a property supports the NiFi Expression Language.

NameDefault ValueAllowable ValuesDescription
Separator.The separator character used for joining keys. Must be a JSON-legal character.
Supports Expression Language: true (will be evaluated using flow file attributes and variable registry)
Flatten Modekeep arrays
  • normal Flattens every objects into a single level json
  • keep arrays Flattens every objects and keep arrays format
  • dot notation Conforms to MongoDB dot notation to update also nested documents
Specifies how json is flattened


successSuccessfully flattened files go to this relationship.
failureFiles that cannot be flattened go to this relationship.

Reads Attributes:

None specified.

Writes Attributes:

None specified.

State management:

This component does not store state.


This component is not restricted.

System Resource Considerations:

None specified.