[NIFI-8634] Create Controller Services that allows user to choose between Record Readers/Writers based on Expression Language

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Component/s: Extensions
• Assignee: Unassigned
• Reporter: Mark Payne
• Created: 26/May/21 17:13
• Updated: 04/Jun/21 17:09
• Resolved: 04/Jun/21 17:09

Description

Typically when a user builds a flow, the user must choose a JSON Reader, CSV Reader, JSON Writer, CSV Writer, etc. whatever makes sense for their use case.

The downside to this approach is that it makes it difficult to build a flow is more generically distributable.

We should create a RecordReaderLookup service and a RecordWriterLookup service. Each would have a single well-known property for the name of the Record Reader/Writer service to use. User-defined properties would then be used to define those Record Readers/Writers.

For example, one might configure RecordReaderLookup as such:

Selected Reader: #{DataFOrmat}
csv: CSVReader
json: JsonTreeReader
avro: AvroReader 

In this case, CSVReader, JsonTreeReader, and AvroReader are other Record Reader Controller Services. Now, a parameter can be defined with the name DataFormat. If that parameter has a value of csv, the CSVReader would be used. If the parameter has a value of json, the JsonTreeReader would be used, and so forth.

Same principle would be followed for the Record Writer.

Issue Links

• duplicates: NIFI-5829 Create Lookup Controller Services for RecordSetWriter and RecordReader