Scala Reactive Programming

The Akka Streams Flow component

In the Akka Streams API, Flow is a connector or mediator between Source and Sink for streaming data and has one input and one output.

Akka Streams' Flow is used to connect a Source to a Sink and is responsible for doing one or more of the following operations:

• Analyzing data elements
• Updating/reading/deleting data elements
• Transforming data elements into a required format
• Grouping/mapping/filtering data elements and more

In the Akka Streams API, Flow is defined as a final class in the akka.stream.scaladsl package, as shown here:

final class Flow[-In, +Out, +Mat] {  
  // Both In (Input) and Out (Output) 
} 

We can understand this Flow component by going through the following diagram:

Unlike the Source and Sink ...