How deeply does Kafka Streams in Action, Second Edition cover fluent interface?

Explains returned stream objects and demonstrates a complete chain, but does not descend into API internals.

Fluent interface

As explained in Kafka Streams in Action, Second Edition

A fluent interface is an API design pattern in which methods return objects that allow successive operations to be chained in a readable expression.

A fluent interface is an API design pattern that chains method calls into a concise, readable expression. In Kafka Streams, transformations return a new KStream or KTable, so each result can become the receiver for the next operation. section 6.3.1 section 6.2

A Kafka Streams chain typically follows this sequence:

Read records from a topic with builder.stream and Consumed serializers/deserializers. section 6.3.1
Transform values with an operation such as mapValues, receiving another stream. section 6.3.1
Write the final stream to a topic with to and Produced serializers/deserializers. section 6.3.1
Use named intermediate variables when chaining would reduce clarity. section 6.3.1

Uppercase a Kafka stream

KStream<String, String> result = builder.stream("src-topic", Consumed.with(Serdes.String(), Serdes.String())) .mapValues(value -> value.toUpperCase()); result.to("out-topic", Produced.with(Serdes.String(), Serdes.String())); The equivalent fluent form chains the complete topology: builder.stream("src-topic", Consumed.with(Serdes.String(), Serdes.String())).mapValues(value -> value.toUpperCase()).to("out-topic", Produced.with(Serdes.String(), Serdes.String())). section 6.3.1

builder.stream("src-topic", Consumed.with(Serdes.String(), Serdes.String()))
 .mapValues(value -> value.toUpperCase())
 .to("out-topic", Produced.with(Serdes.String(), Serdes.String()));

Inspect the complete one-expression topology to compare fluent chaining with the three-statement version. section 6.3.1

How Kafka Streams in Action, Second Edition covers it

Cover of Kafka Streams in Action, Second Edition

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Related concepts

pipelineuses · A pipeline is an ordered or coordinated sequence of connected processing stages or tasks that passes data, work, or results toward an outcome.
method chaininguses · Method chaining is a programming technique in which successive method calls use the object or value returned by the preceding call.
extensionimplemented by · An extension is a language feature that adds functionality to an existing type without modifying its original definition.
static methodcontrasts with · A static method is a function associated with a type or enclosing scope rather than an object instance, and callable without an instance receiver.

This explainer was generated by Manning's knowledge graph from the text of Kafka Streams in Action, Second Edition. The section links point to the parts of the book it draws on.