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Streams Code Examples

If you’re new to Kafka Streams, here is a curated list of resources to get you started.

Getting started examples

GitHub Repos

The kafka-streams-examples GitHub repo is a curated repo with examples that demonstrate the use of Kafka Streams DSL, the low-level Processor API, Java 8 lambda expressions, reading and writing Avro data, and implementing unit tests with TopologyTestDriver and end-to-end integration tests using embedded Kafka clusters.

Java

With lambda expressions for Java 8+:

• WordCountLambdaExample
• AnomalyDetectionLambdaExample
• GlobalKTablesExample
• MapFunctionLambdaExample
• PageViewRegionLambdaExample
• UserRegionLambdaExample
• WikipediaFeedAvroLambdaExample
• ApplicationResetExample
• SessionWindowsExample
• SumLambdaExample
• TopArticlesLambdaExample

Without lambda expressions for Java 7+:

• PageViewRegionExample
• WikipediaFeedAvroExample

Scala

• MapFunctionScalaExample

Security examples

Java programming language

Without lambda expressions for Java 7:

• SecureKafkaStreamsExample

Interactive Queries examples

Since Confluent Platform 3.1+ and Kafka 0.10.1+, it is possible to query state stores created via the Kafka Streams DSL and the Processor API. Please refer to Interactive Queries for further information.

Java

With lambda expressions for Java 8+:

• WordCountInteractiveQueriesExample
• KafkaMusicExample

End-to-end application examples

These demo applications use embedded instances of Kafka, ZooKeeper, and Confluent Schema Registry. They are implemented as integration tests.

See also

To see end-to-end examples of Kafka Streams applications deployed in an event streaming platform with all the services in Confluent Platform and interconnecting other end systems, refer to confluentinc/examples.

Java

With lambda expressions for Java 8+:

• WordCountLambdaIntegrationTest
• FanoutLambdaIntegrationTest
• GenericAvroIntegrationTest
• GlobalKTablesExampleTest
• HandlingCorruptedInputRecordsIntegrationTest
• MapFunctionLambdaIntegrationTest
• MixAndMatchLambdaIntegrationTest – how to mix the DSL and the Processor API
• SpecificAvroIntegrationTest
• StateStoresInTheDSLIntegrationTest – how to use state stores in the DSL
• StreamToStreamJoinIntegrationTest
• StreamToTableJoinIntegrationTest
• TableToTableJoinIntegrationTest
• UserCountsPerRegionLambdaIntegrationTest
• ApplicationResetIntegrationTest
• EventDeduplicationLambdaIntegrationTest
• SumLambdaIntegrationTest
• TopArticlesLambdaExampleTest

Without lambda expressions for Java 7:

• PassThroughIntegrationTest

Scala

• StreamToTableJoinScalaIntegrationTest
• ProbabilisticCountingScalaIntegrationTest - demonstrates how to probabilistically count items in an input stream by implementing a custom state store that is backed by a Count-Min Sketch data structure
• GenericAvroScalaIntegrationTest
• SpecificAvroScalaIntegrationTest
• WordCountScalaIntegrationTest

Event-Driven Microservice example

Java

The Event-Driven Microservice example implements an Orders Service that provides a REST interface to POST and GET orders. Posting an order creates an event in Kafka, which is picked up by three different validation engines: a Fraud Service, an Inventory Service, and an Order Details Service. These services validate the order in parallel, emitting a PASS or FAIL based on whether each validation succeeds.

• Microservices example source code
• Microservices example tests
• Self-paced Kafka Streams tutorial based on the microservices example above: deployed in an event streaming platform with all the services in Confluent Platform and interconnecting other end systems