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merged 2 commits into from
Nov 11, 2025
Merged

Rehaul of streams intro section #740

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2dd83d4
Add prev/next navigation buttons sorted by page weights
hvishwanath Nov 9, 2025
2b3f466
Rehaul of streams introduction. Supporting css, shortcodes etc.,
hvishwanath Nov 11, 2025
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52 changes: 52 additions & 0 deletions assets/scss/_variables_project_after_bs.scss
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Original file line number Diff line number Diff line change
Expand Up @@ -26,3 +26,55 @@ ul.dropdown-menu {
border: 1px solid #bdbdbd;
}

/* Pager button explicit neutral styling to avoid theme primary/orange overrides */
.pager-btn {
border: 3px solid #dee2e6 !important; /* gray-300 */
color: #343a40 !important; /* text-dark */
background-color: #ffffff !important; /* white background */
box-shadow: 0 .25rem .5rem rgba(0,0,0,.05) !important; /* subtle */
}
.pager-btn:hover {
background-color: #f8f9fa !important; /* gray-100 */
border-color: #ced4da !important; /* gray-400 */
text-decoration: none !important;
}
.pager-btn:focus {
outline: 0 !important;
box-shadow: 0 0 0 .2rem rgba(206,212,218,.5) !important; /* gray focus ring */
}

.carousel-item {
min-height: 400px;

.youtube-video {
max-width: 800px;
margin: 0 auto;
}

h4 {
color: var(--td-body-text-color);
}
}

.carousel-control-prev,
.carousel-control-next {
width: 5%;
opacity: 0.8;

&:hover {
opacity: 1;
}
}

/* Make carousel nav buttons more obvious */
.carousel-control-prev-icon,
.carousel-control-next-icon {
background-color: rgba(0, 0, 0, 0.65);
border-radius: 50%;
padding: 1.1rem;
box-shadow: 0 .5rem 1rem rgba(0, 0, 0, 0.15);
}
.carousel-control-prev:hover .carousel-control-prev-icon,
.carousel-control-next:hover .carousel-control-next-icon {
background-color: rgba(0, 0, 0, 0.85);
}
249 changes: 128 additions & 121 deletions content/en/0110/streams/introduction.md
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Expand Up @@ -31,131 +31,138 @@ type: docs

The code example below implements a WordCount application that is elastic, highly scalable, fault-tolerant, stateful, and ready to run in production at large scale

Java 8+ Java 7 Scala


import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.KStreamBuilder;
import org.apache.kafka.streams.kstream.KTable;

import java.util.Arrays;
import java.util.Properties;

public class WordCountApplication {

public static void main(final String[] args) throws Exception {
Properties config = new Properties();
config.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application");
config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka-broker1:9092");
config.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
config.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());

KStreamBuilder builder = new KStreamBuilder();
KStream<String, String> textLines = builder.stream("TextLinesTopic");
KTable<String, Long> wordCounts = textLines
.flatMapValues(textLine -> Arrays.asList(textLine.toLowerCase().split("\W+")))
.groupBy((key, word) -> word)
.count("Counts");
wordCounts.to(Serdes.String(), Serdes.Long(), "WordsWithCountsTopic");

KafkaStreams streams = new KafkaStreams(builder, config);
streams.start();
}

{{< tabpane >}}
{{% tab header="Java 8+ Java 7" %}}
```java
import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.KStreamBuilder;
import org.apache.kafka.streams.kstream.KTable;

import java.util.Arrays;
import java.util.Properties;

public class WordCountApplication {

public static void main(final String[] args) throws Exception {
Properties config = new Properties();
config.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application");
config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka-broker1:9092");
config.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
config.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());

KStreamBuilder builder = new KStreamBuilder();
KStream<String, String> textLines = builder.stream("TextLinesTopic");
KTable<String, Long> wordCounts = textLines
.flatMapValues(textLine -> Arrays.asList(textLine.toLowerCase().split("\W+")))
.groupBy((key, word) -> word)
.count("Counts");
wordCounts.to(Serdes.String(), Serdes.Long(), "WordsWithCountsTopic");

KafkaStreams streams = new KafkaStreams(builder, config);
streams.start();
}


import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.KStreamBuilder;
import org.apache.kafka.streams.kstream.KTable;
import org.apache.kafka.streams.kstream.KeyValueMapper;
import org.apache.kafka.streams.kstream.ValueMapper;

import java.util.Arrays;
import java.util.Properties;

public class WordCountApplication {
public static void main(final String[] args) throws Exception {
Properties config = new Properties();
config.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application");
config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka-broker1:9092");
config.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
config.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());

KStreamBuilder builder = new KStreamBuilder();
KStream<String, String> textLines = builder.stream("TextLinesTopic");
KTable<String, Long> wordCounts = textLines
.flatMapValues(new ValueMapper<String, Iterable<String>>() {
@Override
public Iterable<String> apply(String textLine) {
return Arrays.asList(textLine.toLowerCase().split("\W+"));
}
})
.groupBy(new KeyValueMapper<String, String, String>() {
@Override
public String apply(String key, String word) {
return word;
}
})
.count("Counts");
wordCounts.to(Serdes.String(), Serdes.Long(), "WordsWithCountsTopic");

KafkaStreams streams = new KafkaStreams(builder, config);
streams.start();
}


}


import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.KStreamBuilder;
import org.apache.kafka.streams.kstream.KTable;
import org.apache.kafka.streams.kstream.KeyValueMapper;
import org.apache.kafka.streams.kstream.ValueMapper;

import java.util.Arrays;
import java.util.Properties;

public class WordCountApplication {

public static void main(final String[] args) throws Exception {
Properties config = new Properties();
config.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application");
config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka-broker1:9092");
config.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
config.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());

KStreamBuilder builder = new KStreamBuilder();
KStream<String, String> textLines = builder.stream("TextLinesTopic");
KTable<String, Long> wordCounts = textLines
.flatMapValues(new ValueMapper<String, Iterable<String>>() {
@Override
public Iterable<String> apply(String textLine) {
return Arrays.asList(textLine.toLowerCase().split("\W+"));
}
})
.groupBy(new KeyValueMapper<String, String, String>() {
@Override
public String apply(String key, String word) {
return word;
}
})
.count("Counts");
wordCounts.to(Serdes.String(), Serdes.Long(), "WordsWithCountsTopic");

KafkaStreams streams = new KafkaStreams(builder, config);
streams.start();
}



import java.lang.Long
import java.util.Properties
import java.util.concurrent.TimeUnit

import org.apache.kafka.common.serialization._
import org.apache.kafka.streams._
import org.apache.kafka.streams.kstream.{KStream, KStreamBuilder, KTable}

import scala.collection.JavaConverters.asJavaIterableConverter

object WordCountApplication {

def main(args: Array[String]) {
val config: Properties = {
val p = new Properties()
p.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application")
p.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka-broker1:9092")
p.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass)
p.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass)
p
}

val builder: KStreamBuilder = new KStreamBuilder()
val textLines: KStream[String, String] = builder.stream("TextLinesTopic")
val wordCounts: KTable[String, Long] = textLines
.flatMapValues(textLine => textLine.toLowerCase.split("\W+").toIterable.asJava)
.groupBy((_, word) => word)
.count("Counts")
wordCounts.to(Serdes.String(), Serdes.Long(), "WordsWithCountsTopic")

val streams: KafkaStreams = new KafkaStreams(builder, config)
streams.start()

Runtime.getRuntime.addShutdownHook(new Thread(() => {
streams.close(10, TimeUnit.SECONDS)
}))

}



import java.lang.Long
```
{{% /tab %}}
{{% tab header="Scala" %}}
```scala
import java.util.Properties
import java.util.concurrent.TimeUnit

import org.apache.kafka.common.serialization._
import org.apache.kafka.streams._
import org.apache.kafka.streams.kstream.{KStream, KStreamBuilder, KTable}

import scala.collection.JavaConverters.asJavaIterableConverter

object WordCountApplication {

def main(args: Array[String]) {
val config: Properties = {
val p = new Properties()
p.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application")
p.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka-broker1:9092")
p.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass)
p.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass)
p
}


val builder: KStreamBuilder = new KStreamBuilder()
val textLines: KStream[String, String] = builder.stream("TextLinesTopic")
val wordCounts: KTable[String, Long] = textLines
.flatMapValues(textLine => textLine.toLowerCase.split("\W+").toIterable.asJava)
.groupBy((_, word) => word)
.count("Counts")
wordCounts.to(Serdes.String(), Serdes.Long(), "WordsWithCountsTopic")

val streams: KafkaStreams = new KafkaStreams(builder, config)
streams.start()

Runtime.getRuntime.addShutdownHook(new Thread(() => {
streams.close(10, TimeUnit.SECONDS)
}))
}


}
```
{{% /tab %}}
{{< /tabpane >}}


## See how Kafka Streams is being used

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