Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.kafka.streams;
import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.kstream.ValueTransformer;
import org.apache.kafka.streams.kstream.ValueTransformerWithKey;
import org.apache.kafka.streams.processor.ProcessorContext;
import org.apache.kafka.streams.state.KeyValueStore;
import org.apache.kafka.streams.state.StoreBuilder;
import org.apache.kafka.streams.state.Stores;
import java.time.Instant;
import java.util.Properties;
public class StreamsDSLAndProcessorExample {
public static void main(String[] args) {
final Properties properties = new Properties();
properties.setProperty(StreamsConfig.APPLICATION_ID_CONFIG, "test-application");
properties.setProperty(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
properties.setProperty(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
properties.setProperty(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
final String storeName = "stateStore";
final StreamsBuilder builder = new StreamsBuilder();
final StoreBuilder<KeyValueStore<String, String>> storeBuilder = Stores.keyValueStoreBuilder(
Stores.persistentKeyValueStore(storeName),
Serdes.String(),
Serdes.String());
builder.addStateStore(storeBuilder);
builder.<String, String>stream("input")
.filter((k,v) -> v.endsWith("FOO"))
.transformValues(() -> new SimpleValueTransformer(storeName), storeName)
.to("output");
final Topology topology = builder.build(properties);
System.out.println(topology.describe());
final KafkaStreams streams = new KafkaStreams(topology, properties);
streams.start();
}
static class SimpleValueTransformer implements ValueTransformerWithKey<String, String, String> {
private String storeName;
private KeyValueStore<String, String> store;
public SimpleValueTransformer(String storeName) {
this.storeName = storeName;
}
@Override
public void init(final ProcessorContext context) {
store = (KeyValueStore) context.getStateStore(storeName);
}
@Override
public String transform(final String key, final String value) {
String persistedValue = store.get(key);
final String updatedValue = value + "_" + Instant.now().toString();
if(persistedValue == null) {
persistedValue = updatedValue;
}
store.put(key, updatedValue);
return persistedValue;
}
@Override
public void close() {
}
}
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.