/StreamsDSLAndProcessorExample.java
Forked from bbejeck/StreamsDSLAndProcessorExample.java
Created Apr 26, 2019
/* | |
* 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() { | |
} | |
} | |
} |
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