content: /*
   * 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.processor;
  
  import org.apache.kafka.common.serialization.IntegerDeserializer;
  import org.apache.kafka.common.serialization.IntegerSerializer;
  import org.apache.kafka.common.serialization.Serdes;
  import org.apache.kafka.common.serialization.StringDeserializer;
  import org.apache.kafka.common.serialization.StringSerializer;
  import org.apache.kafka.streams.KeyValue;
  import org.apache.kafka.streams.TestInputTopic;
  import org.apache.kafka.streams.TestOutputTopic;
  import org.apache.kafka.streams.Topology;
  import org.apache.kafka.streams.TopologyTestDriver;
  import org.apache.kafka.streams.processor.api.Processor;
  import org.apache.kafka.streams.processor.api.ProcessorContext;
  import org.apache.kafka.streams.processor.api.Record;
  import org.apache.kafka.streams.state.KeyValueIterator;
  import org.apache.kafka.streams.state.KeyValueStore;
  import org.apache.kafka.streams.state.Stores;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.LinkedList;
  import java.util.List;
  
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.equalTo;
  
  public class ReadOnlyStoreTest {
  
      @Test
      public void shouldConnectProcessorAndWriteDataToReadOnlyStore() {
          final Topology topology = new Topology();
          topology.addReadOnlyStateStore(
              Stores.keyValueStoreBuilder(
                  Stores.inMemoryKeyValueStore("readOnlyStore"),
                  new Serdes.IntegerSerde(),
                  new Serdes.StringSerde()
              ),
              "readOnlySource",
              new IntegerDeserializer(),
              new StringDeserializer(),
              "storeTopic",
              "readOnlyProcessor",
              () -> new Processor<>() {
                  KeyValueStore<Integer, String> store;
  
                  @Override
                  public void init(final ProcessorContext<Void, Void> context) {
                      store = context.getStateStore("readOnlyStore");
                  }
                  @Override
                  public void process(final Record<Integer, String> record) {
                      store.put(record.key(), record.value());
                  }
              }
          );
  
          topology.addSource("source", new IntegerDeserializer(), new StringDeserializer(), "inputTopic");
          topology.addProcessor(
              "processor",
              () -> new Processor<Integer, String, Integer, String>() {
                  ProcessorContext<Integer, String> context;
                  KeyValueStore<Integer, String> store;
  
                  @Override
                  public void init(final ProcessorContext<Integer, String> context) {
                      this.context = context;
                      store = context.getStateStore("readOnlyStore");
                  }
  
                  @Override
                  public void process(final Record<Integer, String> record) {
                      context.forward(record.withValue(
                          record.value() + " -- " + store.get(record.key())
                      ));
                  }
              },
              "source"
          );
          topology.connectProcessorAndStateStores("processor", "readOnlyStore");
          topology.addSink("sink", "outputTopic", new IntegerSerializer(), new StringSerializer(), "processor");
  
          try (final TopologyTestDriver driver = new TopologyTestDriver(topology)) {
              final TestInputTopic<Integer, String> readOnlyStoreTopic =
                  driver.createInputTopic("storeTopic", new IntegerSerializer(), new StringSerializer());
              final TestInputTopic<Integer, String> input =
                  driver.createInputTopic("inputTopic", new IntegerSerializer(), new StringSerializer());
              final TestOutputTopic<Integer, String> output =
                  driver.createOutputTopic("outputTopic", new IntegerDeserializer(), new StringDeserializer());
  
              readOnlyStoreTopic.pipeInput(1, "foo");
              readOnlyStoreTopic.pipeInput(2, "bar");
  
              input.pipeInput(1, "bar");
              input.pipeInput(2, "foo");
  
              final KeyValueStore<Integer, String> store = driver.getKeyValueStore("readOnlyStore");
  
              try (final KeyValueIterator<Integer, String> it = store.all()) {
                  final List<KeyValue<Integer, String>> storeContent = new LinkedList<>();
                  it.forEachRemaining(storeContent::add);
  
                  final List<KeyValue<Integer, String>> expectedResult = new LinkedList<>();
                  expectedResult.add(KeyValue.pair(1, "foo"));
                  expectedResult.add(KeyValue.pair(2, "bar"));
  
                  assertThat(storeContent, equalTo(expectedResult));
              }
  
              final List<KeyValue<Integer, String>> expectedResult = new LinkedList<>();
              expectedResult.add(KeyValue.pair(1, "bar -- foo"));
              expectedResult.add(KeyValue.pair(2, "foo -- bar"));
  
              assertThat(output.readKeyValuesToList(), equalTo(expectedResult));
          }
      }
  }
  