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# Kafka

[Apache Kafka](https://kafka.apache.org/)  是一个开源的分布式事件流平台，被数千家公司用于高性能数据管道、流分析、数据集成和关键任务应用。

## 示例代码

### kafka 生产者生产数据 Java 代码示例

```java
    Properties props = new Properties();
    props.put("bootstrap.servers", "127.0.0.1:9092");
    props.put("key.serializer", StringSerializer.class);
    props.put("value.serializer", StringSerializer.class);
    KafkaProducer<String, String> producer = new KafkaProducer<>(props);
    producer.send(
        new ProducerRecord<>(
            "Kafka-Test", "key", "root.kafka," + System.currentTimeMillis() + ",value,INT32,100"));
    producer.close();
```

### kafka 消费者接收数据 Java 代码示例

```java
    Properties props = new Properties();
    props.put("bootstrap.servers", "127.0.0.1:9092");
    props.put("key.deserializer", StringDeserializer.class);
    props.put("value.deserializer", StringDeserializer.class);
    props.put("auto.offset.reset", "earliest");
    props.put("group.id", "Kafka-Test");
    KafkaConsumer<String, String> kafkaConsumer = new KafkaConsumer<>(props);
    kafkaConsumer.subscribe(Collections.singleton("Kafka-Test"));
    ConsumerRecords<String, String> records = kafkaConsumer.poll(Duration.ofSeconds(1));
 ```

### 存入 IoTDB 服务器的 Java 代码示例

```java
    SessionPool pool =
        new SessionPool.Builder()
            .host("127.0.0.1")
            .port(6667)
            .user("root")
            .password("root")
            .maxSize(3)
            .build();
    List<String> datas = new ArrayList<>(records.count());
    for (ConsumerRecord<String, String> record : records) {
      datas.add(record.value());
    }        
    int size = datas.size();
    List<String> deviceIds = new ArrayList<>(size);
    List<Long> times = new ArrayList<>(size);
    List<List<String>> measurementsList = new ArrayList<>(size);
    List<List<TSDataType>> typesList = new ArrayList<>(size);
    List<List<Object>> valuesList = new ArrayList<>(size);
    for (String data : datas) {
      String[] dataArray = data.split(",");
      String device = dataArray[0];
      long time = Long.parseLong(dataArray[1]);
      List<String> measurements = Arrays.asList(dataArray[2].split(":"));
      List<TSDataType> types = new ArrayList<>();
      for (String type : dataArray[3].split(":")) {
        types.add(TSDataType.valueOf(type));
      }
      List<Object> values = new ArrayList<>();
      String[] valuesStr = dataArray[4].split(":");
      for (int i = 0; i < valuesStr.length; i++) {
        switch (types.get(i)) {
          case INT64:
            values.add(Long.parseLong(valuesStr[i]));
            break;
          case DOUBLE:
            values.add(Double.parseDouble(valuesStr[i]));
            break;
          case INT32:
            values.add(Integer.parseInt(valuesStr[i]));
            break;
          case TEXT:
            values.add(valuesStr[i]);
            break;
          case FLOAT:
            values.add(Float.parseFloat(valuesStr[i]));
            break;
          case BOOLEAN:
            values.add(Boolean.parseBoolean(valuesStr[i]));
            break;
        }
      }
      deviceIds.add(device);
      times.add(time);
      measurementsList.add(measurements);
      typesList.add(types);
      valuesList.add(values);
    }
    pool.insertRecords(deviceIds, times, measurementsList, typesList, valuesList);
 ```