Question

我使用kafka-mqtt连接器从mqtt代理收到有关kafka主题的消息。然后，我在使用kafka消费者时从kafka主题阅读了此消息。当我打印消息时，这就是结果。我如何正确阅读消息？

这是用于设置使用者和创建流的代码。

SparkConf sparkConf = new SparkConf().setAppName("GestoreSoccorso").setMaster("local[2]");
JavaStreamingContext ssc = new JavaStreamingContext(sparkConf, new Duration(500));

Map<String, Object> kafkaParams = new HashMap<>();
kafkaParams.put("bootstrap.servers", "10.0.4.215:9092");
kafkaParams.put("key.deserializer", StringDeserializer.class);
kafkaParams.put("value.deserializer", StringDeserializer.class);
kafkaParams.put("group.id", "use_a_separate_group_id_for_each_stream");
kafkaParams.put("auto.offset.reset", "earliest");
kafkaParams.put("enable.auto.commit", false);
Collection<String> topics = Arrays.asList("ankioverdrive_v1_events");

JavaInputDStream<ConsumerRecord<String, String>> stream =
        KafkaUtils.createDirectStream(
                ssc,
                LocationStrategies.PreferConsistent(),
                ConsumerStrategies.<String, String>Subscribe(topics, kafkaParams)
        );

然后这是我用来读取主题消息并打印它们的代码。

stream.foreachRDD(new VoidFunction<JavaRDD<ConsumerRecord<String, String>>>() {
            @Override
            public void call(JavaRDD<ConsumerRecord<String, String>> consumerRecordJavaRDD) throws Exception {
                consumerRecordJavaRDD.foreach(new VoidFunction<ConsumerRecord<String, String>>() {
                    @Override
                    public void call(ConsumerRecord<String, String> stringStringConsumerRecord) throws Exception {
                        String stringa=stringStringConsumerRecord.value();
                        System.out.println(DEBUG+"DATI RICEVUTI -> "+ stringa);

最后这是输出

DEBUG: DATI RICEVUTI ->     ܑ�՛Y
SKULL   �    unknown0%

Answer 1

您为参数key.deserializer和value.deserializer传递了错误的值。

代替

kafkaParams.put("key.deserializer", StringDeserializer.class);
kafkaParams.put("value.deserializer", StringDeserializer.class);

您需要通过

kafkaParams.put("key.deserializer", StringDeserializer.class.getName());
kafkaParams.put("value.deserializer", StringDeserializer.class.getName());

或简单地

kafkaParams.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
kafkaParams.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

解码消息Kafka-mqtt

1 个答案: