HashMap<String, String> kafkaParams = new HashMap<>();
kafkaParams.put("metadata.broker.list", "localhost:9092");

String topics = "test4";
HashSet<String> topicsSet = new HashSet<String>(Arrays.asList(topics.split(" ")));

JavaDStream<String> stream1 = KafkaUtils.createDirectStream(jssc, String.class, String.class, StringDecoder.class,
    StringDecoder.class, kafkaParams, topicsSet)
    .transformToPair(new Function<JavaPairRDD<String, String>, JavaPairRDD<String, String>>() {
      @Override
      public JavaPairRDD<String, String> call(JavaPairRDD<String, String> rdd) {
        rdd.saveAsTextFile("output");
        return rdd;
      }
    }).map(new Function<Tuple2<String, String>, String>() {
      @Override
      public String call(Tuple2<String, String> kv) {
        return kv._2();
      }
    });
stream1.print();
jssc.start();
jssc.awaitTermination();

交叉检查主题“test4”中是否有有效数据。

我期望从kafka集群流式传输的字符串在控制台中打印。控制台中没有异常，但也没有输出。我有什么遗漏吗？