kafka从头消费数据

从头消费数据需满足两个条件：

1. groupid为新的

2. auto_offset_reset_config的值为earliest

Properties p = new Properties();
        p.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "127.0.0.1:9092");
        p.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        p.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        p.put(ConsumerConfig.GROUP_ID_CONFIG, "abcdefg");
        p.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG,"earliest");
        p.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG,"org.apache.kafka.common.serialization.StringDeserializer");
        p.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,"org.apache.kafka.common.serialization.StringDeserializer");