如何使用java（spring）将文本对象消息生成到kafka主题中？

Question

I want to produce a message into kafka topic. That message should have this pattern:

   {"targetFileInfo":{"path":"2018-05-07-10/row01-small-01.txt.ready"}}

I know that is a json pattern, so how can i convert that json in String?

I use a maven project, so which dependencies are needed to use

 String stringData = JSON.stringify({"targetFileInfo":{"path":"2018-05-07-10/row01-small-01.txt.ready"}});

So I think it is better don't convert Json to string and send indeed that massage into kafka topic.

My Code is like that, it can send a String but i don't know how i can modify my code to send the massage above. maybe you can help me.

 Producer<String, String> producer = null;

    Properties props = new Properties();
    props.put("bootstrap.servers", "localhost:9092");
    props.put("acks", "all");
    props.put("retries", 0);
    props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

    producer = new KafkaProducer<>(props);
    String msg = "welcome";
    producer.send(new ProducerRecord<String, String>("event", msg));

    producer.close();

Answer 1

As per the comment you need to send JsonNode as message on kafka. Write a custom Serializer / Deserializer for the same.

import java.io.IOException;
import java.util.Map;

import org.apache.kafka.common.serialization.Deserializer;
import org.apache.kafka.common.serialization.Serializer;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonNodeSerDes implements Serializer<JsonNode>, Deserializer<JsonNode> {

    private ObjectMapper mapper = new ObjectMapper();

    @Override
    public byte[] serialize(String topic, JsonNode data) {

        try {
            return mapper.writeValueAsBytes(data);
        } catch (JsonProcessingException e) {
            return new byte[0];
        }
    }

    @Override
    public JsonNode deserialize(String topic, byte[] data) {

        try {
            return mapper.readValue(data, JsonNode.class);
        } catch (IOException e) {
            return null;
        }
    }

    @Override
    public void configure(Map<String, ?> configs, boolean isKey) {
    }

    @Override
    public void close() {
    }
}

I wrote serializer / deserializer in the same class. You can separate them in two class (one implementing Serializer , another implementing Deserializer ).

While creating KafkaProducer you need to provide "value.serializer" config and "value.deserializer" config for KafkaConsumer .

External Dependencies used:

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.8.8</version>
</dependency>

Answer 2

That solved my problem:

 Producer<String, String> producer = null;

    Properties props = new Properties();
    props.put("bootstrap.servers", "localhost:9092");
    props.put("acks", "all");
    props.put("retries", 0);
    props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

    producer = new KafkaProducer<>(props);

    try {
        producer = new KafkaProducer<String, String>(props);
    } catch (Exception e) {
        e.printStackTrace();
    }
    blobStorageChecker = new BlobStorageChecker();
    String folder = blobStorageChecker.getCurrentDateUTC();
    String msg = "{\"targetFileInfo\":{\"path\":\"test/"+folder+"row01-small.txt\"},\"sourceFileInfo\":{\"lastModifiedTime\":1525437960000,\"file\":\"/row01-small-01.txt\",\"filename\":\"/data/row01/row01-small.txt\",\"size\":19728,\"remoteUri\":\"ftp://waws-prod-am2-191.ftp.net/data/orsted-real/inbound/row01\",\"contentEncoding\":\"\",\"contentType\":\"\"}}";
    ProducerRecord<String, String> record = new ProducerRecord<String, String>("event-orsted-v1", null, msg);
    if (producer != null) {
        try {
            Future<RecordMetadata> future = producer.send(record);
            RecordMetadata metadata = future.get();
        } catch (Exception e) {
            System.err.println(e.getMessage());
            e.printStackTrace();
        }
    }
    producer.close();