我正在尝试在 kafka 流中使用 kafka connect api 消费 json 消息。 我尝试在 google 中搜索，但找不到任何有关如何在 Streams api 中读取 json 消息的实质性信息。
因此，凭借有限的知识，我尝试了以下方法。
package com.kafka.api.serializers.json;
import java.util.Properties;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.ForeachAction;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.KStreamBuilder;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
public class ConsumerUtilities {
private static ObjectMapper om = new ObjectMapper();
public static Properties getProperties() {
Properties configs = new Properties();
configs.put(StreamsConfig.APPLICATION_ID_CONFIG,
"Kafka test application");
configs.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
configs.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG,
"org.apache.kafka.common.serialization.ByteArraySerializer");
configs.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG,
"org.apache.kafka.connect.json.JsonDeserializer");
return configs;
}
public static KStreamBuilder getStreamingConsumer() {
KStreamBuilder builder = new KStreamBuilder();
return builder;
}
public static void printStreamData() {
KStreamBuilder builder = getStreamingConsumer();
KStream<String, JsonNode> kStream = builder.stream("test");
kStream.foreach(new ForeachAction<String, JsonNode>() {
@Override
public void apply(String key, JsonNode value) {
try {
System.out.println(key + " : " + om.treeToValue(value, Person.class));
} catch (JsonProcessingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
KafkaStreams kafkaStreams = new KafkaStreams(builder, getProperties());
kafkaStreams.start();
}
}
package com.kafka.api.serializers.json;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;
import java.util.Properties;
public class ProducerUtilities {
private static ObjectMapper om = new ObjectMapper();
public static org.apache.kafka.clients.producer.Producer<String, JsonNode> getProducer() {
Properties configProperties = new Properties();
configProperties.put(ProducerConfig.CLIENT_ID_CONFIG,
"kafka json producer");
configProperties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,
"localhost:9092");
configProperties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG,
"org.apache.kafka.common.serialization.ByteArraySerializer");
configProperties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,
"org.apache.kafka.connect.json.JsonSerializer");
org.apache.kafka.clients.producer.Producer<String, JsonNode> producer = new KafkaProducer<String, JsonNode>(
configProperties);
return producer;
}
public ProducerRecord<String,JsonNode> createRecord(Person person){
JsonNode jsonNode = om.valueToTree(person);
ProducerRecord<String,JsonNode> record = new ProducerRecord<String,JsonNode>("test",jsonNode);
return record;
}
}
当我执行代码时，我收到如下异常
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] ERROR org.apache.kafka.clients.consumer.internals.ConsumerCoordinator - User provided listener org.apache.kafka.streams.processor.internals.StreamThread$RebalanceListener for group Kafka test application failed on partition assignment
org.apache.kafka.streams.errors.StreamsException: Failed to configure value serde class org.apache.kafka.connect.json.JsonDeserializer
at org.apache.kafka.streams.StreamsConfig.defaultValueSerde(StreamsConfig.java:770)
at org.apache.kafka.streams.processor.internals.AbstractProcessorContext.<init>(AbstractProcessorContext.java:59)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.<init>(ProcessorContextImpl.java:40)
at org.apache.kafka.streams.processor.internals.StreamTask.<init>(StreamTask.java:138)
at org.apache.kafka.streams.processor.internals.StreamThread.createStreamTask(StreamThread.java:1078)
at org.apache.kafka.streams.processor.internals.StreamThread$TaskCreator.createTask(StreamThread.java:255)
at org.apache.kafka.streams.processor.internals.StreamThread$AbstractTaskCreator.createTasks(StreamThread.java:245)
at org.apache.kafka.streams.processor.internals.StreamThread.addStreamTasks(StreamThread.java:1147)
at org.apache.kafka.streams.processor.internals.StreamThread.access$800(StreamThread.java:68)
at org.apache.kafka.streams.processor.internals.StreamThread$RebalanceListener.onPartitionsAssigned(StreamThread.java:184)
at org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.onJoinComplete(ConsumerCoordinator.java:265)
at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.joinGroupIfNeeded(AbstractCoordinator.java:367)
at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.ensureActiveGroup(AbstractCoordinator.java:316)
at org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.poll(ConsumerCoordinator.java:297)
at org.apache.kafka.clients.consumer.KafkaConsumer.pollOnce(KafkaConsumer.java:1078)
at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1043)
at org.apache.kafka.streams.processor.internals.StreamThread.pollRequests(StreamThread.java:536)
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:490)
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:480)
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:457)
Caused by: org.apache.kafka.common.KafkaException: org.apache.kafka.connect.json.JsonDeserializer is not an instance of org.apache.kafka.common.serialization.Serde
at org.apache.kafka.common.config.AbstractConfig.getConfiguredInstance(AbstractConfig.java:248)
at org.apache.kafka.streams.StreamsConfig.defaultValueSerde(StreamsConfig.java:764)
... 19 more
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] INFO org.apache.kafka.streams.processor.internals.StreamThread - stream-thread [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] Shutting down
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] INFO org.apache.kafka.streams.processor.internals.StreamThread - stream-thread [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] State transition from PARTITIONS_ASSIGNED to PENDING_SHUTDOWN.
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] INFO org.apache.kafka.clients.producer.KafkaProducer - Closing the Kafka producer with timeoutMillis = 9223372036854775807 ms.
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] INFO org.apache.kafka.streams.processor.internals.StreamThread - stream-thread [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] Stream thread shutdown complete
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] INFO org.apache.kafka.streams.processor.internals.StreamThread - stream-thread [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] State transition from PENDING_SHUTDOWN to DEAD.
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] WARN org.apache.kafka.streams.KafkaStreams - stream-client [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29] All stream threads have died. The Kafka Streams instance will be in an error state and should be closed.
[Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] INFO org.apache.kafka.streams.KafkaStreams - stream-client [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29] State transition from REBALANCING to ERROR.
Exception in thread "Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1" org.apache.kafka.streams.errors.StreamsException: stream-thread [Kafka test application-d3a307c9-d998-421f-829c-85532efc8b29-StreamThread-1] Failed to rebalance.
at org.apache.kafka.streams.processor.internals.StreamThread.pollRequests(StreamThread.java:543)
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:490)
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:480)
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:457)
Caused by: org.apache.kafka.streams.errors.StreamsException: Failed to configure value serde class org.apache.kafka.connect.json.JsonDeserializer
at org.apache.kafka.streams.StreamsConfig.defaultValueSerde(StreamsConfig.java:770)
at org.apache.kafka.streams.processor.internals.AbstractProcessorContext.<init>(AbstractProcessorContext.java:59)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.<init>(ProcessorContextImpl.java:40)
at org.apache.kafka.streams.processor.internals.StreamTask.<init>(StreamTask.java:138)
at org.apache.kafka.streams.processor.internals.StreamThread.createStreamTask(StreamThread.java:1078)
at org.apache.kafka.streams.processor.internals.StreamThread$TaskCreator.createTask(StreamThread.java:255)
at org.apache.kafka.streams.processor.internals.StreamThread$AbstractTaskCreator.createTasks(StreamThread.java:245)
at org.apache.kafka.streams.processor.internals.StreamThread.addStreamTasks(StreamThread.java:1147)
at org.apache.kafka.streams.processor.internals.StreamThread.access$800(StreamThread.java:68)
at org.apache.kafka.streams.processor.internals.StreamThread$RebalanceListener.onPartitionsAssigned(StreamThread.java:184)
at org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.onJoinComplete(ConsumerCoordinator.java:265)
at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.joinGroupIfNeeded(AbstractCoordinator.java:367)
at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.ensureActiveGroup(AbstractCoordinator.java:316)
at org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.poll(ConsumerCoordinator.java:297)
at org.apache.kafka.clients.consumer.KafkaConsumer.pollOnce(KafkaConsumer.java:1078)
at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1043)
at org.apache.kafka.streams.processor.internals.StreamThread.pollRequests(StreamThread.java:536)
... 3 more
Caused by: org.apache.kafka.common.KafkaException: org.apache.kafka.connect.json.JsonDeserializer is not an instance of org.apache.kafka.common.serialization.Serde
at org.apache.kafka.common.config.AbstractConfig.getConfiguredInstance(AbstractConfig.java:248)
at org.apache.kafka.streams.StreamsConfig.defaultValueSerde(StreamsConfig.java:764)
... 19 more
我正在寻找一些指导来解决该问题。
根据 Matthias 建议创建自定义序列化器和反序列化器
package com.kafka.api.utilities;
import java.util.Properties;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.ForeachAction;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.KStreamBuilder;
import com.kafka.api.models.Person;
import com.kafka.api.serdes.JsonDeserializer;
import com.kafka.api.serdes.JsonSerializer;
import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.common.serialization.Serde;
public class ConsumerUtilities {
//private static ObjectMapper om = new ObjectMapper();
public static Properties getProperties() {
Properties configs = new Properties();
configs.put(StreamsConfig.APPLICATION_ID_CONFIG,
"Kafka test application");
configs.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
// configs.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG,
// "org.apache.kafka.common.serialization.ByteArraySerializer");
// configs.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG,
// "org.apache.kafka.connect.json.JsonDeserializer");
return configs;
}
public static KStreamBuilder getStreamingConsumer() {
KStreamBuilder builder = new KStreamBuilder();
return builder;
}
public static void printStreamData() {
JsonSerializer<Person> personJsonSerializer = new JsonSerializer<>();
JsonDeserializer<Person> personJsonDeserializer = new JsonDeserializer<>(Person.class);
Serde<Person> personSerde = Serdes.serdeFrom(personJsonSerializer, personJsonDeserializer);
KStreamBuilder builder = getStreamingConsumer();
KStream<String, Person> kStream = builder.stream(Serdes.String(),personSerde , "test");
kStream.foreach(new ForeachAction<String, Person>() {
@Override
public void apply(String key, Person value) {
System.out.println(key + " : " + value.toString());
}
});
KafkaStreams kafkaStreams = new KafkaStreams(builder, getProperties());
kafkaStreams.start();
}
}
package com.kafka.api.serdes;
import java.util.Map;
import org.apache.kafka.common.errors.SerializationException;
import org.apache.kafka.common.serialization.Deserializer;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JsonDeserializer<T> implements Deserializer<T>{
private ObjectMapper om = new ObjectMapper();
private Class<T> type;
/*
* Default constructor needed by kafka
*/
public JsonDeserializer(Class<T> type) {
this.type = type;
}
@Override
public void close() {
// TODO Auto-generated method stub
}
@SuppressWarnings("unchecked")
@Override
public void configure(Map<String, ?> map, boolean arg1) {
if(type == null){
type = (Class<T>) map.get("type");
}
}
@Override
public T deserialize(String undefined, byte[] bytes) {
if(bytes == null || bytes.length == 0){
return null;
}
try{
return om.readValue(bytes, type);
}catch(Exception e){
throw new SerializationException(e);
}
}
protected Class<T> getType(){
return type;
}
}
package com.kafka.api.serdes;
import java.util.Map;
import org.apache.kafka.common.errors.SerializationException;
import org.apache.kafka.common.serialization.Serializer;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JsonSerializer<T> implements Serializer<T> {
private ObjectMapper om = new ObjectMapper();
@Override
public void close() {
// TODO Auto-generated method stub
}
@Override
public void configure(Map<String, ?> config, boolean isKey) {
// TODO Auto-generated method stub
}
@Override
public byte[] serialize(String topic, T data) {
// TODO Auto-generated method stub
try {
return om.writeValueAsBytes(data);
} catch (JsonProcessingException e) {
throw new SerializationException();
}
}
}
异常:执行流应用程序后，我收到以下异常。我很困惑。
[Kafka test application-cee84455-78ca-4a2f-881a-89b3c3a00e4b-StreamThread-1] INFO org.apache.kafka.streams.KafkaStreams - stream-client [Kafka test application-cee84455-78ca-4a2f-881a-89b3c3a00e4b] State transition from RUNNING to ERROR.
Exception in thread "Kafka test application-cee84455-78ca-4a2f-881a-89b3c3a00e4b-StreamThread-1" org.apache.kafka.streams.errors.StreamsException: Failed to deserialize value for record. topic=test, partition=0, offset=0
at org.apache.kafka.streams.processor.internals.SourceNodeRecordDeserializer.deserialize(SourceNodeRecordDeserializer.java:46)
at org.apache.kafka.streams.processor.internals.RecordQueue.addRawRecords(RecordQueue.java:84)
at org.apache.kafka.streams.processor.internals.PartitionGroup.addRawRecords(PartitionGroup.java:117)
at org.apache.kafka.streams.processor.internals.StreamTask.addRecords(StreamTask.java:483)
at org.apache.kafka.streams.processor.internals.StreamThread.addRecordsToTasks(StreamThread.java:604)
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:512)
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:480)
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:457)
Caused by: org.apache.kafka.common.errors.SerializationException: com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'hello': was expecting ('true', 'false' or 'null')
at [Source: [B@5ee179dc; line: 1, column: 11]
Caused by: com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'hello': was expecting ('true', 'false' or 'null')
at [Source: [B@5ee179dc; line: 1, column: 11]
at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1702)
at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:558)
at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._reportInvalidToken(UTF8StreamJsonParser.java:3524)
at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._handleUnexpectedValue(UTF8StreamJsonParser.java:2686)
at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._nextTokenNotInObject(UTF8StreamJsonParser.java:878)
at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextToken(UTF8StreamJsonParser.java:772)
at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3834)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3783)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2929)
at com.kafka.api.serdes.JsonDeserializer.deserialize(JsonDeserializer.java:43)
at org.apache.kafka.common.serialization.ExtendedDeserializer$Wrapper.deserialize(ExtendedDeserializer.java:65)
at org.apache.kafka.common.serialization.ExtendedDeserializer$Wrapper.deserialize(ExtendedDeserializer.java:55)
at org.apache.kafka.streams.processor.internals.SourceNode.deserializeValue(SourceNode.java:56)
at org.apache.kafka.streams.processor.internals.SourceNodeRecordDeserializer.deserialize(SourceNodeRecordDeserializer.java:44)
at org.apache.kafka.streams.processor.internals.RecordQueue.addRawRecords(RecordQueue.java:84)
at org.apache.kafka.streams.processor.internals.PartitionGroup.addRawRecords(PartitionGroup.java:117)
at org.apache.kafka.streams.processor.internals.StreamTask.addRecords(StreamTask.java:483)
at org.apache.kafka.streams.processor.internals.StreamThread.addRecordsToTasks(StreamThread.java:604)
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:512)
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:480)
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:457)
最佳答案
Streams API 需要读写数据，因此它使用了 Serde 的抽象。它同时是序列化器和反序列化器的包装器。这就是异常的基本含义。
Caused by: org.apache.kafka.common.KafkaException: org.apache.kafka.connect.json.JsonDeserializer is not an instance of org.apache.kafka.common.serialization.Serde
因此，您需要包装 JsonSerializer和JsonDeserialzier进入JsonSerde并使用这个 JsonSerde在StreamsConfig .
最简单的方法是使用 Serdes.serdeFrom(...)方法(注:Serdes——复数)。作为替代方案，您还可以实现 Serde直接接口(interface)(注Serde——单数)。您可以在 Serdes 中找到示例关于如何实现的类(class) Serde界面。
关于java - 在 kafka 流中使用 kafka connect json api 消费 JSON 值 : JAVA，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46565829/