我有一个与流有关的apache kafka主题“ historyTopic”：
KStream<Long, byte[]> stream = builder.stream("historyTopic");
我还有一个与流关联的表：
KTable<Long, HistoryObject> table = stream.groupByKey().aggregate(() -> {
return new HistoryObject();
}, (key, value, aggregate) -> {
try {
aggregate.add(deserializeModel(value));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return aggregate;
}, Materialized.with(Serdes.Long(), Serdes.serdeFrom(serializer, deserializer)).as("history-store"));
我希望聚合中的值为byte []，聚合变量为HistoryObject类的对象，在初始化程序中，我首先创建一个新对象，然后在聚合方法中，我希望反序列化byte []值并将其添加到聚合中的列表（HistoryObject），但是出现以下异常：
java.lang.ClassCastException: [B cannot be cast to com.maxflow.historyservice.model.HistoryObject
at org.apache.kafka.streams.kstream.internals.KStreamAggregate$KStreamAggregateProcessor.process(KStreamAggregate.java:91) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:126) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:87) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:302) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.AssignedStreamsTasks.process(AssignedStreamsTasks.java:94) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:409) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.StreamThread.processAndMaybeCommit(StreamThread.java:964) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:832) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:767) ~[kafka-streams-2.0.1.jar:na]
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:736) ~[kafka-streams-2.0.1.jar:na]
deserializeModel方法：
@SuppressWarnings("unchecked")
private static Card deserializeModel(byte[] serialized) throws IOException {
ByteArrayInputStream bis = new ByteArrayInputStream(serialized);
ObjectInput in = null;
Card historyData = null;
try {
in = new ObjectInputStream(bis);
historyData = (Card) in.readObject();
} catch (Exception e) {
e.printStackTrace();
} finally {
bis.close();
}
return historyData;
}
在这种方法中，我将流中的byte []反序列化为Card对象，然后尝试将其从HistoryObject添加到列表中
我的序列化器和反序列化器类如下：
public class HistoryDataValueSerializer implements Closeable, AutoCloseable, Serializer<HistoryObject> {
@SuppressWarnings("unused")
private boolean isKey;
@Override
public void configure(Map<String, ?> configs, boolean isKey)
{
this.isKey = isKey;
}
@Override public byte[] serialize(String arg0, HistoryObject value) {
byte[] retVal = null;
ObjectMapper objectMapper = new ObjectMapper();
try {
retVal = objectMapper.writeValueAsString(value).getBytes();
} catch (Exception e) {
e.printStackTrace();
}
return retVal;
}
@Override
public void close()
{
}
}
public class HistoryDataValueDeserializer implements Closeable, AutoCloseable, Deserializer<HistoryObject> {
@Override
public void configure(Map<String, ?> configs, boolean isKey) {
}
@Override
public HistoryObject deserialize(String s, byte[] value) {
ObjectMapper mapper = new ObjectMapper();
HistoryObject historyObject = null;
try {
historyObject = mapper.readValue(value, HistoryObject.class);
} catch (Exception e) {
e.printStackTrace();
}
return historyObject;
}
@Override
public void close() {
}
}