Force UTF-8 encoding in `JsonLogHandler` of `kafka-fetcher-plugin`. (#9927)

docs/en/changes/changes.md

@@ -103,6 +103,7 @@
 * Fix `ClassCastException` in `LoggingConfigWatcher`.
 * Support span attached event concept in Zipkin and SkyWalking trace query.
 * Support span attached events on Zipkin lens UI.
+* Force UTF-8 encoding in `JsonLogHandler` of `kafka-fetcher-plugin`.
 
 #### UI
 

oap-server/server-fetcher-plugin/kafka-fetcher-plugin/src/main/java/org/apache/skywalking/oap/server/analyzer/agent/kafka/provider/handler/JsonLogHandler.java

@@ -19,6 +19,7 @@ package org.apache.skywalking.oap.server.analyzer.agent.kafka.provider.handler;
 
 import java.io.IOException;
 
+import java.nio.charset.StandardCharsets;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.kafka.clients.consumer.ConsumerRecord;
 import org.apache.kafka.common.utils.Bytes;
@@ -50,7 +51,7 @@ public class JsonLogHandler extends LogHandler {
     @Override
     protected LogData parseConsumerRecord(ConsumerRecord<String, Bytes> record) throws IOException {
         LogData.Builder logDataBuilder = LogData.newBuilder();
-        ProtoBufJsonUtils.fromJSON(record.value().toString(), logDataBuilder);
+        ProtoBufJsonUtils.fromJSON(new String(record.value().get(), StandardCharsets.UTF_8), logDataBuilder);
         return logDataBuilder.build();
     }
 }