不能将Apache flink Confluent org.apache.avro.generic.GenericData$Record转换为java.lang.String

import org.apache.avro.Schema;

String schemaString = "{\"type\":\"record\",\"name\":\"MyRecord\",\"fields\":[{\"name\":\"field1\",\"type\":\"string\"}]}";
Schema schema = new Schema.Parser().parse(schemaString);

import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericRecord;

GenericRecord record = new GenericData.Record(schema);
record.put("field1", "value1");

import org.apache.flink.api.common.serialization.SerializationSchema;
import org.apache.flink.api.common.serialization.DeserializationSchema;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.java.typeutils.TypeExtractor;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.flink.util.Preconditions;

public class AvroSerializationSchema<T> implements SerializationSchema<T>, DeserializationSchema<T> {
    private final Class<T> recordClass;
    private final ObjectMapper objectMapper;

    public AvroSerializationSchema(Class<T> recordClass) {
        Preconditions.checkNotNull(recordClass, "Record class must not be null.");
        this.recordClass = recordClass;
        this.objectMapper = new ObjectMapper();
    }

    @Override
    public byte[] serialize(T element) {
        try {
            return objectMapper.writeValueAsBytes(element);
        } catch (Exception e) {
            throw new RuntimeException("Failed to serialize record: " + element, e);
        }
    }

    @Override
    public T deserialize(byte[] message) {
        try {
            return objectMapper.readValue(message, recordClass);
        } catch (Exception e) {
            throw new RuntimeException("Failed to deserialize message.", e);
        }
    }

    @Override
    public boolean isEndOfStream(T nextElement) {
        return false;
    }

    @Override
    public TypeInformation<T> getProducedType() {
        return TypeExtractor.getForClass(recordClass);
    }
}

import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;

DataStream<GenericRecord> sourceStream = ... ; // 输入流
DataStream<GenericRecord> resultStream = sourceStream
        .map(record -> {
            // 进行相应的转换操作
            return record;
        })
        .returns(TypeInformation.of(GenericRecord.class));

resultStream.addSink(...); // 输出到其他地方