Avro无法直接对带有逻辑类型的字段进行反序列化,因为Avro默认不支持逻辑类型。但是,可以通过自定义逻辑类型解决此问题。以下是一个示例代码,演示如何自定义逻辑类型和相应的解析器来实现对带有逻辑类型的字段进行反序列化:
首先,我们需要定义一个自定义逻辑类型。例如,我们可以创建一个名为DateLogicalType
的逻辑类型,用于表示日期类型:
import org.apache.avro.LogicalType;
import org.apache.avro.Schema;
import org.apache.avro.SchemaBuilder;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.Decoder;
import org.apache.avro.io.Encoder;
import org.apache.avro.io.ResolvingDecoder;
import org.apache.avro.io.ResolvingEncoder;
import org.apache.avro.reflect.CustomEncoding;
import org.apache.avro.reflect.CustomResolving;
import java.io.IOException;
import java.util.Date;
public class DateLogicalType extends LogicalType {
public DateLogicalType() {
super("date");
}
@Override
public Schema addToSchema(Schema schema) {
return SchemaBuilder.builder().intType().logicalType(this).build();
}
}
然后,我们需要创建一个自定义解析器来处理带有逻辑类型的字段。在解析器中,我们需要实现CustomResolving
接口,并覆盖read
和write
方法:
public class DateLogicalTypeResolver implements CustomResolving {
@Override
public void resolve(Schema.Field field, List schemaPath) {
field.addProp("logicalType", "date");
}
@Override
public Object read(Object old, Decoder in, Schema schema, ResolvingDecoder resolver) throws IOException {
int value = in.readInt();
return new Date(value);
}
@Override
public void write(Object datum, Encoder out, ResolvingEncoder resolver) throws IOException {
Date date = (Date) datum;
out.writeInt((int) date.getTime());
}
}
现在,我们可以使用自定义逻辑类型和解析器对带有逻辑类型的字段进行反序列化。以下是一个示例代码,演示如何在Avro中使用自定义逻辑类型和解析器:
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.*;
import org.apache.avro.reflect.ReflectData;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Date;
public class AvroLogicalTypeExample {
public static void main(String[] args) throws IOException {
// 创建带有逻辑类型的Schema
Schema schema = ReflectData.get().getSchema(DateRecord.class);
schema.addProp("avro.java.custom.encoding", "date");
schema.addProp("avro.java.custom.resolver", DateLogicalTypeResolver.class.getName());
// 创建GenericRecord对象
GenericRecord record = new GenericData.Record(schema);
record.put("dateField", new Date());
// 序列化
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
BinaryEncoder encoder = EncoderFactory.get().binaryEncoder(outputStream, null);
DatumWriter writer = new GenericDatumWriter<>(schema);
writer.write(record, encoder);
encoder.flush();
outputStream.close();
byte[] serializedData = outputStream.toByteArray();
// 反序列化
BinaryDecoder decoder = DecoderFactory.get().binaryDecoder(new ByteArrayInputStream(serializedData), null);
DatumReader reader = new GenericDatumReader<>(schema);
GenericRecord deserializedRecord = reader.read(null, decoder);
// 输出反序列化结果
System.out.println("Deserialized record: " + deserializedRecord.get("dateField"));
}
public static class DateRecord {
private Date dateField;
public Date getDateField() {
return dateField;
}
public void setDateField(Date dateField) {
this.dateField = dateField;
}
}
}
在上述示例代码中,我们首先创建了一个带有逻辑类型的Schema,并使用addProp
方法添加了自定义编码器和解析器的属性