org.apache.avro.message.RawMessageDecoder Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.avro.message;
import org.apache.avro.AvroRuntimeException;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DecoderFactory;
import java.io.IOException;
import java.io.InputStream;
/**
* A {@link MessageDecoder} that deserializes from raw datum bytes.
*
* This class uses the schema passed to its constructor when decoding buffers.
* To decode buffers that have different schemas, use
* {@link BinaryMessageEncoder} and {@link BinaryMessageDecoder}.
*
* This will not throw {@link BadHeaderException} because it expects no header,
* and will not throw {@link MissingSchemaException} because it always uses the
* read schema from its constructor.
*
* This class is thread-safe.
*/
public class RawMessageDecoder extends MessageDecoder.BaseDecoder {
private static final ThreadLocal DECODER = new ThreadLocal<>();
private final DatumReader reader;
/**
* Creates a new {@link RawMessageDecoder} that uses the given
* {@link GenericData data model} to construct datum instances described by the
* {@link Schema schema}.
*
* The {@code schema} is used as both the expected schema (read schema) and for
* the schema of payloads that are decoded (written schema).
*
* @param model the {@link GenericData data model} for datum instances
* @param schema the {@link Schema} used to construct datum instances and to
* decode buffers.
*/
public RawMessageDecoder(GenericData model, Schema schema) {
this(model, schema, schema);
}
/**
* Creates a new {@link RawMessageDecoder} that uses the given
* {@link GenericData data model} to construct datum instances described by the
* {@link Schema readSchema}.
*
* The {@code readSchema} is used for the expected schema and the
* {@code writeSchema} is the schema used to decode buffers. The
* {@code writeSchema} must be the schema that was used to encode all buffers
* decoded by this class.
*
* @param model the {@link GenericData data model} for datum instances
* @param readSchema the {@link Schema} used to construct datum instances
* @param writeSchema the {@link Schema} used to decode buffers
*/
public RawMessageDecoder(GenericData model, Schema writeSchema, Schema readSchema) {
Schema writeSchema1 = writeSchema;
Schema readSchema1 = readSchema;
this.reader = model.createDatumReader(writeSchema1, readSchema1);
}
@Override
public D decode(InputStream stream, D reuse) {
BinaryDecoder decoder = DecoderFactory.get().directBinaryDecoder(stream, DECODER.get());
DECODER.set(decoder);
try {
return reader.read(reuse, decoder);
} catch (IOException e) {
throw new AvroRuntimeException("Decoding datum failed", e);
}
}
}