org.apache.avro.message.RawMessageEncoder Maven / Gradle / Ivy
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/*
* 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
*
* http://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.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.io.BinaryEncoder;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.EncoderFactory;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
/**
* A {@link MessageEncoder} that encodes only a datum's bytes, without additional
* information (such as a schema fingerprint).
*
* This class is thread-safe.
*/
public class RawMessageEncoder implements MessageEncoder {
private static final ThreadLocal TEMP =
new ThreadLocal() {
@Override
protected BufferOutputStream initialValue() {
return new BufferOutputStream();
}
};
private static final ThreadLocal ENCODER =
new ThreadLocal();
private final Schema writeSchema;
private final boolean copyOutputBytes;
private final DatumWriter writer;
/**
* Creates a new {@link RawMessageEncoder} that uses the given
* {@link GenericData data model} to deconstruct datum instances described by
* the {@link Schema schema}.
*
* Buffers returned by {@link #encode(D)} are copied and will not be modified
* by future calls to {@code encode}.
*
* @param model the {@link GenericData data model} for datum instances
* @param schema the {@link Schema} for datum instances
*/
public RawMessageEncoder(GenericData model, Schema schema) {
this(model, schema, true);
}
/**
* Creates a new {@link RawMessageEncoder} that uses the given
* {@link GenericData data model} to deconstruct datum instances described by
* the {@link Schema schema}.
*
* If {@code shouldCopy} is true, then buffers returned by {@link #encode(D)}
* are copied and will not be modified by future calls to {@code encode}.
*
* If {@code shouldCopy} is false, then buffers returned by {@code encode}
* wrap a thread-local buffer that can be reused by future calls to
* {@code encode}, but may not be. Callers should only set {@code shouldCopy}
* to false if the buffer will be copied before the current thread's next call
* to {@code encode}.
*
* @param model the {@link GenericData data model} for datum instances
* @param schema the {@link Schema} for datum instances
* @param shouldCopy whether to copy buffers before returning encoded results
*/
public RawMessageEncoder(GenericData model, Schema schema, boolean shouldCopy) {
this.writeSchema = schema;
this.copyOutputBytes = shouldCopy;
this.writer = model.createDatumWriter(this.writeSchema);
}
@Override
public ByteBuffer encode(D datum) throws IOException {
BufferOutputStream temp = TEMP.get();
temp.reset();
encode(datum, temp);
if (copyOutputBytes) {
return temp.toBufferWithCopy();
} else {
return temp.toBufferWithoutCopy();
}
}
@Override
public void encode(D datum, OutputStream stream) throws IOException {
BinaryEncoder encoder = EncoderFactory.get()
.directBinaryEncoder(stream, ENCODER.get());
ENCODER.set(encoder);
writer.write(datum, encoder);
encoder.flush();
}
private static class BufferOutputStream extends ByteArrayOutputStream {
BufferOutputStream() {
}
ByteBuffer toBufferWithoutCopy() {
return ByteBuffer.wrap(buf, 0, count);
}
ByteBuffer toBufferWithCopy() {
return ByteBuffer.wrap(toByteArray());
}
}
}