org.apache.beam.sdk.io.xml.JAXBCoder 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
*
* 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.beam.sdk.io.xml;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Objects;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import org.apache.beam.sdk.coders.CoderException;
import org.apache.beam.sdk.coders.CustomCoder;
import org.apache.beam.sdk.util.EmptyOnDeserializationThreadLocal;
import org.apache.beam.sdk.util.VarInt;
import org.apache.beam.sdk.values.TypeDescriptor;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.io.ByteStreams;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A coder for JAXB annotated objects. This coder uses JAXB marshalling/unmarshalling mechanisms to
* encode/decode the objects. Users must provide the {@code Class} of the JAXB annotated object.
*
* @param type of JAXB annotated objects that will be serialized.
*/
@SuppressWarnings({
"nullness" // TODO(https://github.com/apache/beam/issues/20497)
})
public class JAXBCoder extends CustomCoder {
private final Class jaxbClass;
private transient volatile JAXBContext jaxbContext;
private final EmptyOnDeserializationThreadLocal jaxbMarshaller;
private final EmptyOnDeserializationThreadLocal jaxbUnmarshaller;
public Class getJAXBClass() {
return jaxbClass;
}
private JAXBCoder(Class jaxbClass) {
this.jaxbClass = jaxbClass;
this.jaxbMarshaller =
new EmptyOnDeserializationThreadLocal() {
@Override
protected Marshaller initialValue() {
try {
JAXBContext jaxbContext = getContext();
return jaxbContext.createMarshaller();
} catch (JAXBException e) {
throw new RuntimeException("Error when creating marshaller from JAXB Context.", e);
}
}
};
this.jaxbUnmarshaller =
new EmptyOnDeserializationThreadLocal() {
@Override
protected Unmarshaller initialValue() {
try {
JAXBContext jaxbContext = getContext();
return jaxbContext.createUnmarshaller();
} catch (Exception e) {
throw new RuntimeException("Error when creating unmarshaller from JAXB Context.", e);
}
}
};
}
/**
* Create a coder for a given type of JAXB annotated objects.
*
* @param jaxbClass the {@code Class} of the JAXB annotated objects.
*/
public static JAXBCoder of(Class jaxbClass) {
return new JAXBCoder<>(jaxbClass);
}
@Override
public void encode(T value, OutputStream outStream) throws IOException {
encode(value, outStream, Context.NESTED);
}
@Override
public void encode(T value, OutputStream outStream, Context context) throws IOException {
if (context.isWholeStream) {
try {
jaxbMarshaller.get().marshal(value, new CloseIgnoringOutputStream(outStream));
} catch (JAXBException e) {
throw new CoderException(e);
}
} else {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
jaxbMarshaller.get().marshal(value, baos);
} catch (JAXBException e) {
throw new CoderException(e);
}
VarInt.encode(baos.size(), outStream);
baos.writeTo(outStream);
}
}
@Override
public T decode(InputStream inStream) throws IOException {
return decode(inStream, Context.NESTED);
}
@Override
public T decode(InputStream inStream, Context context) throws IOException {
try {
if (!context.isWholeStream) {
long limit = VarInt.decodeLong(inStream);
inStream = ByteStreams.limit(inStream, limit);
}
@SuppressWarnings("unchecked")
T obj = (T) jaxbUnmarshaller.get().unmarshal(new CloseIgnoringInputStream(inStream));
return obj;
} catch (JAXBException e) {
throw new CoderException(e);
}
}
private JAXBContext getContext() throws JAXBException {
if (jaxbContext == null) {
synchronized (this) {
if (jaxbContext == null) {
jaxbContext = JAXBContext.newInstance(jaxbClass);
}
}
}
return jaxbContext;
}
@Override
public TypeDescriptor getEncodedTypeDescriptor() {
return TypeDescriptor.of(jaxbClass);
}
@Override
public boolean equals(@Nullable Object other) {
if (other == this) {
return true;
}
if (!(other instanceof JAXBCoder)) {
return false;
}
JAXBCoder that = (JAXBCoder) other;
return Objects.equals(this.jaxbClass, that.jaxbClass);
}
@Override
public int hashCode() {
return jaxbClass.hashCode();
}
private static class CloseIgnoringInputStream extends FilterInputStream {
CloseIgnoringInputStream(InputStream in) {
super(in);
}
@Override
public void close() {
// Do nothing. JAXB closes the underlying stream so we must filter out those calls.
}
}
private static class CloseIgnoringOutputStream extends FilterOutputStream {
CloseIgnoringOutputStream(OutputStream out) {
super(out);
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
out.write(b, off, len);
}
@Override
public void close() {
// JAXB closes the underlying stream so we must filter out those calls.
}
}
}