/*
* 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.coders;
import java.util.List;
import org.apache.beam.sdk.values.TypeDescriptor;
import org.apache.beam.sdk.values.TypeParameter;
/**
* A {@link Coder} for {@link List}, using the format of {@link IterableLikeCoder}.
*
* @param <T> the type of the elements of the Lists being transcoded
*/
public class ListCoder<T> extends IterableLikeCoder<T, List<T>> {
public static <T> ListCoder<T> of(Coder<T> elemCoder) {
return new ListCoder<>(elemCoder);
}
/////////////////////////////////////////////////////////////////////////////
// Internal operations below here.
@Override
protected final List<T> decodeToIterable(List<T> decodedElements) {
return decodedElements;
}
protected ListCoder(Coder<T> elemCoder) {
super(elemCoder, "List");
}
/**
* List sizes are always known, so ListIterable may be deterministic while
* the general IterableLikeCoder is not.
*/
@Override
public void verifyDeterministic() throws NonDeterministicException {
verifyDeterministic(this, "ListCoder.elemCoder must be deterministic", getElemCoder());
}
@Override
public TypeDescriptor<List<T>> getEncodedTypeDescriptor() {
return new TypeDescriptor<List<T>>(getClass()) {}.where(
new TypeParameter<T>() {}, getElemCoder().getEncodedTypeDescriptor());
}
}