/*
* 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.HashSet;
import java.util.List;
import java.util.Set;
import org.apache.beam.sdk.values.TypeDescriptor;
import org.apache.beam.sdk.values.TypeParameter;
/**
* A {@link SetCoder} encodes any {@link Set} using the format of {@link IterableLikeCoder}. The
* elements may not be in a deterministic order, depending on the {@code Set} implementation.
*
* @param <T> the type of the elements of the set
*/
public class SetCoder<T> extends IterableLikeCoder<T, Set<T>> {
/**
* Produces a {@link SetCoder} with the given {@code elementCoder}.
*/
public static <T> SetCoder<T> of(Coder<T> elementCoder) {
return new SetCoder<>(elementCoder);
}
/**
* {@inheritDoc}
*
* @throws NonDeterministicException always. Sets are not ordered, but
* they are encoded in the order of an arbitrary iteration.
*/
@Override
public void verifyDeterministic() throws NonDeterministicException {
throw new NonDeterministicException(this,
"Ordering of elements in a set may be non-deterministic.");
}
@Override
public TypeDescriptor<Set<T>> getEncodedTypeDescriptor() {
return new TypeDescriptor<Set<T>>() {}.where(
new TypeParameter<T>() {}, getElemCoder().getEncodedTypeDescriptor());
}
/////////////////////////////////////////////////////////////////////////////
// Internal operations below here.
/**
* {@inheritDoc}
*
* @return A new {@link Set} built from the elements in the {@link List} decoded by
* {@link IterableLikeCoder}.
*/
@Override
protected final Set<T> decodeToIterable(List<T> decodedElements) {
return new HashSet<>(decodedElements);
}
protected SetCoder(Coder<T> elemCoder) {
super(elemCoder, "Set");
}
}