/*
* 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.values;
import java.util.Collections;
import java.util.Map;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.WriteFiles;
import org.apache.beam.sdk.transforms.PTransform;
/**
* {@link PDone} is the output of a {@link PTransform} that has a trivial result,
* such as a {@link WriteFiles}.
*/
public class PDone implements POutput {
private final Pipeline pipeline;
private PDone(Pipeline pipeline) {
this.pipeline = pipeline;
}
/**
* Creates a {@link PDone} in the given {@link Pipeline}.
*/
public static PDone in(Pipeline pipeline) {
return new PDone(pipeline);
}
@Override
public Pipeline getPipeline() {
return pipeline;
}
/**
* A {@link PDone} contains no {@link PValue PValues}.
*/
@Override
public Map<TupleTag<?>, PValue> expand() {
return Collections.emptyMap();
}
/** Does nothing; there is nothing to finish specifying. */
@Override
public void finishSpecifyingOutput(
String transformName, PInput input, PTransform<?, ?> transform) {}
}