com.google.cloud.dataflow.sdk.values.POutputValueBase Maven / Gradle / Ivy
/*
* Copyright (C) 2015 Google Inc.
*
* Licensed 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 com.google.cloud.dataflow.sdk.values;
import com.google.cloud.dataflow.sdk.Pipeline;
import com.google.cloud.dataflow.sdk.transforms.AppliedPTransform;
/**
* A {@code POutputValueBase} is the abstract base class of
* {@code PTransform} outputs.
*
* A {@code PValueBase} that adds tracking of its producing
* {@code AppliedPTransform}.
*
*
For internal use.
*/
public abstract class POutputValueBase implements POutput {
private final Pipeline pipeline;
protected POutputValueBase(Pipeline pipeline) {
this.pipeline = pipeline;
}
/**
* No-arg constructor for Java serialization only.
* The resulting {@code POutputValueBase} is unlikely to be
* valid.
*/
protected POutputValueBase() {
pipeline = null;
}
@Override
public Pipeline getPipeline() {
return pipeline;
}
/**
* Returns the {@code AppliedPTransform} that this {@code POutputValueBase}
* is an output of.
*
*
For internal use only.
*/
public AppliedPTransform getProducingTransformInternal() {
return producingTransform;
}
/**
* Records that this {@code POutputValueBase} is an output with the
* given name of the given {@code AppliedPTransform}.
*
*
To be invoked only by {@link POutput#recordAsOutput}
* implementations. Not to be invoked directly by user code.
*/
@Override
public void recordAsOutput(AppliedPTransform transform) {
if (producingTransform != null) {
// Already used this POutput as a PTransform output. This can
// happen if the POutput is an output of a transform within a
// composite transform, and is also the result of the composite.
// We want to record the "immediate" atomic transform producing
// this output, and ignore all later composite transforms that
// also produce this output.
//
// Pipeline.applyInternal() uses !hasProducingTransform() to
// avoid calling this operation redundantly, but
// hasProducingTransform() doesn't apply to POutputValueBases
// that aren't PValues or composites of PValues, e.g., PDone.
return;
}
producingTransform = transform;
}
/**
* Default behavior for {@code finishSpecifyingOutput()} is
* to do nothing. Override if your {@link PValue} requires
* finalization.
*/
@Override
public void finishSpecifyingOutput() { }
/**
* The {@code PTransform} that produces this {@code POutputValueBase}.
*/
private AppliedPTransform producingTransform;
}