/*
* 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.runners.flink;
import org.apache.beam.sdk.Pipeline;
/**
* The role of this class is to translate the Beam operators to
* their Flink counterparts. If we have a streaming job, this is instantiated as a
* {@link FlinkStreamingPipelineTranslator}. In other case, i.e. for a batch job,
* a {@link FlinkBatchPipelineTranslator} is created. Correspondingly, the
* {@link org.apache.beam.sdk.values.PCollection}-based user-provided job is translated into
* a {@link org.apache.flink.streaming.api.datastream.DataStream} (for streaming) or a
* {@link org.apache.flink.api.java.DataSet} (for batch) one.
*/
abstract class FlinkPipelineTranslator extends Pipeline.PipelineVisitor.Defaults {
/**
* Translates the pipeline by passing this class as a visitor.
* @param pipeline The pipeline to be translated
*/
public void translate(Pipeline pipeline) {
pipeline.traverseTopologically(this);
}
/**
* Utility formatting method.
* @param n number of spaces to generate
* @return String with "|" followed by n spaces
*/
protected static String genSpaces(int n) {
StringBuilder builder = new StringBuilder();
for (int i = 0; i < n; i++) {
builder.append("| ");
}
return builder.toString();
}
}