src/main/java/org/apache/giraph/examples/VertexWithComponentTextOutputFormat.java

/*
* 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,
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* See the License for the specific language governing permissions and
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*/

package org.apache.giraph.examples;

import org.apache.giraph.graph.BasicVertex;
import org.apache.giraph.graph.VertexWriter;
import org.apache.giraph.lib.TextVertexOutputFormat;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

import java.io.IOException;

/**
 * Text-based {@link org.apache.giraph.graph.VertexOutputFormat} for usage with
 * {@link ConnectedComponentsVertex}
 *
 * Each line consists of a vertex and its associated component (represented by the smallest
 * vertex id in the component)
 */
public class VertexWithComponentTextOutputFormat extends
        TextVertexOutputFormat<IntWritable, IntWritable, NullWritable> {

    @Override
    public VertexWriter<IntWritable, IntWritable, NullWritable>
            createVertexWriter(TaskAttemptContext context)
            throws IOException, InterruptedException {
        RecordWriter<Text, Text> recordWriter =
                textOutputFormat.getRecordWriter(context);
        return new VertexWithComponentWriter(recordWriter);
    }

    public static class VertexWithComponentWriter extends
            TextVertexOutputFormat.TextVertexWriter<IntWritable, IntWritable,
            NullWritable> {

        public VertexWithComponentWriter(RecordWriter<Text, Text> writer) {
            super(writer);
        }

        @Override
        public void writeVertex(BasicVertex<IntWritable, IntWritable,
                NullWritable,?> vertex) throws IOException,
                InterruptedException {
            StringBuilder output = new StringBuilder();
            output.append(vertex.getVertexId().get());
            output.append('\t');
            output.append(vertex.getVertexValue().get());
            getRecordWriter().write(new Text(output.toString()), null);
        }

    }
}