/***********************************************************************************************************************
*
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* 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 eu.stratosphere.example.java.wordcount;
import eu.stratosphere.api.java.DataSet;
import eu.stratosphere.api.java.ExecutionEnvironment;
import eu.stratosphere.api.java.aggregation.Aggregations;
import eu.stratosphere.api.java.functions.FlatMapFunction;
import eu.stratosphere.api.java.tuple.Tuple2;
import eu.stratosphere.example.java.wordcount.util.WordCountData;
import eu.stratosphere.util.Collector;
/**
* Implements the "WordCount" program that computes a simple word occurrence histogram
* over text files.
*
* <p>
* The input is a plain text file with lines separated by newline characters.
*
* <p>
* Usage: <code>WordCount <text path> <result path></code><br>
* If no parameters are provided, the program is run with default data from {@link WordCountData}.
*
* <p>
* This example shows how to:
* <ul>
* <li>write a simple Stratosphere program.
* <li>use Tuple data types.
* <li>write and use user-defined functions.
* </ul>
*
*/
@SuppressWarnings("serial")
public class WordCount {
// *************************************************************************
// PROGRAM
// *************************************************************************
public static void main(String[] args) throws Exception {
if(!parseParameters(args)) {
return;
}
// set up the execution environment
final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
// get input data
DataSet<String> text = getTextDataSet(env);
DataSet<Tuple2<String, Integer>> counts =
// split up the lines in pairs (2-tuples) containing: (word,1)
text.flatMap(new Tokenizer())
// group by the tuple field "0" and sum up tuple field "1"
.groupBy(0)
.aggregate(Aggregations.SUM, 1);
// emit result
if(fileOutput) {
counts.writeAsCsv(outputPath, "\n", " ");
} else {
counts.print();
}
// execute program
env.execute("WordCount Example");
}
// *************************************************************************
// USER FUNCTIONS
// *************************************************************************
/**
* Implements the string tokenizer that splits sentences into words as a user-defined
* FlatMapFunction. The function takes a line (String) and splits it into
* multiple pairs in the form of "(word,1)" (Tuple2<String, Integer>).
*/
public static final class Tokenizer extends FlatMapFunction<String, Tuple2<String, Integer>> {
@Override
public void flatMap(String value, Collector<Tuple2<String, Integer>> out) {
// normalize and split the line
String[] tokens = value.toLowerCase().split("\\W+");
// emit the pairs
for (String token : tokens) {
if (token.length() > 0) {
out.collect(new Tuple2<String, Integer>(token, 1));
}
}
}
}
// *************************************************************************
// UTIL METHODS
// *************************************************************************
private static boolean fileOutput = false;
private static String textPath;
private static String outputPath;
private static boolean parseParameters(String[] args) {
if(args.length > 0) {
// parse input arguments
fileOutput = true;
if(args.length == 2) {
textPath = args[0];
outputPath = args[1];
} else {
System.err.println("Usage: WordCount <text path> <result path>");
return false;
}
} else {
System.out.println("Executing WordCount example with built-in default data.");
System.out.println(" Provide parameters to read input data from a file.");
System.out.println(" Usage: WordCount <text path> <result path>");
}
return true;
}
private static DataSet<String> getTextDataSet(ExecutionEnvironment env) {
if(fileOutput) {
// read the text file from given input path
return env.readTextFile(textPath);
} else {
// get default test text data
return WordCountData.getDefaultTextLineDataSet(env);
}
}
}