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* 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.flink.streaming.examples.wordcount;
import java.util.StringTokenizer;
import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.examples.java.wordcount.util.WordCountData;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.util.Collector;
/**
* Implements the "WordCount" program that computes a simple word occurrence
* histogram over text files in a streaming fashion.
*
* <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 Flink Streaming program.
* <li>use Tuple data types.
* <li>write and use user-defined functions.
* </ul>
*
*/
public class WordCount {
// *************************************************************************
// PROGRAM
// *************************************************************************
public static void main(String[] args) throws Exception {
if (!parseParameters(args)) {
return;
}
// set up the execution environment
final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
// get input data
DataStream<String> text = getTextDataStream(env);
DataStream<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)
.sum(1);
// emit result
if (fileOutput) {
counts.writeAsText(outputPath, 1);
} else {
counts.print();
}
// execute program
env.execute("Streaming WordCount");
}
// *************************************************************************
// 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 implements FlatMapFunction<String, Tuple2<String, Integer>> {
private static final long serialVersionUID = 1L;
@Override
public void flatMap(String inTuple, Collector<Tuple2<String, Integer>> out)
throws Exception {
// tokenize the line
StringTokenizer tokenizer = new StringTokenizer(inTuple);
// emit the pairs
while (tokenizer.hasMoreTokens()) {
out.collect(new Tuple2<String, Integer>(tokenizer.nextToken(), 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 DataStream<String> getTextDataStream(StreamExecutionEnvironment env) {
if (fileOutput) {
// read the text file from given input path
return env.readTextFile(textPath);
} else {
// get default test text data
return env.fromElements(WordCountData.WORDS);
}
}
}