examples/wordcount/src/main/java/org/apache/apex/examples/wordcount/WordReader.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, 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.apex.examples.wordcount;

import java.util.regex.Pattern;

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.common.util.BaseOperator;

/**
 * Extracts words from input line
 *
 * @since 3.3.0
 */
public class WordReader extends BaseOperator
{
  // default pattern for word-separators
  private static final Pattern nonWordDefault = Pattern.compile("[\\p{Punct}\\s]+");

  private String nonWordStr;              // configurable regex
  private transient Pattern nonWord;      // compiled regex

  /**
   * Output port on which words from the current file are emitted
   */
  public final transient DefaultOutputPort<String> output = new DefaultOutputPort<>();

  /**
   * Input port on which lines from the current file are received
   */
  public final transient DefaultInputPort<String> input = new DefaultInputPort<String>()
  {

    @Override
    public void process(String line)
    {
      // line; split it into words and emit them
      final String[] words = nonWord.split(line);
      for (String word : words) {
        if (word.isEmpty()) {
          continue;
        }
        output.emit(word);
      }
    }
  };

  /**
   * Returns the regular expression that matches strings between words
   * @return Regular expression for strings that separate words
   */
  public String getNonWordStr()
  {
    return nonWordStr;
  }

  /**
   * Sets the regular expression that matches strings between words
   * @param regex New regular expression for strings that separate words
   */
  public void setNonWordStr(String regex)
  {
    nonWordStr = regex;
  }

  /**
   * {@inheritDoc}
   * Set nonWord to the default pattern if necessary
   */
  @Override
  public void setup(OperatorContext context)
  {
    if (null == nonWordStr) {
      nonWord = nonWordDefault;
    } else {
      nonWord = Pattern.compile(nonWordStr);
    }
  }

}