opennlp.tools.ml.model.FileEventStream Maven / Gradle / Ivy
/*
* 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 opennlp.tools.ml.model;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.util.StringTokenizer;
import opennlp.tools.util.ObjectStream;
/**
* Class for using a file of {@link Event events} as an {@link ObjectStream event stream}.
* The format of the file is one event per line with
* each line consisting of outcome followed by contexts (space delimited).
*
* @see Event
* @see ObjectStream
*/
public class FileEventStream implements ObjectStream {
private static final String LINE_SEPARATOR = System.lineSeparator();
protected final BufferedReader reader;
/**
* Instantiates a {@link FileEventStream} from the specified file name.
*
* @param fileName The name fo the file containing the events.
* @param encoding The name of the {@link java.nio.charset.Charset character encoding}.
*
* @throws IOException Thrown if the specified file can not be read.
*/
public FileEventStream(String fileName, String encoding) throws IOException {
this(encoding == null ?
new FileReader(fileName) : new InputStreamReader(new FileInputStream(fileName), encoding));
}
/**
* Instantiates a {@link FileEventStream} from the specified file name.
*
* @param fileName The name fo the file containing the events.
*
* @throws IOException Thrown if the specified file can not be read.
*/
public FileEventStream(String fileName) throws IOException {
this(fileName,null);
}
/**
* Instantiates a {@link FileEventStream} via a {@link Reader}.
*
* @param reader The {@link Reader} that holds events.
*
* @throws IOException Thrown if the specified file can not be read.
*/
public FileEventStream(Reader reader) throws IOException {
this.reader = new BufferedReader(reader);
}
/**
* Instantiates a {@link FileEventStream} via a {@link File}.
*
* @param file The {@link File} that holds events.
*
* @throws IOException Thrown if the specified file can not be read.
*/
public FileEventStream(File file) throws IOException {
reader = new BufferedReader(new InputStreamReader(
new FileInputStream(file), StandardCharsets.UTF_8));
}
/**
* Returns the next {@link Event} object. Calling this method repeatedly until it returns
* {@code null} will return each object from the underlying source exactly once.
*
* @return The next object or {@code null} to signal that the stream is exhausted.
*
* @throws IOException Thrown if there is an error during reading.
*/
@Override
public Event read() throws IOException {
String line;
if ((line = reader.readLine()) != null) {
StringTokenizer st = new StringTokenizer(line);
String outcome = st.nextToken();
int count = st.countTokens();
String[] context = new String[count];
for (int ci = 0; ci < count; ci++) {
context[ci] = st.nextToken();
}
return new Event(outcome, context);
}
else {
return null;
}
}
@Override
public void close() throws IOException {
reader.close();
}
/**
* Generates a string representing the specified event.
*
* @param event The {@link Event} for which a string representation is needed.
* @return A string representing the specified event.
*/
public static String toLine(Event event) {
StringBuilder sb = new StringBuilder();
sb.append(event.getOutcome());
String[] context = event.getContext();
for (String s : context) {
sb.append(" ").append(s);
}
sb.append(LINE_SEPARATOR);
return sb.toString();
}
@Override
public void reset() throws IOException, UnsupportedOperationException {
throw new UnsupportedOperationException();
}
}