org.apache.hadoop.hdfs.tools.offlineImageViewer.TextWriterImageVisitor 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 org.apache.hadoop.hdfs.tools.offlineImageViewer;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
import com.google.common.base.Charsets;
/**
* TextWriterImageProcessor mixes in the ability for ImageVisitor
* implementations to easily write their output to a text file.
*
* Implementing classes should be sure to call the super methods for the
* constructors, finish and finishAbnormally methods, in order that the
* underlying file may be opened and closed correctly.
*
* Note, this class does not add newlines to text written to file or (if
* enabled) screen. This is the implementing class' responsibility.
*/
abstract class TextWriterImageVisitor extends ImageVisitor {
private boolean printToScreen = false;
private boolean okToWrite = false;
final private OutputStreamWriter fw;
/**
* Create a processor that writes to the file named.
*
* @param filename Name of file to write output to
*/
public TextWriterImageVisitor(String filename) throws IOException {
this(filename, false);
}
/**
* Create a processor that writes to the file named and may or may not
* also output to the screen, as specified.
*
* @param filename Name of file to write output to
* @param printToScreen Mirror output to screen?
*/
public TextWriterImageVisitor(String filename, boolean printToScreen)
throws IOException {
super();
this.printToScreen = printToScreen;
fw = new OutputStreamWriter(Files.newOutputStream(Paths.get(filename)),
Charsets.UTF_8);
okToWrite = true;
}
/* (non-Javadoc)
* @see org.apache.hadoop.hdfs.tools.offlineImageViewer.ImageVisitor#finish()
*/
@Override
void finish() throws IOException {
close();
}
/* (non-Javadoc)
* @see org.apache.hadoop.hdfs.tools.offlineImageViewer.ImageVisitor#finishAbnormally()
*/
@Override
void finishAbnormally() throws IOException {
close();
}
/**
* Close output stream and prevent further writing
*/
private void close() throws IOException {
fw.close();
okToWrite = false;
}
/**
* Write parameter to output file (and possibly screen).
*
* @param toWrite Text to write to file
*/
protected void write(String toWrite) throws IOException {
if(!okToWrite)
throw new IOException("file not open for writing.");
if(printToScreen)
System.out.print(toWrite);
try {
fw.write(toWrite);
} catch (IOException e) {
okToWrite = false;
throw e;
}
}
}