/*
* Copyright 2013 the original author or authors.
*
* 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 org.springframework.xd.batch.item.hadoop;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.List;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.springframework.batch.item.WriteFailedException;
import org.springframework.batch.item.file.transform.LineAggregator;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;
/**
*
* @author Mark Pollack
*/
public class HdfsTextItemWriter<T> extends AbstractHdfsItemWriter<T> implements InitializingBean {
private static final String DEFAULT_LINE_SEPARATOR = System.getProperty("line.separator");
private FileSystem fileSystem;
private FSDataOutputStream fsDataOutputStream;
private LineAggregator<T> lineAggregator;
private String lineSeparator = DEFAULT_LINE_SEPARATOR;
private volatile String charset = "UTF-8";
public HdfsTextItemWriter(FileSystem fileSystem) {
Assert.notNull(fileSystem, "Hadoop FileSystem must not be null.");
this.fileSystem = fileSystem;
}
@Override
public void write(List<? extends T> items) throws Exception {
initializeCounterIfNecessary();
prepareOutputStream();
copy(getItemsAsBytes(items), this.fsDataOutputStream);
}
private void prepareOutputStream() throws IOException {
boolean found = false;
Path name = null;
// TODO improve algorithm
while (!found) {
name = new Path(getFileName());
// If it doesn't exist, create it. If it exists, return false
if (getFileSystem().createNewFile(name)) {
logger.debug("Created new HDFS file " + name.getName());
found = true;
this.resetBytesWritten();
this.fsDataOutputStream = this.getFileSystem().append(name);
}
else {
if (this.getBytesWritten() >= getRolloverThresholdInBytes()) {
logger.debug("Rolling over new file");
closeStream();
incrementCounter();
}
else {
found = true;
}
}
}
}
/**
* Simple not optimized copy
*/
private void copy(byte[] in, FSDataOutputStream out) throws IOException {
out.write(in);
incrementBytesWritten(in.length);
}
@Override
public FileSystem getFileSystem() {
return this.fileSystem;
}
/**
* Converts the list of items to a byte array.
*
* @param items
* @return the byte array
*/
private byte[] getItemsAsBytes(List<? extends T> items) {
StringBuilder lines = new StringBuilder();
for (T item : items) {
lines.append(lineAggregator.aggregate(item) + lineSeparator);
}
try {
return lines.toString().getBytes(this.charset);
}
catch (UnsupportedEncodingException e) {
throw new WriteFailedException("Could not write data.", e);
}
}
@Override
public void close() {
logger.debug("Closing item writer");
closeStream();
reset();
}
private void closeStream() {
logger.debug("Closing output stream");
if (fsDataOutputStream != null) {
IOUtils.closeStream(fsDataOutputStream);
}
}
/**
* Public setter for the {@link LineAggregator}. This will be used to translate the item into a line for output.
*
* @param lineAggregator the {@link LineAggregator} to set
*/
public void setLineAggregator(LineAggregator<T> lineAggregator) {
this.lineAggregator = lineAggregator;
}
@Override
public void afterPropertiesSet() throws Exception {
Assert.notNull(lineAggregator, "A LineAggregator must be provided.");
}
}