org.apache.hadoop.fs.HadoopFsWrapper 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 /*CHECKSTYLE.OFF: PackageName*/org.apache.hadoop.fs/*CHECKSTYLE.ON: PackageName*/;
import org.apache.druid.java.util.common.logger.Logger;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* This wrapper class is created to be able to access some of the the "protected" methods inside Hadoop's
* FileSystem class. Those are supposed to become public eventually or more appropriate alternatives would be
* provided.
* This is a hack and should be removed when no longer necessary.
*/
public class HadoopFsWrapper
{
private static final Logger log = new Logger(HadoopFsWrapper.class);
private HadoopFsWrapper()
{
}
/**
* Same as FileSystem.rename(from, to, Options.Rename). It is different from FileSystem.rename(from, to) which moves
* "from" directory inside "to" directory if it already exists.
*
* @param from
* @param to
*
* @return true if operation succeeded, false if destination already exists
*
* @throws IOException if trying to overwrite a non-empty directory
*/
public static boolean rename(FileSystem fs, Path from, Path to)
{
try {
// Note: Using reflection instead of simpler
// fs.rename(from, to, Options.Rename.NONE);
// due to the issues discussed in https://github.com/apache/incubator-druid/pull/3787
Method renameMethod = findRenameMethodRecursively(fs.getClass());
renameMethod.invoke(fs, from, to, new Options.Rename[]{Options.Rename.NONE});
return true;
}
catch (InvocationTargetException ex) {
if (ex.getTargetException() instanceof FileAlreadyExistsException) {
log.info(ex, "Destination exists while renaming [%s] to [%s]", from, to);
return false;
} else {
throw new RuntimeException(ex);
}
}
catch (NoSuchMethodException | IllegalAccessException ex) {
for (Method method : fs.getClass().getDeclaredMethods()) {
log.error(method.toGenericString());
}
throw new RuntimeException(ex);
}
}
/**
* Finds "rename" method recursively through the FileSystem class hierarchy. This is required because
* clazz.getMethod(..) only returns PUBLIC methods in clazz hierarchy.
* and clazz.getDeclaredMethod(..) only returns all methods declared in clazz but not inherited ones.
*/
private static Method findRenameMethodRecursively(Class clazz) throws NoSuchMethodException
{
try {
Method renameMethod = clazz.getDeclaredMethod("rename", Path.class, Path.class, Options.Rename[].class);
renameMethod.setAccessible(true);
return renameMethod;
}
catch (NoSuchMethodException ex) {
Class superClazz = clazz.getSuperclass();
if (superClazz == null) {
throw ex;
} else {
return findRenameMethodRecursively(superClazz);
}
}
}
}