org.apache.hadoop.util.DiskValidatorFactory 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.util;
import org.apache.hadoop.thirdparty.com.google.common.annotations.VisibleForTesting;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.util.DiskChecker.DiskErrorException;
import java.util.concurrent.ConcurrentHashMap;
/**
* The factory class to create instance of {@link DiskValidator}.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public final class DiskValidatorFactory {
@VisibleForTesting
static final ConcurrentHashMap, DiskValidator>
INSTANCES = new ConcurrentHashMap<>();
private DiskValidatorFactory() {
}
/**
* Returns a {@link DiskValidator} instance corresponding to the passed clazz.
* @param clazz a class extends {@link DiskValidator}
*/
public static DiskValidator
getInstance(Class clazz) {
DiskValidator diskValidator;
if (INSTANCES.containsKey(clazz)) {
diskValidator = INSTANCES.get(clazz);
} else {
diskValidator = ReflectionUtils.newInstance(clazz, null);
// check the return of putIfAbsent() to see if any other thread have put
// the instance with the same key into INSTANCES
DiskValidator diskValidatorRet =
INSTANCES.putIfAbsent(clazz, diskValidator);
if (diskValidatorRet != null) {
diskValidator = diskValidatorRet;
}
}
return diskValidator;
}
/**
* Returns {@link DiskValidator} instance corresponding to its name.
* The diskValidator parameter can be "basic" for {@link BasicDiskValidator}
* or "read-write" for {@link ReadWriteDiskValidator}.
* @param diskValidator canonical class name, for example, "basic"
* @throws DiskErrorException if the class cannot be located
*/
@SuppressWarnings("unchecked")
public static DiskValidator getInstance(String diskValidator)
throws DiskErrorException {
@SuppressWarnings("rawtypes")
Class clazz;
if (diskValidator.equalsIgnoreCase(BasicDiskValidator.NAME)) {
clazz = BasicDiskValidator.class;
} else if (diskValidator.equalsIgnoreCase(ReadWriteDiskValidator.NAME)) {
clazz = ReadWriteDiskValidator.class;
} else {
try {
clazz = Class.forName(diskValidator);
} catch (ClassNotFoundException cnfe) {
throw new DiskErrorException(diskValidator
+ " DiskValidator class not found.", cnfe);
}
}
return getInstance(clazz);
}
}