org.apache.hadoop.fs.impl.FsLinkResolution Maven / Gradle / Ivy
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* 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.fs.impl;
import java.io.IOException;
import org.apache.hadoop.thirdparty.com.google.common.base.Preconditions;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.AbstractFileSystem;
import org.apache.hadoop.fs.FSLinkResolver;
import org.apache.hadoop.fs.FileContext;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.UnresolvedLinkException;
/**
* Class to allow Lambda expressions to be used in {@link FileContext}
* link resolution.
* @param type of the returned value.
*/
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class FsLinkResolution extends FSLinkResolver {
/**
* The function to invoke in the {@link #next(AbstractFileSystem, Path)} call.
*/
private final FsLinkResolutionFunction fn;
/**
* Construct an instance with the given function.
* @param fn function to invoke.
*/
public FsLinkResolution(final FsLinkResolutionFunction fn) {
this.fn = Preconditions.checkNotNull(fn);
}
@Override
public T next(final AbstractFileSystem fs, final Path p)
throws UnresolvedLinkException, IOException {
return fn.apply(fs, p);
}
/**
* The signature of the function to invoke.
* @param type resolved to
*/
@FunctionalInterface
public interface FsLinkResolutionFunction {
/**
*
* @param fs filesystem to resolve against.
* @param path path to resolve
* @return a result of type T
* @throws UnresolvedLinkException link resolution failure
* @throws IOException other IO failure.
*/
T apply(final AbstractFileSystem fs, final Path path)
throws IOException, UnresolvedLinkException;
}
/**
* Apply the given function to the resolved path under the the supplied
* FileContext.
* @param fileContext file context to resolve under
* @param path path to resolve
* @param fn function to invoke
* @param return type.
* @return the return value of the function as revoked against the resolved
* path.
* @throws UnresolvedLinkException link resolution failure
* @throws IOException other IO failure.
*/
public static T resolve(
final FileContext fileContext, final Path path,
final FsLinkResolutionFunction fn)
throws UnresolvedLinkException, IOException {
return new FsLinkResolution<>(fn).resolve(fileContext, path);
}
}