org.apache.lucene.analysis.util.FilesystemResourceLoader 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.lucene.analysis.util;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
/**
* Simple {@link ResourceLoader} that opens resource files
* from the local file system, optionally resolving against
* a base directory.
*
* This loader wraps a delegate {@link ResourceLoader}
* that is used to resolve all files, the current base directory
* does not contain. {@link #newInstance} is always resolved
* against the delegate, as a {@link ClassLoader} is needed.
*
*
You can chain several {@code FilesystemResourceLoader}s
* to allow lookup of files in more than one base directory.
*/
public final class FilesystemResourceLoader implements ResourceLoader {
private final Path baseDirectory;
private final ResourceLoader delegate;
/**
* Creates a resource loader that resolves resources against the given
* base directory (may be {@code null} to refer to CWD).
* Files not found in file system and class lookups are delegated to context
* classloader.
*
* @deprecated You should not use this ctor, because it uses the thread's context
* class loader as fallback for resource lookups, which is bad programming style.
* Please specify a {@link ClassLoader} instead.
* @see #FilesystemResourceLoader(Path, ClassLoader)
*/
@Deprecated
public FilesystemResourceLoader(Path baseDirectory) {
this(baseDirectory, new ClasspathResourceLoader());
}
/**
* Creates a resource loader that resolves resources against the given
* base directory (may be {@code null} to refer to CWD).
* Files not found in file system and class lookups are delegated to context
* classloader.
*/
public FilesystemResourceLoader(Path baseDirectory, ClassLoader delegate) {
this(baseDirectory, new ClasspathResourceLoader(delegate));
}
/**
* Creates a resource loader that resolves resources against the given
* base directory (may be {@code null} to refer to CWD).
* Files not found in file system and class lookups are delegated
* to the given delegate {@link ResourceLoader}.
*/
public FilesystemResourceLoader(Path baseDirectory, ResourceLoader delegate) {
if (baseDirectory == null) {
throw new NullPointerException();
}
if (!Files.isDirectory(baseDirectory))
throw new IllegalArgumentException(baseDirectory + " is not a directory");
if (delegate == null)
throw new IllegalArgumentException("delegate ResourceLoader may not be null");
this.baseDirectory = baseDirectory;
this.delegate = delegate;
}
@Override
public InputStream openResource(String resource) throws IOException {
try {
return Files.newInputStream(baseDirectory.resolve(resource));
} catch (FileNotFoundException | NoSuchFileException fnfe) {
return delegate.openResource(resource);
}
}
@Override
public T newInstance(String cname, Class expectedType) {
return delegate.newInstance(cname, expectedType);
}
@Override
public Class findClass(String cname, Class expectedType) {
return delegate.findClass(cname, expectedType);
}
}