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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.commons.configuration2.io;
import java.net.URL;
/**
*
* An interface allowing applications to customize the process of locating a
* file.
*
*
* {@link FileHandler} uses {@link FileLocator} objects for referencing files.
* These objects are not guaranteed to identify a file in a unique way. For
* instance, if only a file name is defined, this could mean a relative file
* name in the current directory, the name of a resource to be loaded from the
* class path, or something else. Before the file described by a
* {@code FileLocator} can be actually accessed, an unambiguous URL pointing to
* this file has to be obtained. This is the job of a
* {@code FileLocationStrategy}.
*
*
* This interface defines a method for locating a file provided as a
* {@code FileLocator} object. If location is successful, a URL is returned. A
* concrete implementation can perform arbitrary actions to search for the file
* in question at various places. There will also be an implementation allowing
* the combination of multiple {@code FileLocationStrategy} implementations; so
* a file can be searched using multiple strategies until one of them is
* successful.
*
*
* @since 2.0
*/
public interface FileLocationStrategy
{
/**
* Tries to locate the specified file. The method also expects the
* {@code FileSystem} to be used. Note that the {@code FileLocator} object
* may also contain a {@code FileSystem}, but this is optional. The passed
* in {@code FileSystem} should be used, and callers must not pass a
* null reference for this argument. A concrete implementation has to
* evaluate the properties stored in the {@code FileLocator} object and try
* to match them to an existing file. If this can be done, a corresponding
* URL is returned. Otherwise, result is null. Implementations should
* not throw an exception (unless parameters are null) as there might
* be alternative strategies which can find the file in question.
*
* @param fileSystem the {@code FileSystem} to be used for this operation
* @param locator the object describing the file to be located
* @return a URL pointing to the referenced file if location was successful;
* null if the file could not be resolved
*/
URL locate(FileSystem fileSystem, FileLocator locator);
}