1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.configuration2.io; 18 19 import java.net.URL; 20 21 /** 22 * <p> 23 * An interface allowing applications to customize the process of locating a file. 24 * </p> 25 * <p> 26 * {@link FileHandler} uses {@link FileLocator} objects for referencing files. These objects are not guaranteed to 27 * identify a file in a unique way. For instance, if only a file name is defined, this could mean a relative file name 28 * in the current directory, the name of a resource to be loaded from the class path, or something else. Before the file 29 * described by a {@code FileLocator} can be actually accessed, an unambiguous URL pointing to this file has to be 30 * obtained. This is the job of a {@code FileLocationStrategy}. 31 * </p> 32 * <p> 33 * This interface defines a method for locating a file provided as a {@code FileLocator} object. If location is 34 * successful, a URL is returned. A concrete implementation can perform arbitrary actions to search for the file in 35 * question at various places. There will also be an implementation allowing the combination of multiple 36 * {@code FileLocationStrategy} implementations; so a file can be searched using multiple strategies until one of them 37 * is successful. 38 * </p> 39 * 40 * @since 2.0 41 */ 42 public interface FileLocationStrategy { 43 /** 44 * Tries to locate the specified file. The method also expects the {@code FileSystem} to be used. Note that the 45 * {@code FileLocator} object may also contain a {@code FileSystem}, but this is optional. The passed in 46 * {@code FileSystem} should be used, and callers must not pass a <b>null</b> reference for this argument. A concrete 47 * implementation has to evaluate the properties stored in the {@code FileLocator} object and try to match them to an 48 * existing file. If this can be done, a corresponding URL is returned. Otherwise, result is <b>null</b>. 49 * Implementations should not throw an exception (unless parameters are <b>null</b>) as there might be alternative 50 * strategies which can find the file in question. 51 * 52 * @param fileSystem the {@code FileSystem} to be used for this operation 53 * @param locator the object describing the file to be located 54 * @return a URL pointing to the referenced file if location was successful; <b>null</b> if the file could not be 55 * resolved 56 */ 57 URL locate(FileSystem fileSystem, FileLocator locator); 58 }