001/*
002 * Copyright 2023 the original author or authors.
003 * <p>
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 * <p>
008 * https://www.apache.org/licenses/LICENSE-2.0
009 * <p>
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package de.cuioss.tools.io;
017
018import java.io.IOException;
019import java.io.InputStream;
020import java.io.Serializable;
021import java.net.URL;
022
023/**
024 * Wraps different ways file loading: FileSystem (absolute), Classpath,..
025 * <p>
026 * The implementations must be reentrant regarding {@link #inputStream()}
027 * </p>
028 *
029 * @author Oliver Wolff
030 */
031public interface FileLoader extends Serializable {
032
033    /**
034     * @return boolean indicating whether the concrete file exists and is accessible
035     */
036    boolean isReadable();
037
038    /**
039     * @return the filename in an appropriate presentation.
040     */
041    StructuredFilename getFileName();
042
043    /**
044     * This method should be within a {@code try-with-resources} statement as it is
045     * not closed by the implementation.
046     *
047     * @return an {@link InputStream} on the corresponding file. It implicitly
048     *         checks {@link #isReadable()} before accessing the file and will throw
049     *         an {@link IllegalStateException} in case it is not readable.
050     * @throws IOException
051     */
052    InputStream inputStream() throws IOException;
053
054    /**
055     * @return an {@link URL} on the corresponding file.
056     */
057    URL getURL();
058
059    /**
060     * @return boolean indicating that the loader loads from the file-system and not
061     *         from the classpath
062     */
063    boolean isFilesystemLoader();
064}