src/main/java/org/apache/directory/fortress/core/util/ResourceUtil.java

/*
 *   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.directory.fortress.core.util;

import java.io.*;
import java.net.URL;

/**
 * Getting a resource.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public final class ResourceUtil {
    /**
     * Private constructor
     */
    private ResourceUtil() {
    }


    /**
     * Checks that the reference is either an absolute path to a file, or a reference to a file within reach of class loader resources.
     * A directory is not accepted.
     * @param _reference
     * @return An InputStream to a file, or null if no file was found.
     */
    public static InputStream getInputStream(String _reference) {
        InputStream result = null;
        if (null != _reference) {
            result = getInputStreamForFileAbsolutePath(_reference);
            if (null == result) {
                // When getting here, it's not a file and not a directory, but it might still translate into a directory within resources
                result = getInputStreamForFileInClassLoaderResources(_reference);
            }
        }
        return result;
    }

    /**
     * Will check that the path is absolute and is pointing to an existing file.
     * A directory is not accepted.
     * @param _path absolute path to a file
     * @return An InputStream if the path is absolute and is pointing to a file, or null if no file was found.
     */
    public static InputStream getInputStreamForFileAbsolutePath(String _path) {
        InputStream result = null;
        if (null != _path) {
            File file = new File(_path);
            if (file.exists() && file.isAbsolute() && !file.isDirectory()) {
                try {
                    result = new FileInputStream(file);
                } catch (FileNotFoundException e) {
                    // Don't care
                }
            }
        }
        return result;
    }

    /**
     * Will check that the reference is a file, eventually within another jar.
     * A directory is not accepted.
     * @param _reference the relative path of a file to find within class loader resources.
     * @return An InputStream if the reference resolves to a file within the reach of class loader resources, or null if no file was found.
     */
    private static InputStream getInputStreamForFileInClassLoaderResources(String _reference) {
        InputStream result = null;
        URL url = ResourceUtil.class.getClassLoader().getResource(_reference);
        if (null != url) {
            if (url.getProtocol().equals("file")) {
                File file = new File(url.getPath());
                if (file.exists()) {
                    if (!file.isDirectory()) {
                        try {
                            result = new FileInputStream(file);
                        } catch (FileNotFoundException e) {
                            // Don't care
                        }
                    }
                }
            } else if (url.getProtocol().equals("jar")){
                result = ResourceUtil.class.getClassLoader().getResourceAsStream(_reference);
                if (null != result) {
                    PushbackInputStream pushbackInputStream = new PushbackInputStream(result);
                    int b = -1;
                    try {
                        b = pushbackInputStream.read();
                    } catch (IOException e) {
                        // Don't care
                    }
                    if (b != -1) {
                        result = pushbackInputStream;
                        try {
                            pushbackInputStream.unread(b);
                        } catch (IOException e) {
                            result = null;
                        }
                    }
                }
            }
        }
        return result;
    }
}