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/*-
* ============LICENSE_START=======================================================
* Copyright (C) 2018 Ericsson. All rights reserved.
* ================================================================================
* Licensed 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.
*
* SPDX-License-Identifier: Apache-2.0
* ============LICENSE_END=========================================================
*/
package org.onap.policy.common.utils.resources;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This is common utility class with static methods for handling Java resources on the class path. It is an abstract
* class to prevent any direct instantiation and private constructor to prevent extending this class.
*/
public abstract class ResourceUtils {
// Get a reference to the logger
private static final Logger LOGGER = LoggerFactory.getLogger(ResourceUtils.class);
// The length of byte buffers used to read resources into strings
private static final int BYTE_BUFFER_LENGH = 1024;
/**
* Private constructor used to prevent sub class instantiation.
*/
private ResourceUtils() {
// Prevent construction of this class
}
/**
* Method to resolve a resource; the local file system is checked first and then the class path is checked.
*
* @param resourceName The resource name
* @return A URL to a resource
*/
public static URL getUrl4Resource(final String resourceName) {
// Check the local fine system first
final URL urlToResource = getLocalFile(resourceName);
// Check if this is a local file
if (urlToResource != null) {
return urlToResource;
} else {
// Resort to the class path
return getUrlResource(resourceName);
}
}
/**
* Method to return a resource as a string. The resource can be on the local file system or in the class path. The
* resource is resolved and loaded into a string.
*
* @param resourceName The resource name
* @return A string containing the resource
*/
public static String getResourceAsString(final String resourceName) {
// Get the resource as a stream, we'll convert it to a string then
final InputStream resourceStream = getResourceAsStream(resourceName);
if (resourceStream == null) {
return null;
}
// Read the stream contents in to an output stream
final ByteArrayOutputStream resourceOutputStreamBuffer = new ByteArrayOutputStream();
final byte[] resourceBuffer = new byte[BYTE_BUFFER_LENGH];
int length;
try {
while ((length = resourceStream.read(resourceBuffer)) != -1) {
resourceOutputStreamBuffer.write(resourceBuffer, 0, length);
}
} catch (final IOException e) {
LOGGER.debug("error reading resource stream \"{}\" : " + e.getMessage(), resourceName, e);
return null;
}
return resourceOutputStreamBuffer.toString();
}
/**
* Method to return a resource as a stream. The resource can be on the local file system or in the class path. The
* resource is resolved and returned as a stream.
*
* @param resourceName The resource name
* @return A stream attached to the resource
*/
public static InputStream getResourceAsStream(final String resourceName) {
// Find a URL to the resource first
final URL urlToResource = getUrl4Resource(resourceName);
// Check if the resource exists
if (urlToResource == null) {
// No resource found
LOGGER.debug("cound not find resource \"{}\" : ", resourceName);
return null;
}
// Read the resource into a string
try {
return urlToResource.openStream();
} catch (final IOException e) {
// Any of many IO exceptions such as the resource is a directory
LOGGER.debug("error attaching resource \"{}\" to stream : " + e.getMessage(), resourceName, e);
return null;
}
}
/**
* Method to get a URL resource from the class path.
*
* @param resourceName The resource name
* @return The URL to the resource
*/
public static URL getUrlResource(final String resourceName) {
try {
final ClassLoader classLoader = ResourceUtils.class.getClassLoader();
final String[] fileParts = resourceName.split("/");
// Read the resource
URL url = classLoader.getResource(resourceName);
// Check if the resource is defined
if (url != null) {
// Return the resource as a file name
LOGGER.debug("found URL resource \"{}\" : ", url);
return url;
} else {
url = classLoader.getResource(fileParts[fileParts.length - 1]);
if (url == null) {
LOGGER.debug("cound not find URL resource \"{}\" : ", resourceName);
return null;
}
LOGGER.debug("found URL resource \"{}\" : ", url);
return url;
}
} catch (final Exception e) {
LOGGER.debug("error getting URL resource \"{}\" : " + e.getMessage(), e);
return null;
}
}
/**
* Method to get a URL resource from the local machine.
*
* @param resourceName The resource name
* @return The URL to the resource
*/
public static URL getLocalFile(final String resourceName) {
try {
// Input might already be in URL format
final URL ret = new URL(resourceName);
final File f = new File(ret.toURI());
if (f.exists()) {
return ret;
}
} catch (final Exception ignore) {
// We ignore exceptions here and catch them below
}
try {
final File f = new File(resourceName);
// Check if the file exists
if (f.exists()) {
final URL urlret = f.toURI().toURL();
LOGGER.debug("resource \"{}\" was found on the local file system", f.toURI().toURL());
return urlret;
} else {
LOGGER.debug("resource \"{}\" does not exist on the local file system", resourceName);
return null;
}
} catch (final Exception e) {
LOGGER.debug("error finding resource \"{}\" : " + e.getMessage(), e);
return null;
}
}
/**
* Gets the file path for a resource on the local file system or on the class path.
*
* @param resource the resource to the get the file path for
* @return the resource file path
*/
public static String getFilePath4Resource(final String resource) {
if (resource == null) {
return null;
}
URL modelFileUrl = getUrl4Resource(resource);
if (modelFileUrl != null) {
return modelFileUrl.getPath();
} else {
return resource;
}
}
}
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