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author | 2018-08-01 13:16:04 +0000 | |
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committer | 2018-08-01 13:16:04 +0000 | |
commit | 6d662cb19aa858b743ab7e01d02a2a173abebcad (patch) | |
tree | 0852bf20d6bc9c16012f9c284c84b8a990f32e02 /utils/src/main | |
parent | 59c650d413522286a047f470e59a1142d9eb20b2 (diff) | |
parent | 1b6404f2ab7fe93ecc0c7e4c91bc90c7aa94b42f (diff) |
Merge "Add resource handling utility class"
Diffstat (limited to 'utils/src/main')
-rw-r--r-- | utils/src/main/java/org/onap/policy/common/utils/resources/ResourceUtils.java | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/utils/src/main/java/org/onap/policy/common/utils/resources/ResourceUtils.java b/utils/src/main/java/org/onap/policy/common/utils/resources/ResourceUtils.java new file mode 100644 index 00000000..cca6e626 --- /dev/null +++ b/utils/src/main/java/org/onap/policy/common/utils/resources/ResourceUtils.java @@ -0,0 +1,214 @@ +/*- + * ============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; + } + } +} |