com.amazonaws.codegen.internal.ClassLoaderHelper Maven / Gradle / Ivy
/*
* Copyright (c) 2016. Amazon.com, Inc. or its affiliates. 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.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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 com.amazonaws.codegen.internal;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
public enum ClassLoaderHelper {
;
/**
* If classesFirst is false, retrieves the resource via the context class loader of the current
* thread, and if not found, via the class loaders of the optionally specified classes in the
* order of their specification, and if not found, from the class loader of
* {@link ClassLoaderHelper} as the last resort.
*
* If classesFirst is true, retrieves the resource via the optionally specified classes in the
* order of their specification, and if not found, via the context class loader of the current
* thread, and if not found, from the class loader of {@link ClassLoaderHelper} as the last
* resort.
*
* @param resource
* resource to be loaded
* @param classesFirst
* true if the class loaders of the optionally specified classes take precedence over
* the context class loader of the current thread; false if the opposite is true.
* @param classes
* class loader providers
* @return the resource loaded as an URL or null if not found.
*/
public static URL getResource(String resource, boolean classesFirst,
Class... classes) {
URL url;
if (classesFirst) {
url = getResourceViaClasses(resource, classes);
if (url == null) {
url = getResourceViaContext(resource);
}
} else {
url = getResourceViaContext(resource);
if (url == null) {
url = getResourceViaClasses(resource, classes);
}
}
return url == null ? ClassLoaderHelper.class.getResource(resource)
: url;
}
private static URL getResourceViaClasses(String resource, Class[] classes) {
if (classes != null) {
for (Class c : classes) {
URL url = c.getResource(resource);
if (url != null)
return url;
}
}
return null;
}
private static URL getResourceViaContext(String resource) {
ClassLoader loader = Thread.currentThread().getContextClassLoader();
return loader == null ? null : loader.getResource(resource);
}
/**
* Retrieves the resource as an input stream via the context class loader of the current thread,
* and if not found, via the class loaders of the optionally specified classes in the order of
* their specification, and if not found, from the class loader of {@link ClassLoaderHelper} as
* the last resort.
*
* @param resource
* resource to be loaded
* @param classes
* class loader providers
* @return the resource loaded as an input stream or null if not found.
*/
public static InputStream getResourceAsStream(String resource,
Class... classes) {
return getResourceAsStream(resource, false, classes);
}
/**
* If classesFirst is false, retrieves the resource as an input stream via the context class
* loader of the current thread, and if not found, via the class loaders of the optionally
* specified classes in the order of their specification, and if not found, from the class
* loader of {@link ClassLoaderHelper} as the last resort.
*
* If classesFirst is true, retrieves the resource as an input stream via the optionally
* specified classes in the order of their specification, and if not found, via the context
* class loader of the current thread, and if not found, from the class loader of
* {@link ClassLoaderHelper} as the last resort.
*
* @param resource
* resource to be loaded
* @param classesFirst
* true if the class loaders of the optionally specified classes take precedence over
* the context class loader of the current thread; false if the opposite is true.
* @param classes
* class loader providers
* @return the resource loaded as an input stream or null if not found.
*/
public static InputStream getResourceAsStream(String resource,
boolean classesFirst, Class... classes) {
URL url = getResource(resource, classesFirst, classes);
try {
return url != null ? url.openStream() : null;
} catch (IOException e) {
return null;
}
}
}