/*
* 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.logging.log4j.util;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Properties;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.spi.Provider;
import org.apache.logging.log4j.status.StatusLogger;
/**
* <em>Consider this class private.</em>
*/
public final class ProviderUtil {
private static final String PROVIDER_RESOURCE = "META-INF/log4j-provider.properties";
private static final String API_VERSION = "Log4jAPIVersion";
private static final String[] COMPATIBLE_API_VERSIONS = {
"2.0.0"
};
private static final Logger LOGGER = StatusLogger.getLogger();
private static final Collection<Provider> PROVIDERS = new ArrayList<Provider>();
private ProviderUtil() {
}
static {
final ClassLoader cl = findClassLoader();
Enumeration<URL> enumResources = null;
try {
enumResources = cl.getResources(PROVIDER_RESOURCE);
} catch (final IOException e) {
LOGGER.fatal("Unable to locate {}", PROVIDER_RESOURCE, e);
}
loadProviders(enumResources);
}
protected static void loadProviders(final Enumeration<URL> enumResources) {
if (enumResources != null) {
while (enumResources.hasMoreElements()) {
final URL url = enumResources.nextElement();
try {
final Properties props = PropertiesUtil.loadClose(url.openStream(), url);
if (!validVersion(props.getProperty(API_VERSION))) {
continue;
}
PROVIDERS.add(new Provider(props, url));
} catch (final IOException ioe) {
LOGGER.error("Unable to open {}", url, ioe);
}
}
}
}
public static Iterable<Provider> getProviders() {
return PROVIDERS;
}
public static boolean hasProviders() {
return !PROVIDERS.isEmpty();
}
public static ClassLoader findClassLoader() {
ClassLoader cl;
if (System.getSecurityManager() == null) {
cl = Thread.currentThread().getContextClassLoader();
} else {
cl = java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<ClassLoader>() {
@Override
public ClassLoader run() {
return Thread.currentThread().getContextClassLoader();
}
}
);
}
if (cl == null) {
cl = ProviderUtil.class.getClassLoader();
}
return cl;
}
private static boolean validVersion(final String version) {
for (final String v : COMPATIBLE_API_VERSIONS) {
if (version.startsWith(v)) {
return true;
}
}
return false;
}
}