/*
* 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.juli.logging;
import java.lang.reflect.Constructor;
import java.nio.file.FileSystems;
import java.util.ServiceLoader;
import java.util.logging.LogManager;
import aQute.bnd.annotation.spi.ServiceConsumer;
/**
* This is a modified LogFactory that uses a simple {@link ServiceLoader} based discovery mechanism with a default of
* using JDK based logging. An implementation that uses the full Commons Logging discovery mechanism is available as
* part of the Tomcat extras download.
* <p>
* Why? It is an attempt to strike a balance between simpler code (no discovery) and providing flexibility -
* particularly for those projects that embed Tomcat or some of Tomcat's components - is an alternative logging
* implementation is desired.
* <p>
* Note that this implementation is not just a wrapper around JDK logging (like the original commons-logging impl). It
* adds 2 features - a simpler configuration (which is in fact a subset of log4j.properties) and a formatter that is
* less ugly.
* <p>
* The removal of 'abstract' preserves binary backward compatibility. It is possible to preserve the abstract - and
* introduce another (hardcoded) factory - but I see no benefit.
* <p>
* Since this class is not intended to be extended - all protected methods are removed. This can be changed - but again,
* there is little value in keeping dead code. Just take a quick look at the removed code ( and it's complexity).
* <p>
* Original comment:
* <p>
* Factory for creating {@link Log} instances, with discovery and configuration features similar to that employed by
* standard Java APIs such as JAXP.
* <p>
* <strong>IMPLEMENTATION NOTE</strong> - This implementation is heavily based on the SAXParserFactory and
* DocumentBuilderFactory implementations (corresponding to the JAXP pluggability APIs) found in Apache Xerces.
*/
@ServiceConsumer(value = Log.class)
public class LogFactory {
private static final LogFactory singleton = new LogFactory();
private final Constructor<? extends Log> discoveredLogConstructor;
/**
* Private constructor that is not available for public use.
*/
private LogFactory() {
/*
* Work-around known a JRE bug. https://bugs.openjdk.java.net/browse/JDK-8194653
*
* Preload the default file system. No performance impact as we need to load the default file system anyway.
* Just do it earlier to avoid the potential deadlock.
*
* This can be removed once the oldest JRE supported by Tomcat includes a fix.
*/
FileSystems.getDefault();
// Look via a ServiceLoader for a Log implementation that has a
// constructor taking the String name.
ServiceLoader<Log> logLoader = ServiceLoader.load(Log.class);
Constructor<? extends Log> m = null;
for (Log log : logLoader) {
Class<? extends Log> c = log.getClass();
try {
m = c.getConstructor(String.class);
break;
} catch (NoSuchMethodException | SecurityException e) {
throw new Error(e);
}
}
discoveredLogConstructor = m;
}
// --------------------------------------------------------- Public Methods
// only those 2 methods need to change to use a different direct logger.
/**
* <p>
* Construct (if necessary) and return a <code>Log</code> instance, using the factory's current set of configuration
* attributes.
* </p>
* <p>
* <strong>NOTE</strong> - Depending upon the implementation of the <code>LogFactory</code> you are using, the
* <code>Log</code> instance you are returned may or may not be local to the current application, and may or may not
* be returned again on a subsequent call with the same name argument.
* </p>
*
* @param name Logical name of the <code>Log</code> instance to be returned (the meaning of this name is only known
* to the underlying logging implementation that is being wrapped)
*
* @return A log instance with the requested name
*
* @exception LogConfigurationException if a suitable <code>Log</code> instance cannot be returned
*/
public Log getInstance(String name) throws LogConfigurationException {
if (discoveredLogConstructor == null) {
return DirectJDKLog.getInstance(name);
}
try {
return discoveredLogConstructor.newInstance(name);
} catch (ReflectiveOperationException | IllegalArgumentException e) {
throw new LogConfigurationException(e);
}
}
/**
* Convenience method to derive a name from the specified class and call <code>getInstance(String)</code> with it.
*
* @param clazz Class for which a suitable Log name will be derived
*
* @return A log instance with a name of clazz.getName()
*
* @exception LogConfigurationException if a suitable <code>Log</code> instance cannot be returned
*/
public Log getInstance(Class<?> clazz) throws LogConfigurationException {
return getInstance(clazz.getName());
}
// ------------------------------------------------------- Static Variables
// --------------------------------------------------------- Static Methods
/**
* <p>
* Construct (if necessary) and return a <code>LogFactory</code> instance, using the following ordered lookup
* procedure to determine the name of the implementation class to be loaded.
* </p>
* <ul>
* <li>The <code>org.apache.commons.logging.LogFactory</code> system property.</li>
* <li>The JDK 1.3 Service Discovery mechanism</li>
* <li>Use the properties file <code>commons-logging.properties</code> file, if found in the class path of this
* class. The configuration file is in standard <code>java.util.Properties</code> format and contains the fully
* qualified name of the implementation class with the key being the system property defined above.</li>
* <li>Fall back to a default implementation class
* (<code>org.apache.commons.logging.impl.LogFactoryImpl</code>).</li>
* </ul>
* <p>
* <em>NOTE</em> - If the properties file method of identifying the <code>LogFactory</code> implementation class is
* utilized, all of the properties defined in this file will be set as configuration attributes on the corresponding
* <code>LogFactory</code> instance.
* </p>
*
* @return The singleton LogFactory instance
*
* @exception LogConfigurationException if the implementation class is not available or cannot be instantiated.
*/
public static LogFactory getFactory() throws LogConfigurationException {
return singleton;
}
/**
* Convenience method to return a named logger, without the application having to care about factories.
*
* @param clazz Class from which a log name will be derived
*
* @return A log instance with a name of clazz.getName()
*
* @exception LogConfigurationException if a suitable <code>Log</code> instance cannot be returned
*/
public static Log getLog(Class<?> clazz) throws LogConfigurationException {
return getFactory().getInstance(clazz);
}
/**
* Convenience method to return a named logger, without the application having to care about factories.
*
* @param name Logical name of the <code>Log</code> instance to be returned (the meaning of this name is only known
* to the underlying logging implementation that is being wrapped)
*
* @return A log instance with the requested name
*
* @exception LogConfigurationException if a suitable <code>Log</code> instance cannot be returned
*/
public static Log getLog(String name) throws LogConfigurationException {
return getFactory().getInstance(name);
}
/**
* Release any internal references to previously created {@link LogFactory} instances that have been associated with
* the specified class loader (if any), after calling the instance method <code>release()</code> on each of them.
*
* @param classLoader ClassLoader for which to release the LogFactory
*/
public static void release(ClassLoader classLoader) {
// JULI's log manager looks at the current classLoader so there is no
// need to use the passed in classLoader, the default implementation
// does not so call reset in that case will break things
if (!LogManager.getLogManager().getClass().getName().equals("java.util.logging.LogManager")) {
LogManager.getLogManager().reset();
}
}
}