org.apache.juli.logging.LogFactory Maven / Gradle / Ivy
/*
* 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.util.Properties;
import java.util.ServiceLoader;
import org.ops4j.pax.logging.PaxLogger;
import org.ops4j.pax.logging.PaxLoggingManager;
import org.ops4j.pax.logging.internal.Activator;
import org.ops4j.pax.logging.juli.JuliLogger;
import org.ops4j.pax.logging.spi.support.FallbackLogFactory;
import org.osgi.framework.FrameworkUtil;
/**
* 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.
*
* 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.
*
* 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.
*
* 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.
*
* 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).
*
* --------------
*
* Original comment:
* Factory for creating {@link Log} instances, with discovery and
* configuration features similar to that employed by standard Java APIs
* such as JAXP.
*
* IMPLEMENTATION NOTE - This implementation is heavily
* based on the SAXParserFactory and DocumentBuilderFactory implementations
* (corresponding to the JAXP pluggability APIs) found in Apache Xerces.
*
* pax-logging-api used source from org.apache.tomcat:juli:6.0.53 but ensures that it's API
* compatible with 9.0.x
*
* @author Niclas Hedhman (responsible for the OSGi adaptation.)
* @author Craig R. McClanahan
* @author Costin Manolache
* @author Richard A. Sitze
* @author Grzegorz Grzybek (adjustments and code cleanup)
*/
public /* abstract */ class LogFactory {
private static PaxLoggingManager m_paxLogging;
public static void setPaxLoggingManager(PaxLoggingManager manager) {
m_paxLogging = manager;
}
// ----------------------------------------------------- Manifest Constants
/**
* The name of the property used to identify the LogFactory implementation
* class name.
*/
public static final String FACTORY_PROPERTY =
"org.apache.commons.logging.LogFactory";
/**
* The fully qualified class name of the fallback LogFactory
* implementation class to use, if no other can be found.
*/
public static final String FACTORY_DEFAULT =
"org.apache.commons.logging.impl.LogFactoryImpl";
/**
* The name of the properties file to search for.
*/
public static final String FACTORY_PROPERTIES =
"commons-logging.properties";
/**
* Setting this system property value allows the Hashtable used to store
* classloaders to be substituted by an alternative implementation.
*
* Note: LogFactory will print:
*
*
* [ERROR] LogFactory: Load of custom hashtable failed
*
* to system error and then continue using a standard Hashtable.
*
* Usage: Set this property when Java is invoked
* and LogFactory will attempt to load a new instance
* of the given implementation class.
* For example, running the following ant scriplet:
*
*
* <java classname="${test.runner}" fork="yes" failonerror="${test.failonerror}">
* ...
* <sysproperty
* key="org.apache.commons.logging.LogFactory.HashtableImpl"
* value="org.apache.commons.logging.AltHashtable"/>
* </java>
*
*
* will mean that LogFactory will load an instance of
* org.apache.commons.logging.AltHashtable.
*
* A typical use case is to allow a custom
* Hashtable implementation using weak references to be substituted.
* This will allow classloaders to be garbage collected without
* the need to release them (on 1.3+ JVMs only, of course ;)
*/
public static final String HASHTABLE_IMPLEMENTATION_PROPERTY =
"org.apache.commons.logging.LogFactory.HashtableImpl";
private static final LogFactory singleton = new LogFactory();
// ----------------------------------------------------------- Constructors
/**
* Protected constructor that is not available for public use.
*/
private LogFactory() {
}
// hook for syserr logger - class level
void setLogConfig( Properties p ) {
}
// --------------------------------------------------------- Public Methods
// only those 2 methods need to change to use a different direct logger.
/**
*
Construct (if necessary) and return a Log instance,
* using the factory's current set of configuration attributes.
*
* NOTE - Depending upon the implementation of
* the LogFactory you are using, the Log
* 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.
*
* @param name Logical name of the Log 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 Log
* instance cannot be returned
*/
public Log getInstance(String name) throws LogConfigurationException {
PaxLogger logger;
if (m_paxLogging == null) {
logger = FallbackLogFactory.createFallbackLog(FrameworkUtil.getBundle(Log.class), name);
} else {
logger = m_paxLogging.getLogger(name, JuliLogger.JULI_FQCN);
}
JuliLogger juliLogger = new JuliLogger(name, logger);
if (m_paxLogging == null) {
synchronized (Activator.m_loggers) {
Activator.m_loggers.add(juliLogger);
}
}
return juliLogger;
}
/**
* Release any internal references to previously created {@link Log}
* instances returned by this factory. This is useful in environments
* like servlet containers, which implement application reloading by
* throwing away a ClassLoader. Dangling references to objects in that
* class loader would prevent garbage collection.
*/
public void release() {
}
/**
* Return the configuration attribute with the specified name (if any),
* or null if there is no such attribute.
*
* @param name Name of the attribute to return
*/
public Object getAttribute(String name) {
return null;
}
/**
* Return an array containing the names of all currently defined
* configuration attributes. If there are no such attributes, a zero
* length array is returned.
*/
public String[] getAttributeNames() {
return new String[0];
}
/**
* Remove any configuration attribute associated with the specified name.
* If there is no such attribute, no action is taken.
*
* @param name Name of the attribute to remove
*/
public void removeAttribute(String name) {
}
/**
* Set the configuration attribute with the specified name. Calling
* this with a null value is equivalent to calling
* removeAttribute(name).
*
* @param name Name of the attribute to set
* @param value Value of the attribute to set, or null
* to remove any setting for this attribute
*/
public void setAttribute(String name, Object value) {
}
/**
* Convenience method to derive a name from the specified class and
* call getInstance(String) 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 Log
* instance cannot be returned
*/
public Log getInstance(Class clazz) throws LogConfigurationException {
return getInstance( clazz.getName());
}
// ------------------------------------------------------- Static Variables
// --------------------------------------------------------- Static Methods
/**
* Construct (if necessary) and return a LogFactory
* instance, using the following ordered lookup procedure to determine
* the name of the implementation class to be loaded.
*
* - The
org.apache.commons.logging.LogFactory system
* property.
* - The JDK 1.3 Service Discovery mechanism
* - Use the properties file
commons-logging.properties
* file, if found in the class path of this class. The configuration
* file is in standard java.util.Properties format and
* contains the fully qualified name of the implementation class
* with the key being the system property defined above.
* - Fall back to a default implementation class
* (
org.apache.commons.logging.impl.LogFactoryImpl).
*
*
* NOTE - If the properties file method of identifying the
* LogFactory implementation class is utilized, all of the
* properties defined in this file will be set as configuration attributes
* on the corresponding LogFactory instance.
*
* @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 Log
* 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 Log 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 Log
* 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 release() on
* each of them.
*
* @param classLoader ClassLoader for which to release the LogFactory
*/
public static void release(ClassLoader classLoader) {
}
/**
* Release any internal references to previously created {@link LogFactory}
* instances, after calling the instance method release() on
* each of them. This is useful in environments like servlet containers,
* which implement application reloading by throwing away a ClassLoader.
* Dangling references to objects in that class loader would prevent
* garbage collection.
*/
public static void releaseAll() {
}
/**
* Returns a string that uniquely identifies the specified object, including
* its class.
*
* The returned string is of form "classname@hashcode", ie is the same as
* the return value of the Object.toString() method, but works even when
* the specified object's class has overidden the toString method.
*
* @param o may be null.
* @return a string of form classname@hashcode, or "null" if param o is null.
*/
public static String objectId(Object o) {
if (o == null) {
return "null";
} else {
return o.getClass().getName() + "@" + System.identityHashCode(o);
}
}
}