org.apache.commons.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.
*/
/*
* NOTE!!!! This is NOT the original Jakarta Commons Logging, but an adaption
* of its interface so that this Log4J OSGi bundle can export the JCL interface
* but redirect to dynamically configured logging library.
* There is nothing here that is useful outside an OSGi environment.
*/
package org.apache.commons.logging;
import java.util.Hashtable;
import org.ops4j.pax.logging.PaxLogger;
import org.ops4j.pax.logging.PaxLoggingManager;
import org.ops4j.pax.logging.internal.Activator;
import org.ops4j.pax.logging.jcl.JclLogger;
import org.ops4j.pax.logging.spi.support.FallbackLogFactory;
import org.osgi.framework.FrameworkUtil;
/**
* This is an adaptation of the Jakarta Commons Logging API for OSGi usage.
*
*
This is the only class from {@code org.apache.commons.logging} package that is adjusted. Other
* commons-logging classes are simply repackaged from original jar.
*
*
There's no need for discovery code that's constituting most of original version's functionality.
*
*
Original {@code org.apache.commons.logging.LogFactory} is abstract. In pax-logging-api,
* this class is concrete. All public methods and fields are preserved. Unnecessary private and protected methods
* and fields are removed.
*
*
pax-logging-api used source from commons-logging:commons-logging:1.2
*
* @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 class LogFactory {
private static PaxLoggingManager m_paxLogging;
public static void setPaxLoggingManager(PaxLoggingManager manager) {
m_paxLogging = manager;
}
// copy of original, public constants, to preserve the API
// ----------------------------------------------------- Manifest Constants
/**
* The name (priority) of the key in the config file used to
* specify the priority of that particular config file. The associated value
* is a floating-point number; higher values take priority over lower values.
*/
public static final String PRIORITY_KEY = "priority";
/**
* The name (use_tccl) of the key in the config file used
* to specify whether logging classes should be loaded via the thread
* context class loader (TCCL), or not. By default, the TCCL is used.
*/
public static final String TCCL_KEY = "use_tccl";
/**
* The name (org.apache.commons.logging.LogFactory) of the property
* used to identify the LogFactory implementation
* class name. This can be used as a system property, or as an entry in a
* configuration properties file.
*/
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.LogFactory";
/**
* The name (commons-logging.properties) of the properties file to search for.
*/
public static final String FACTORY_PROPERTIES = "commons-logging.properties";
/**
* JDK1.3+
* 'Service Provider' specification.
*/
protected static final String SERVICE_ID =
"META-INF/services/org.apache.commons.logging.LogFactory";
/**
* The name (org.apache.commons.logging.diagnostics.dest)
* of the property used to enable internal commons-logging
* diagnostic output, in order to get information on what logging
* implementations are being discovered, what classloaders they
* are loaded through, etc.
*
* If a system property of this name is set then the value is
* assumed to be the name of a file. The special strings
* STDOUT or STDERR (case-sensitive) indicate output to
* System.out and System.err respectively.
*
* Diagnostic logging should be used only to debug problematic
* configurations and should not be set in normal production use.
*/
public static final String DIAGNOSTICS_DEST_PROPERTY =
"org.apache.commons.logging.diagnostics.dest";
/**
* Setting this system property
* (org.apache.commons.logging.LogFactory.HashtableImpl)
* 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";
/**
* Singleton instance without discovery
*/
private static final LogFactory m_instance = new LogFactory();
// ----------------------------------------------------------- Constructors
/**
* Protected constructor that is not available for public use.
*/
protected LogFactory() {
}
// --------------------------------------------------------- Public Methods
/**
* 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];
}
/**
* 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
* @throws LogConfigurationException if a suitable Log
* instance cannot be returned
*/
public Log getInstance(Class clazz)
throws LogConfigurationException {
return getInstance(clazz.getName());
}
/**
* 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.
*
* In pax-logging, loggers are obtained from current or fallback
* {@link PaxLoggingManager}
*
* @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)
* @throws 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, JclLogger.JCL_FQCN);
}
JclLogger jclLogger = new JclLogger(name, logger);
if (m_paxLogging == null) {
synchronized (Activator.m_loggers) {
Activator.m_loggers.add(jclLogger);
}
}
return jclLogger;
}
/**
* 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() {
}
/**
* 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) {
}
// ------------------------------------------------------- Static Variables
/**
* The previously constructed LogFactory instances, keyed by
* the ClassLoader with which it was created.
*/
protected static Hashtable factories = null;
/**
* Previously constructed LogFactory instance as in the
* factories map, but for the case where
* getClassLoader returns null.
* This can happen when:
*
* - using JDK1.1 and the calling code is loaded via the system
* classloader (very common)
* - using JDK1.2+ and the calling code is loaded via the boot
* classloader (only likely for embedded systems work).
*
* Note that factories is a Hashtable (not a HashMap),
* and hashtables don't allow null as a key.
* @deprecated since 1.1.2
*/
protected static volatile LogFactory nullClassLoaderFactory = null;
// --------------------------------------------------------- Static Methods
/**
* Checks whether the supplied Throwable is one that needs to be
* re-thrown and ignores all others.
*
* The following errors are re-thrown:
*
* - ThreadDeath
* - VirtualMachineError
*
*
* @param t the Throwable to check
*/
protected static void handleThrowable(Throwable t) {
if (t instanceof ThreadDeath) {
throw (ThreadDeath) t;
}
if (t instanceof VirtualMachineError) {
throw (VirtualMachineError) t;
}
// All other instances of Throwable will be silently ignored
}
/**
* Opposite to original {@code LogFactory.getFactory}, simply preinstantiated factory is returned.
* No discovery is performed at all.
*
* @throws LogConfigurationException if the implementation class is not
* available or cannot be instantiated.
*/
public static LogFactory getFactory() throws LogConfigurationException {
return m_instance;
}
/**
* 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
* @throws LogConfigurationException if a suitable Log
* instance cannot be returned
*/
public static Log getLog(Class clazz) throws LogConfigurationException {
return getLog(clazz.getName());
}
/**
* 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)
* @throws 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() {
}
// ------------------------------------------------------ Protected Methods
/**
* Safely get access to the classloader for the specified class.
*
* Theoretically, calling getClassLoader can throw a security exception,
* and so should be done under an AccessController in order to provide
* maximum flexibility. However in practice people don't appear to use
* security policies that forbid getClassLoader calls. So for the moment
* all code is written to call this method rather than Class.getClassLoader,
* so that we could put AccessController stuff in this method without any
* disruption later if we need to.
*
* Even when using an AccessController, however, this method can still
* throw SecurityException. Commons-logging basically relies on the
* ability to access classloaders, ie a policy that forbids all
* classloader access will also prevent commons-logging from working:
* currently this method will throw an exception preventing the entire app
* from starting up. Maybe it would be good to detect this situation and
* just disable all commons-logging? Not high priority though - as stated
* above, security policies that prevent classloader access aren't common.
*
* Note that returning an object fetched via an AccessController would
* technically be a security flaw anyway; untrusted code that has access
* to a trusted JCL library could use it to fetch the classloader for
* a class even when forbidden to do so directly.
*
* @since 1.1
*/
protected static ClassLoader getClassLoader(Class clazz) {
return clazz.getClassLoader();
}
/**
* 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.
* @since 1.1
*/
public static String objectId(Object o) {
if (o == null) {
return "null";
} else {
return o.getClass().getName() + "@" + System.identityHashCode(o);
}
}
}