The Tomcat LogFactory.java source code
/*
* 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;
/**
* Modified LogFactory: removed all discovery, hardcode a specific implementation
* If you like a different logging implementation - use either the discovery-based
* commons-logging, or better - another implementation hardcoded to your favourite
* logging impl.
*
* Why ? Each application and deployment can choose a logging implementation -
* that involves configuration, installing the logger jar and optional plugins, etc.
* As part of this process - they can as well install the commons-logging implementation
* that corresponds to their logger of choice. This completely avoids any discovery
* problem, while still allowing the user to switch.
*
* Note that this implementation is not just a wrapper arround 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 - and provides
* no plugin for other LogFactory implementation - 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:
* <p>Factory for creating {@link Log} instances, with discovery and
* configuration features similar to that employed by standard Java APIs
* such as JAXP.</p>
*
* <p>IMPLEMENTATION NOTE - This implementation is heavily
* based on the SAXParserFactory and DocumentBuilderFactory implementations
* (corresponding to the JAXP pluggability APIs) found in Apache Xerces.</p>
*
*
* @author Craig R. McClanahan
* @author Costin Manolache
* @author Richard A. Sitze
* @version $Revision: 467222 $ $Date: 2006-10-24 05:17:11 +0200 (mar., 24 oct. 2006) $
*/
public /* abstract */ class LogFactory {
// ----------------------------------------------------- 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 <code>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";
/**
* <p>Setting this system property value allows the Hashtable used to store
* classloaders to be substituted by an alternative implementation.
* </p>
* <p>
* <strong>Note: LogFactory will print:
* <code> * [ERROR] LogFactory: Load of custom hashtable failed</em>
* </code>
* to system error and then continue using a standard Hashtable.
* </p>
* <p>
* <strong>Usage: Set this property when Java is invoked
* and <code>LogFactory will attempt to load a new instance
* of the given implementation class.
* For example, running the following ant scriplet:
* <code> * <java classname="${test.runner}" fork="yes" failonerror="${test.failonerror}">
* ...
* <sysproperty
* key="org.apache.commons.logging.LogFactory.HashtableImpl"
* value="org.apache.commons.logging.AltHashtable"/>
* </java>
* </pre>
* will mean that <code>LogFactory will load an instance of
* <code>org.apache.commons.logging.AltHashtable.
* </p>
* <p>
* 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 ;)
* </p>
*/
public static final String HASHTABLE_IMPLEMENTATION_PROPERTY =
"org.apache.commons.logging.LogFactory.HashtableImpl";
private static LogFactory singleton=new LogFactory();
Properties logConfig;
// ----------------------------------------------------------- Constructors
/**
* Protected constructor that is not available for public use.
*/
private LogFactory() {
logConfig=new Properties();
}
// hook for syserr logger - class level
void setLogConfig( Properties p ) {
this.logConfig=p;
}
// --------------------------------------------------------- Public Methods
// only those 2 methods need to change to use a different direct logger.
/**
* <p>Construct (if necessary) and return a Log instance,
* using the factory's current set of configuration attributes.</p>
*
* <p>NOTE - Depending upon the implementation of
* the <code>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.</p>
*
* @param name Logical name of the <code>Log instance to be
* returned (the meaning of this name is only known to the underlying
* logging implementation that is being wrapped)
*
* @exception LogConfigurationException if a suitable <code>Log
* instance cannot be returned
*/
public Log getInstance(String name)
throws LogConfigurationException {
return DirectJDKLog.getInstance(name);
}
/**
* 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() {
DirectJDKLog.release();
}
/**
* Return the configuration attribute with the specified name (if any),
* or <code>null if there is no such attribute.
*
* @param name Name of the attribute to return
*/
public Object getAttribute(String name) {
return logConfig.get(name);
}
/**
* 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 (String[])logConfig.keySet().toArray();
}
/**
* 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) {
logConfig.remove(name);
}
/**
* Set the configuration attribute with the specified name. Calling
* this with a <code>null value is equivalent to calling
* <code>removeAttribute(name).
*
* @param name Name of the attribute to set
* @param value Value of the attribute to set, or <code>null
* to remove any setting for this attribute
*/
public void setAttribute(String name, Object value) {
logConfig.put(name, value);
}
/**
* Convenience method to derive a name from the specified class and
* call <code>getInstance(String) with it.
*
* @param clazz Class for which a suitable Log name will be derived
*
* @exception LogConfigurationException if a suitable <code>Log
* 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 LogFactory
* instance, using the following ordered lookup procedure to determine
* the name of the implementation class to be loaded.</p>
* <ul>
* <li>The org.apache.commons.logging.LogFactory system
* property.</li>
* <li>The JDK 1.3 Service Discovery mechanism
* <li>Use the properties file commons-logging.properties
* file, if found in the class path of this class. The configuration
* file is in standard <code>java.util.Properties 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).
* </ul>
*
* <p>NOTE - If the properties file method of identifying the
* <code>LogFactory implementation class is utilized, all of the
* properties defined in this file will be set as configuration attributes
* on the corresponding <code>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
*
* @exception LogConfigurationException if a suitable <code>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 <code>Log instance to be
* returned (the meaning of this name is only known to the underlying
* logging implementation that is being wrapped)
*
* @exception LogConfigurationException if a suitable <code>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 <code>release() on
* each of them.
*
* @param classLoader ClassLoader for which to release the LogFactory
*/
public static void release(ClassLoader classLoader) {
// nothing - we don't use any class loaders
}
/**
* Release any internal references to previously created {@link LogFactory}
* instances, after calling the instance method <code>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() {
singleton.release();
}
/**
* Returns a string that uniquely identifies the specified object, including
* its class.
* <p>
* 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);
}
}
}
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