Class LogFactory
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 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.
- Author:
- Craig R. McClanahan, Costin Manolache, Richard A. Sitze
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Method Summary
Modifier and TypeMethodDescriptionstatic LogFactoryConstruct (if necessary) and return aLogFactoryinstance, using the following ordered lookup procedure to determine the name of the implementation class to be loaded.getInstance(Class<?> clazz) Convenience method to derive a name from the specified class and callgetInstance(String)with it.getInstance(String name) Construct (if necessary) and return aLoginstance, using the factory's current set of configuration attributes.static LogConvenience method to return a named logger, without the application having to care about factories.static LogConvenience method to return a named logger, without the application having to care about factories.static voidrelease(ClassLoader classLoader) Release any internal references to previously createdLogFactoryinstances that have been associated with the specified class loader (if any), after calling the instance methodrelease()on each of them.
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Method Details
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getInstance
Construct (if necessary) and return a
Loginstance, using the factory's current set of configuration attributes.NOTE - Depending upon the implementation of the
LogFactoryyou are using, theLoginstance 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.- Parameters:
name- Logical name of theLoginstance to be returned (the meaning of this name is only known to the underlying logging implementation that is being wrapped)- Returns:
- A log instance with the requested name
- Throws:
LogConfigurationException- if a suitableLoginstance cannot be returned
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getInstance
Convenience method to derive a name from the specified class and callgetInstance(String)with it.- Parameters:
clazz- Class for which a suitable Log name will be derived- Returns:
- A log instance with a name of clazz.getName()
- Throws:
LogConfigurationException- if a suitableLoginstance cannot be returned
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getFactory
Construct (if necessary) and return a
LogFactoryinstance, using the following ordered lookup procedure to determine the name of the implementation class to be loaded.- The
org.apache.commons.logging.LogFactorysystem property. - The JDK 1.3 Service Discovery mechanism
- Use the properties file
commons-logging.propertiesfile, if found in the class path of this class. The configuration file is in standardjava.util.Propertiesformat 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
LogFactoryimplementation class is utilized, all of the properties defined in this file will be set as configuration attributes on the correspondingLogFactoryinstance.- Returns:
- The singleton LogFactory instance
- Throws:
LogConfigurationException- if the implementation class is not available or cannot be instantiated.
- The
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getLog
Convenience method to return a named logger, without the application having to care about factories.- Parameters:
clazz- Class from which a log name will be derived- Returns:
- A log instance with a name of clazz.getName()
- Throws:
LogConfigurationException- if a suitableLoginstance cannot be returned
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getLog
Convenience method to return a named logger, without the application having to care about factories.- Parameters:
name- Logical name of theLoginstance to be returned (the meaning of this name is only known to the underlying logging implementation that is being wrapped)- Returns:
- A log instance with the requested name
- Throws:
LogConfigurationException- if a suitableLoginstance cannot be returned
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release
Release any internal references to previously createdLogFactoryinstances that have been associated with the specified class loader (if any), after calling the instance methodrelease()on each of them.- Parameters:
classLoader- ClassLoader for which to release the LogFactory
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