org.apache.commons.logging
Class LogFactory

java.lang.Object
  org.apache.commons.logging.LogFactory

Direct Known Subclasses:

SLF4JLogFactory

public abstract class LogFactory
extends Object

Factory for creating Log instances, which always delegates to an instance of SLF4JLogFactory.

Author:

Craig R. McClanahan, Costin Manolache, Richard A. Sitze, Ceki Gülcü

Field Summary

static String	FACTORY_DEFAULT The fully qualified class name of the fallback LogFactory implementation class to use, if no other can be found.
static String	FACTORY_PROPERTIES The name of the properties file to search for.
static String	FACTORY_PROPERTY The name of the property used to identify the LogFactory implementation class name.

Constructor Summary

protected

LogFactory() Protected constructor that is not available for public use.

Method Summary

abstract Object	getAttribute(String name) Return the configuration attribute with the specified name (if any), or null if there is no such attribute.
abstract String[]	getAttributeNames() Return an array containing the names of all currently defined configuration attributes.
static LogFactory	getFactory() 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.
abstract Log	getInstance(Class clazz) Convenience method to derive a name from the specified class and call getInstance(String) with it.
abstract Log	getInstance(String name) Construct (if necessary) and return a Log instance, using the factory's current set of configuration attributes.
static Log	getLog(Class clazz) Convenience method to return a named logger, without the application having to care about factories.
static Log	getLog(String name) Convenience method to return a named logger, without the application having to care about factories.
abstract void	release() Release any internal references to previously created Loginstances returned by this factory.
static void	release(ClassLoader classLoader) Release any internal references to previously created LogFactory instances that have been associated with the specified class loader (if any), after calling the instance method release() on each of them.
static void	releaseAll() Release any internal references to previously created LogFactory instances, after calling the instance method release() on each of them.
abstract void	removeAttribute(String name) Remove any configuration attribute associated with the specified name.
abstract void	setAttribute(String name, Object value) Set the configuration attribute with the specified name.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FACTORY_PROPERTY

public static final String FACTORY_PROPERTY

The name of the property used to identify the LogFactory implementation class name.

This property is not used but preserved here for compatibility.

See Also:

Constant Field Values

FACTORY_DEFAULT

public static final String FACTORY_DEFAULT

The fully qualified class name of the fallback LogFactory implementation class to use, if no other can be found.

This property is not used but preserved here for compatibility.

See Also:

Constant Field Values

FACTORY_PROPERTIES

public static final String FACTORY_PROPERTIES

The name of the properties file to search for.

This property is not used but preserved here for compatibility.

See Also:

Constant Field Values

Constructor Detail

LogFactory

protected LogFactory()

Protected constructor that is not available for public use.

Method Detail

getAttribute

public abstract Object getAttribute(String name)

Return the configuration attribute with the specified name (if any), or null if there is no such attribute.

Parameters:

name - Name of the attribute to return

getAttributeNames

public abstract String[] getAttributeNames()

Return an array containing the names of all currently defined configuration attributes. If there are no such attributes, a zero length array is returned.

getInstance

public abstract Log getInstance(Class clazz)
                         throws LogConfigurationException

Convenience method to derive a name from the specified class and call getInstance(String) with it.

Parameters:

clazz - Class for which a suitable Log name will be derived

Throws:

LogConfigurationException - if a suitable Log instance cannot be returned

getInstance

public abstract Log getInstance(String name)
                         throws LogConfigurationException

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.

Parameters:

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

release

public abstract void release()

Release any internal references to previously created Loginstances 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.

removeAttribute

public abstract void removeAttribute(String name)

Remove any configuration attribute associated with the specified name. If there is no such attribute, no action is taken.

Parameters:

name - Name of the attribute to remove

setAttribute

public abstract void setAttribute(String name,
                                  Object value)

Set the configuration attribute with the specified name. Calling this with a null value is equivalent to calling removeAttribute(name).

Parameters:

name - Name of the attribute to set

value - Value of the attribute to set, or null to remove any setting for this attribute

getFactory

public static LogFactory getFactory()
                             throws LogConfigurationException

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.SLF4FLogFactory).

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.

Throws:

LogConfigurationException - if the implementation class is not available or cannot be instantiated.

getLog

public static Log getLog(Class clazz)
                  throws LogConfigurationException

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

Throws:

LogConfigurationException - if a suitable Log instance cannot be returned

getLog

public static Log getLog(String name)
                  throws LogConfigurationException

Convenience method to return a named logger, without the application having to care about factories.

Parameters:

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

release

public static void release(ClassLoader classLoader)

Release any internal references to previously created LogFactory instances that have been associated with the specified class loader (if any), after calling the instance method release() on each of them.

Parameters:

classLoader - ClassLoader for which to release the LogFactory

releaseAll

public static void releaseAll()

Release any internal references to previously created 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.