org.apache.commons.logging
Class LogFactory

java.lang.Object
  extended by 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 DIAGNOSTICS_DEST_PROPERTY
          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.
protected static Hashtable factories
          The previously constructed LogFactory instances, keyed by the ClassLoader with which it was created.
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.
static String HASHTABLE_IMPLEMENTATION_PROPERTY
           Setting this system property value allows the Hashtable used to store classloaders to be substituted by an alternative implementation.
protected static LogFactory nullClassLoaderFactory
           This property is not used but preserved here for compatibility.
static String PRIORITY_KEY
          The name (priority) of the key in the config file used to specify the priority of that particular config file.
protected static String SERVICE_ID
          JDK1.3+ 'Service Provider' specification.
static String TCCL_KEY
          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.
 
Constructor Summary
protected LogFactory()
          Protected constructor that is not available for public use.
 
Method Summary
protected static Object createFactory(String factoryClass, ClassLoader classLoader)
          This method exists to ensure signature compatibility.
protected static ClassLoader directGetContextClassLoader()
          This method exists to ensure signature compatibility.
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.
protected static ClassLoader getClassLoader(Class clazz)
          This method exists to ensure signature compatibility.
protected static ClassLoader getContextClassLoader()
          This method exists to ensure signature compatibility.
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.
protected static boolean isDiagnosticsEnabled()
          This method exists to ensure signature compatibility.
protected static void logRawDiagnostic(String msg)
          This method exists to ensure signature compatibility.
protected static LogFactory newFactory(String factoryClass, ClassLoader classLoader)
          This method exists to ensure signature compatibility.
protected static LogFactory newFactory(String factoryClass, ClassLoader classLoader, ClassLoader contextClassLoader)
          This method exists to ensure signature compatibility.
static String objectId(Object o)
          Returns a string that uniquely identifies the specified object, including its class.
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

PRIORITY_KEY

public static final String PRIORITY_KEY
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.

This property is not used but preserved here for compatibility.

See Also:
Constant Field Values

TCCL_KEY

public static final String TCCL_KEY
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.

This property is not used but preserved here for compatibility.

See Also:
Constant Field Values

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

SERVICE_ID

protected static final String SERVICE_ID
JDK1.3+ 'Service Provider' specification.

This property is not used but preserved here for compatibility.

See Also:
Constant Field Values

DIAGNOSTICS_DEST_PROPERTY

public static final String DIAGNOSTICS_DEST_PROPERTY
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.

This property is not used but preserved here for compatibility.

See Also:
Constant Field Values

HASHTABLE_IMPLEMENTATION_PROPERTY

public static final String HASHTABLE_IMPLEMENTATION_PROPERTY

Setting this system property value allows the Hashtable used to store classloaders to be substituted by an alternative implementation.

This property is not used but preserved here for compatibility.

See Also:
Constant Field Values

factories

protected static Hashtable factories
The previously constructed LogFactory instances, keyed by the ClassLoader with which it was created.

This property is not used but preserved here for compatibility.


nullClassLoaderFactory

protected static LogFactory nullClassLoaderFactory

This property is not used but preserved here for compatibility.

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
Returns:
configuration attribute

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.

Returns:
names of all currently defined configuration attributes

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.

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.


objectId

public static String objectId(Object o)
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.

Parameters:
o - may be null.
Returns:
a string of form classname@hashcode, or "null" if param o is null.
Since:
1.1

createFactory

protected static Object createFactory(String factoryClass,
                                      ClassLoader classLoader)
This method exists to ensure signature compatibility.


directGetContextClassLoader

protected static ClassLoader directGetContextClassLoader()
This method exists to ensure signature compatibility.


getContextClassLoader

protected static ClassLoader getContextClassLoader()
                                            throws LogConfigurationException
This method exists to ensure signature compatibility.

Throws:
LogConfigurationException

getClassLoader

protected static ClassLoader getClassLoader(Class clazz)
This method exists to ensure signature compatibility.


isDiagnosticsEnabled

protected static boolean isDiagnosticsEnabled()
This method exists to ensure signature compatibility.


logRawDiagnostic

protected static void logRawDiagnostic(String msg)
This method exists to ensure signature compatibility.


newFactory

protected static LogFactory newFactory(String factoryClass,
                                       ClassLoader classLoader,
                                       ClassLoader contextClassLoader)
This method exists to ensure signature compatibility.


newFactory

protected static LogFactory newFactory(String factoryClass,
                                       ClassLoader classLoader)
This method exists to ensure signature compatibility.



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