public class

LogFactoryImpl

extends LogFactory
java.lang.Object
   ↳ org.apache.commons.logging.LogFactory
     ↳ org.apache.commons.logging.impl.LogFactoryImpl

Class Overview

Concrete subclass of LogFactory that implements the following algorithm to dynamically select a logging implementation class to instantiate a wrapper for.

  • Use a factory configuration attribute named org.apache.commons.logging.Log to identify the requested implementation class.
  • Use the org.apache.commons.logging.Log system property to identify the requested implementation class.
  • If Log4J is available, return an instance of org.apache.commons.logging.impl.Log4JLogger.
  • If JDK 1.4 or later is available, return an instance of org.apache.commons.logging.impl.Jdk14Logger.
  • Otherwise, return an instance of org.apache.commons.logging.impl.SimpleLog.

If the selected Log implementation class has a setLogFactory() method that accepts a LogFactory parameter, this method will be called on each newly created instance to identify the associated factory. This makes factory configuration attributes available to the Log instance, if it so desires.

This factory will remember previously created Log instances for the same name, and will return them on repeated requests to the getInstance() method.

Summary

Constants
String ALLOW_FLAWED_CONTEXT_PROPERTY The name (org.apache.commons.logging.Log.allowFlawedContext) of the system property which can be set true/false to determine system behaviour when a bad context-classloader is encountered.
String ALLOW_FLAWED_DISCOVERY_PROPERTY The name (org.apache.commons.logging.Log.allowFlawedDiscovery) of the system property which can be set true/false to determine system behaviour when a bad logging adapter class is encountered during logging discovery.
String ALLOW_FLAWED_HIERARCHY_PROPERTY The name (org.apache.commons.logging.Log.allowFlawedHierarchy) of the system property which can be set true/false to determine system behaviour when a logging adapter class is encountered which has bound to the wrong Log class implementation.
String LOG_PROPERTY The name (org.apache.commons.logging.Log) of the system property identifying our Log implementation class.
String LOG_PROPERTY_OLD The deprecated system property used for backwards compatibility with old versions of JCL.
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Inherited Constants
From class org.apache.commons.logging.LogFactory
Fields
protected Hashtable attributes Configuration attributes.
protected Hashtable instances The Log instances that have already been created, keyed by logger name.
protected Constructor logConstructor The one-argument constructor of the Log implementation class that will be used to create new instances.
protected Class[] logConstructorSignature The signature of the Constructor to be used.
protected Method logMethod The one-argument setLogFactory method of the selected Log method, if it exists.
protected Class[] logMethodSignature The signature of the setLogFactory method to be used.
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Inherited Fields
From class org.apache.commons.logging.LogFactory
Public Constructors
LogFactoryImpl()
Public no-arguments constructor required by the lookup mechanism.
Public Methods
Object getAttribute(String name)
Return the configuration attribute with the specified name (if any), or null if there is no such attribute.
String[] getAttributeNames()
Return an array containing the names of all currently defined configuration attributes.
Log getInstance(String name)

Construct (if necessary) and return a Log instance, using the factory's current set of configuration attributes.

Log getInstance(Class clazz)
Convenience method to derive a name from the specified class and call getInstance(String) with it.
void release()
Release any internal references to previously created Log instances returned by this factory.
void removeAttribute(String name)
Remove any configuration attribute associated with the specified name.
void setAttribute(String name, Object value)
Set the configuration attribute with the specified name.
Protected Methods
static ClassLoader getClassLoader(Class clazz)
Workaround for bug in Java1.2; in theory this method is not needed.
static ClassLoader getContextClassLoader()
Gets the context classloader.
String getLogClassName()
This method is deprecated. Never invoked by this class; subclasses should not assume it will be.
Constructor getLogConstructor()
This method is deprecated. Never invoked by this class; subclasses should not assume it will be.
static boolean isDiagnosticsEnabled()
Workaround for bug in Java1.2; in theory this method is not needed.
boolean isJdk13LumberjackAvailable()
This method is deprecated. Never invoked by this class; subclasses should not assume it will be.
boolean isJdk14Available()
This method is deprecated. Never invoked by this class; subclasses should not assume it will be.
boolean isLog4JAvailable()
This method is deprecated. Never invoked by this class; subclasses should not assume it will be.
void logDiagnostic(String msg)
Output a diagnostic message to a user-specified destination (if the user has enabled diagnostic logging).
Log newInstance(String name)
Create and return a new Log instance for the specified name.
[Expand]
Inherited Methods
From class org.apache.commons.logging.LogFactory
From class java.lang.Object

Constants

public static final String ALLOW_FLAWED_CONTEXT_PROPERTY

The name (org.apache.commons.logging.Log.allowFlawedContext) of the system property which can be set true/false to determine system behaviour when a bad context-classloader is encountered. When set to false, a LogConfigurationException is thrown if LogFactoryImpl is loaded via a child classloader of the TCCL (this should never happen in sane systems). Default behaviour: true (tolerates bad context classloaders) See also method setAttribute.

Constant Value: "org.apache.commons.logging.Log.allowFlawedContext"

public static final String ALLOW_FLAWED_DISCOVERY_PROPERTY

The name (org.apache.commons.logging.Log.allowFlawedDiscovery) of the system property which can be set true/false to determine system behaviour when a bad logging adapter class is encountered during logging discovery. When set to false, an exception will be thrown and the app will fail to start. When set to true, discovery will continue (though the user might end up with a different logging implementation than they expected). Default behaviour: true (tolerates bad logging adapters) See also method setAttribute.

Constant Value: "org.apache.commons.logging.Log.allowFlawedDiscovery"

public static final String ALLOW_FLAWED_HIERARCHY_PROPERTY

The name (org.apache.commons.logging.Log.allowFlawedHierarchy) of the system property which can be set true/false to determine system behaviour when a logging adapter class is encountered which has bound to the wrong Log class implementation. When set to false, an exception will be thrown and the app will fail to start. When set to true, discovery will continue (though the user might end up with a different logging implementation than they expected). Default behaviour: true (tolerates bad Log class hierarchy) See also method setAttribute.

Constant Value: "org.apache.commons.logging.Log.allowFlawedHierarchy"

public static final String LOG_PROPERTY

The name (org.apache.commons.logging.Log) of the system property identifying our Log implementation class.

Constant Value: "org.apache.commons.logging.Log"

protected static final String LOG_PROPERTY_OLD

The deprecated system property used for backwards compatibility with old versions of JCL.

Constant Value: "org.apache.commons.logging.log"

Fields

protected Hashtable attributes

Configuration attributes.

protected Hashtable instances

The Log instances that have already been created, keyed by logger name.

protected Constructor logConstructor

The one-argument constructor of the Log implementation class that will be used to create new instances. This value is initialized by getLogConstructor(), and then returned repeatedly.

protected Class[] logConstructorSignature

The signature of the Constructor to be used.

protected Method logMethod

The one-argument setLogFactory method of the selected Log method, if it exists.

protected Class[] logMethodSignature

The signature of the setLogFactory method to be used.

Public Constructors

public LogFactoryImpl ()

Public no-arguments constructor required by the lookup mechanism.

Public Methods

public 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

public 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.

public Log getInstance (String name)

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

public Log getInstance (Class clazz)

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

public void release ()

Release any internal references to previously created 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 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

public 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).

This method can be used to set logging configuration programmatically rather than via system properties. It can also be used in code running within a container (such as a webapp) to configure behaviour on a per-component level instead of globally as system properties would do. To use this method instead of a system property, call 

 LogFactory.getFactory().setAttribute(...)
This must be done before the first Log object is created; configuration changes after that point will be ignored.

This method is also called automatically if LogFactory detects a commons-logging.properties file; every entry in that file is set automatically as an attribute here.

Parameters
name Name of the attribute to set
value Value of the attribute to set, or null to remove any setting for this attribute

Protected Methods

protected static ClassLoader getClassLoader (Class clazz)

Workaround for bug in Java1.2; in theory this method is not needed. See LogFactory.getClassLoader.

protected static ClassLoader getContextClassLoader ()

Gets the context classloader. This method is a workaround for a java 1.2 compiler bug.

Throws
LogConfigurationException

protected String getLogClassName ()

This method is deprecated.
Never invoked by this class; subclasses should not assume it will be.

Return the fully qualified Java classname of the Log implementation we will be using.

protected Constructor getLogConstructor ()

This method is deprecated.
Never invoked by this class; subclasses should not assume it will be.

Return the Constructor that can be called to instantiate new Log instances.

IMPLEMENTATION NOTE - Race conditions caused by calling this method from more than one thread are ignored, because the same Constructor instance will ultimately be derived in all circumstances.

Throws
LogConfigurationException if a suitable constructor cannot be returned

protected static boolean isDiagnosticsEnabled ()

Workaround for bug in Java1.2; in theory this method is not needed. See LogFactory.isDiagnosticsEnabled.

protected boolean isJdk13LumberjackAvailable ()

This method is deprecated.
Never invoked by this class; subclasses should not assume it will be.

Is JDK 1.3 with Lumberjack logging available?

protected boolean isJdk14Available ()

This method is deprecated.
Never invoked by this class; subclasses should not assume it will be.

Return true if JDK 1.4 or later logging is available. Also checks that the Throwable class supports getStackTrace(), which is required by Jdk14Logger.

protected boolean isLog4JAvailable ()

This method is deprecated.
Never invoked by this class; subclasses should not assume it will be.

Is a Log4J implementation available?

protected void logDiagnostic (String msg)

Output a diagnostic message to a user-specified destination (if the user has enabled diagnostic logging).

Parameters
msg diagnostic message

protected Log newInstance (String name)

Create and return a new Log instance for the specified name.

Parameters
name Name of the new logger
Throws
LogConfigurationException if a new instance cannot be created