org.apache.commons.logging.impl

Class LogFactoryImpl

public class LogFactoryImpl extends LogFactory

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

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.

Field Summary
static StringALLOW_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.
static StringALLOW_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.
static StringALLOW_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.
protected Hashtableattributes
Configuration attributes.
protected Hashtableinstances
The Log instances that have already been created, keyed by logger name.
protected ConstructorlogConstructor
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 MethodlogMethod
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.
static StringLOG_PROPERTY
The name (org.apache.commons.logging.Log) of the system property identifying our Log implementation class.
protected static StringLOG_PROPERTY_OLD
The deprecated system property used for backwards compatibility with old versions of JCL.
Constructor Summary
LogFactoryImpl()
Public no-arguments constructor required by the lookup mechanism.
Method Summary
ObjectgetAttribute(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.
protected static ClassLoadergetClassLoader(Class clazz)
Workaround for bug in Java1.2; in theory this method is not needed.
protected static ClassLoadergetContextClassLoader()
Gets the context classloader.
LoggetInstance(Class clazz)
Convenience method to derive a name from the specified class and call getInstance(String) with it.
LoggetInstance(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.

protected StringgetLogClassName()
Return the fully qualified Java classname of the Log implementation we will be using.
protected ConstructorgetLogConstructor()

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.

protected static booleanisDiagnosticsEnabled()
Workaround for bug in Java1.2; in theory this method is not needed.
protected booleanisJdk13LumberjackAvailable()
Is JDK 1.3 with Lumberjack logging available?
protected booleanisJdk14Available()

Return true if JDK 1.4 or later logging is available.

protected booleanisLog4JAvailable()
Is a Log4J implementation available?
protected voidlogDiagnostic(String msg)
Output a diagnostic message to a user-specified destination (if the user has enabled diagnostic logging).
protected LognewInstance(String name)
Create and return a new Log instance for the specified name.
voidrelease()
Release any internal references to previously created Log instances returned by this factory.
voidremoveAttribute(String name)
Remove any configuration attribute associated with the specified name.
voidsetAttribute(String name, Object value)
Set the configuration attribute with the specified name.

Field Detail

ALLOW_FLAWED_CONTEXT_PROPERTY

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.

ALLOW_FLAWED_DISCOVERY_PROPERTY

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.

ALLOW_FLAWED_HIERARCHY_PROPERTY

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.

attributes

protected Hashtable attributes
Configuration attributes.

instances

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

logConstructor

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.

logConstructorSignature

protected Class[] logConstructorSignature
The signature of the Constructor to be used.

logMethod

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

logMethodSignature

protected Class[] logMethodSignature
The signature of the setLogFactory method to be used.

LOG_PROPERTY

public static final String LOG_PROPERTY
The name (org.apache.commons.logging.Log) of the system property identifying our Log implementation class.

LOG_PROPERTY_OLD

protected static final String LOG_PROPERTY_OLD
The deprecated system property used for backwards compatibility with old versions of JCL.

Constructor Detail

LogFactoryImpl

public LogFactoryImpl()
Public no-arguments constructor required by the lookup mechanism.

Method Detail

getAttribute

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

getAttributeNames

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.

getClassLoader

protected static ClassLoader getClassLoader(Class clazz)
Workaround for bug in Java1.2; in theory this method is not needed. See LogFactory.getClassLoader.

Since: 1.1

getContextClassLoader

protected static ClassLoader getContextClassLoader()
Gets the context classloader. This method is a workaround for a java 1.2 compiler bug.

Since: 1.1

getInstance

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

getInstance

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

getLogClassName

protected String getLogClassName()

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.

getLogConstructor

protected Constructor getLogConstructor()

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

isDiagnosticsEnabled

protected static boolean isDiagnosticsEnabled()
Workaround for bug in Java1.2; in theory this method is not needed. See LogFactory.isDiagnosticsEnabled.

isJdk13LumberjackAvailable

protected boolean isJdk13LumberjackAvailable()

Deprecated: Never invoked by this class; subclasses should not assume it will be.

Is JDK 1.3 with Lumberjack logging available?

isJdk14Available

protected boolean isJdk14Available()

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.

isLog4JAvailable

protected boolean isLog4JAvailable()

Deprecated: Never invoked by this class; subclasses should not assume it will be.

Is a Log4J implementation available?

logDiagnostic

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

Since: 1.1

newInstance

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

release

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.

removeAttribute

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

setAttribute

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