Package org.apache.commons.logging.impl

Class LogFactoryImpl

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

  • 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.

Version:
$Revision: 399224 $ $Date: 2006-05-03 10:25:54 +0100 (Wed, 03 May 2006) $
Author:
Rod Waldhoff, Craig R. McClanahan, Richard A. Sitze, Brian Stansberry

  • Field Details

    • LOG_PROPERTY

      public static final String LOG_PROPERTY
      The name (org.apache.commons.logging.Log) of the system property identifying our Log implementation class.
      See Also:
      Constant Field Values

    • LOG_PROPERTY_OLD

      protected static final String LOG_PROPERTY_OLD
      The deprecated system property used for backwards compatibility with old versions of JCL.
      See Also:
      Constant Field Values

    • 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.
      See Also:
      Constant Field Values

    • 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.
      See Also:
      Constant Field Values

    • 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.
      See Also:
      Constant Field Values

    • 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.

  • Constructor Details

    • LogFactoryImpl

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

  • Method Details

    • getAttribute

      public Object getAttribute​(String name)
      Return the configuration attribute with the specified name (if any), or null if there is no such attribute.
      Specified by:
      getAttribute in class LogFactory
      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.
      Specified by:
      getAttributeNames in class LogFactory

    • getInstance

      public Log getInstance​(Class clazz) throws LogConfigurationException
      Convenience method to derive a name from the specified class and call getInstance(String) with it.
      Specified by:
      getInstance in class LogFactory
      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) 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.

      Specified by:
      getInstance in class LogFactory
      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 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.
      Specified by:
      release in class LogFactory

    • 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.
      Specified by:
      removeAttribute in class LogFactory
      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.

      Specified by:
      setAttribute in class LogFactory
      Parameters:
      name - Name of the attribute to set
      value - Value of the attribute to set, or null to remove any setting for this attribute

    • getContextClassLoader

      protected static ClassLoader getContextClassLoader() throws LogConfigurationException
      Gets the context classloader. This method is a workaround for a java 1.2 compiler bug.
      Throws:
      LogConfigurationException
      Since:
      1.1

    • isDiagnosticsEnabled

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

    • 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

    • 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

    • 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() throws LogConfigurationException
      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

    • 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?

    • newInstance

      protected Log newInstance​(String name) throws LogConfigurationException
      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