Field Detail

• LOGGING_IMPL_LOG4J_LOGGER

  private static final java.lang.String LOGGING_IMPL_LOG4J_LOGGER

  Log4JLogger class name

  See Also:

  Constant Field Values

• LOGGING_IMPL_JDK14_LOGGER

  private static final java.lang.String LOGGING_IMPL_JDK14_LOGGER

  Jdk14Logger class name

  See Also:

  Constant Field Values

• LOGGING_IMPL_LUMBERJACK_LOGGER

  private static final java.lang.String LOGGING_IMPL_LUMBERJACK_LOGGER

  Jdk13LumberjackLogger class name

  See Also:

  Constant Field Values

• LOGGING_IMPL_SIMPLE_LOGGER

  private static final java.lang.String LOGGING_IMPL_SIMPLE_LOGGER

  SimpleLog class name

  See Also:

  Constant Field Values

• PKG_IMPL

  private static final java.lang.String PKG_IMPL

  See Also:

  Constant Field Values

• PKG_LEN

  private static final int PKG_LEN

• LOG_PROPERTY

  public static final java.lang.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 java.lang.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 java.lang.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 java.lang.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 java.lang.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

• classesToDiscover

  private static final java.lang.String[] classesToDiscover

  The names of classes that will be tried (in order) as logging adapters. Each class is expected to implement the Log interface, and to throw NoClassDefFound or ExceptionInInitializerError when loaded if the underlying logging library is not available. Any other error indicates that the underlying logging library is available but broken/unusable for some reason.

• useTCCL

  private boolean useTCCL

  Determines whether logging classes should be loaded using the thread-context classloader, or via the classloader that loaded this LogFactoryImpl class.

• diagnosticPrefix

  private java.lang.String diagnosticPrefix

  The string prefixed to every message output by the logDiagnostic method.

• attributes

  protected java.util.Hashtable attributes

  Configuration attributes.

• instances

  protected java.util.Hashtable instances

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

• logClassName

  private java.lang.String logClassName

  Name of the class implementing the Log interface.

• logConstructor

  protected java.lang.reflect.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 java.lang.Class[] logConstructorSignature

  The signature of the Constructor to be used.

• logMethod

  protected java.lang.reflect.Method logMethod

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

• logMethodSignature

  protected java.lang.Class[] logMethodSignature

  The signature of the setLogFactory method to be used.

• allowFlawedContext

  private boolean allowFlawedContext

  See getBaseClassLoader and initConfiguration.

• allowFlawedDiscovery

  private boolean allowFlawedDiscovery

  See handleFlawedDiscovery and initConfiguration.

• allowFlawedHierarchy

  private boolean allowFlawedHierarchy

  See handleFlawedHierarchy and initConfiguration.

Constructor Detail

• LogFactoryImpl

  public LogFactoryImpl()

  Public no-arguments constructor required by the lookup mechanism.

Method Detail

• getAttribute

  public java.lang.Object getAttribute​(java.lang.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 java.lang.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​(java.lang.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​(java.lang.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​(java.lang.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​(java.lang.String name,
                           java.lang.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 java.lang.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 java.lang.ClassLoader getClassLoader​(java.lang.Class clazz)

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

  Since:

  1.1

• initDiagnostics

  private void initDiagnostics()

  Calculate and cache a string that uniquely identifies this instance, including which classloader the object was loaded from.

  This string will later be prefixed to each "internal logging" message emitted, so that users can clearly see any unexpected behaviour.

  Note that this method does not detect whether internal logging is enabled or not, nor where to output stuff if it is; that is all handled by the parent LogFactory class. This method just computes its own unique prefix for log messages.

• logDiagnostic

  protected void logDiagnostic​(java.lang.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 java.lang.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 java.lang.reflect.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​(java.lang.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

• getContextClassLoaderInternal

  private static java.lang.ClassLoader getContextClassLoaderInternal()
                                                              throws LogConfigurationException

  Calls LogFactory.directGetContextClassLoader under the control of an AccessController class. This means that java code running under a security manager that forbids access to ClassLoaders will still work if this class is given appropriate privileges, even when the caller doesn't have such privileges. Without using an AccessController, the the entire call stack must have the privilege before the call is allowed.

  Returns:

  the context classloader associated with the current thread, or null if security doesn't allow it.

  Throws:

  LogConfigurationException - if there was some weird error while attempting to get the context classloader.

  java.lang.SecurityException - if the current java security policy doesn't allow this class to access the context classloader.

• getSystemProperty

  private static java.lang.String getSystemProperty​(java.lang.String key,
                                                    java.lang.String def)
                                             throws java.lang.SecurityException

  Read the specified system property, using an AccessController so that the property can be read if JCL has been granted the appropriate security rights even if the calling code has not.

  Take care not to expose the value returned by this method to the calling application in any way; otherwise the calling app can use that info to access data that should not be available to it.

  Throws:

  java.lang.SecurityException

• getParentClassLoader

  private java.lang.ClassLoader getParentClassLoader​(java.lang.ClassLoader cl)

  Fetch the parent classloader of a specified classloader.

  If a SecurityException occurs, null is returned.

  Note that this method is non-static merely so logDiagnostic is available.

• isLogLibraryAvailable

  private boolean isLogLibraryAvailable​(java.lang.String name,
                                        java.lang.String classname)

  Utility method to check whether a particular logging library is present and available for use. Note that this does not affect the future behaviour of this class.

• getConfigurationValue

  private java.lang.String getConfigurationValue​(java.lang.String property)

  Attempt to find an attribute (see method setAttribute) or a system property with the provided name and return its value.

  The attributes associated with this object are checked before system properties in case someone has explicitly called setAttribute, or a configuration property has been set in a commons-logging.properties file.

  Returns:

  the value associated with the property, or null.

• getBooleanConfiguration

  private boolean getBooleanConfiguration​(java.lang.String key,
                                          boolean dflt)

  Get the setting for the user-configurable behaviour specified by key. If nothing has explicitly been set, then return dflt.

• initConfiguration

  private void initConfiguration()

  Initialize a number of variables that control the behaviour of this class and that can be tweaked by the user. This is done when the first logger is created, not in the constructor of this class, because we need to give the user a chance to call method setAttribute in order to configure this object.

• discoverLogImplementation

  private Log discoverLogImplementation​(java.lang.String logCategory)
                                 throws LogConfigurationException

  Attempts to create a Log instance for the given category name. Follows the discovery process described in the class javadoc.

  Parameters:

  logCategory - the name of the log category

  Throws:

  LogConfigurationException - if an error in discovery occurs, or if no adapter at all can be instantiated

• informUponSimilarName

  private void informUponSimilarName​(java.lang.StringBuffer messageBuffer,
                                     java.lang.String name,
                                     java.lang.String candidate)

  Appends message if the given name is similar to the candidate.

  Parameters:

  messageBuffer - StringBuffer the message should be appended to, not null

  name - the (trimmed) name to be test against the candidate, not null

  candidate - the candidate name (not null)

• findUserSpecifiedLogClassName

  private java.lang.String findUserSpecifiedLogClassName()

  Checks system properties and the attribute map for a Log implementation specified by the user under the property names LOG_PROPERTY or LOG_PROPERTY_OLD.

  Returns:

  classname specified by the user, or null

• createLogFromClass

  private Log createLogFromClass​(java.lang.String logAdapterClassName,
                                 java.lang.String logCategory,
                                 boolean affectState)
                          throws LogConfigurationException

  Attempts to load the given class, find a suitable constructor, and instantiate an instance of Log.

  Parameters:

  logAdapterClassName - classname of the Log implementation

  logCategory - argument to pass to the Log implementation's constructor

  affectState - true if this object's state should be affected by this method call, false otherwise.

  Returns:

  an instance of the given class, or null if the logging library associated with the specified adapter is not available.

  Throws:

  LogConfigurationException - if there was a serious error with configuration and the handleFlawedDiscovery method decided this problem was fatal.

• getBaseClassLoader

  private java.lang.ClassLoader getBaseClassLoader()
                                            throws LogConfigurationException

  Return the classloader from which we should try to load the logging adapter classes.

  This method usually returns the context classloader. However if it is discovered that the classloader which loaded this class is a child of the context classloader and the allowFlawedContext option has been set then the classloader which loaded this class is returned instead.

  The only time when the classloader which loaded this class is a descendant (rather than the same as or an ancestor of the context classloader) is when an app has created custom classloaders but failed to correctly set the context classloader. This is a bug in the calling application; however we provide the option for JCL to simply generate a warning rather than fail outright.

  Throws:

  LogConfigurationException

• getLowestClassLoader

  private java.lang.ClassLoader getLowestClassLoader​(java.lang.ClassLoader c1,
                                                     java.lang.ClassLoader c2)

  Given two related classloaders, return the one which is a child of the other.

  Parameters:

  c1 - is a classloader (including the null classloader)

  c2 - is a classloader (including the null classloader)

  Returns:

  c1 if it has c2 as an ancestor, c2 if it has c1 as an ancestor, and null if neither is an ancestor of the other.

• handleFlawedDiscovery

  private void handleFlawedDiscovery​(java.lang.String logAdapterClassName,
                                     java.lang.ClassLoader classLoader,
                                     java.lang.Throwable discoveryFlaw)

  Generates an internal diagnostic logging of the discovery failure and then throws a LogConfigurationException that wraps the passed Throwable.

  Parameters:

  logAdapterClassName - is the class name of the Log implementation that could not be instantiated. Cannot be null.

  classLoader - is the classloader that we were trying to load the logAdapterClassName from when the exception occurred.

  discoveryFlaw - is the Throwable created by the classloader

  Throws:

  LogConfigurationException - ALWAYS

• handleFlawedHierarchy

  private void handleFlawedHierarchy​(java.lang.ClassLoader badClassLoader,
                                     java.lang.Class badClass)
                              throws LogConfigurationException

  Report a problem loading the log adapter, then either return (if the situation is considered recoverable) or throw a LogConfigurationException.

  There are two possible reasons why we successfully loaded the specified log adapter class then failed to cast it to a Log object:

  1. the specific class just doesn't implement the Log interface (user screwed up), or
  2. the specified class has bound to a Log class loaded by some other classloader; Log@classloaderX cannot be cast to Log@classloaderY.

  Here we try to figure out which case has occurred so we can give the user some reasonable feedback.

  Parameters:

  badClassLoader - is the classloader we loaded the problem class from, ie it is equivalent to badClass.getClassLoader().

  badClass - is a Class object with the desired name, but which does not implement Log correctly.

  Throws:

  LogConfigurationException - when the situation should not be recovered from.