Field Detail

• FACTORY_PROPERTY

  public static final String FACTORY_PROPERTY

  The name of the property used to identify the LogFactory implementation class name.

  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.

  See Also:

  Constant Field Values

• FACTORY_PROPERTIES

  public static final String FACTORY_PROPERTIES

  The name of the properties file to search for.

  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.

  Note: LogFactory will print:

   [ERROR] LogFactory: Load of custom hashtable failed
   

  to system error and then continue using a standard Hashtable.

  Usage: Set this property when Java is invoked and LogFactory will attempt to load a new instance of the given implementation class. For example, running the following ant scriptlet:

    <java classname="${test.runner}" fork="yes" failonerror="${test.failonerror}">
       ...
       <sysproperty
          key="org.apache.commons.logging.LogFactory.HashtableImpl"
          value="org.apache.commons.logging.AltHashtable"/>
    </java>
   

  will mean that LogFactory will load an instance of org.apache.commons.logging.AltHashtable.

  A typical use case is to allow a custom Hashtable implementation using weak references to be substituted. This will allow classloaders to be garbage collected without the need to release them (on 1.3+ JVMs only, of course ;)

  See Also:

  Constant Field Values

Method Detail

• 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.

  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)

  Returns:

  A log instance with the requested name

  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.

• 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.

• 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).

  Parameters:

  name - Name of the attribute to set

  value - Value of the attribute to set, or null to remove any setting for this attribute

• getInstance

  public 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

  Returns:

  A log instance with a name of clazz.getName()

  Throws:

  LogConfigurationException - if a suitable Log instance cannot be returned

• 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.

  • The org.apache.commons.logging.LogFactory system property.
  • The JDK 1.3 Service Discovery mechanism
  • Use the properties file commons-logging.properties file, if found in the class path of this class. The configuration file is in standard java.util.Properties format and contains the fully qualified name of the implementation class with the key being the system property defined above.
  • Fall back to a default implementation class (org.apache.commons.logging.impl.LogFactoryImpl).

  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.

  Returns:

  The singleton 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

  Returns:

  A log instance with a name of clazz.getName()

  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)

  Returns:

  A log instance with the requested name

  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 overridden the toString method.

  Parameters:

  o - may be null.

  Returns:

  a string of form classname@hashcode, or "null" if param o is null.