Class LogFactory

  • Direct Known Subclasses:
    SLF4JLogFactory

    public abstract class LogFactory
    extends Object

    Factory for creating Log instances, which always delegates to an instance of SLF4JLogFactory.

    Author:
    Craig R. McClanahan, Costin Manolache, Richard A. Sitze, Ceki Gülcü
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static String DIAGNOSTICS_DEST_PROPERTY
      The name (org.apache.commons.logging.diagnostics.dest) of the property used to enable internal commons-logging diagnostic output, in order to get information on what logging implementations are being discovered, what classloaders they are loaded through, etc.
      protected static Hashtable factories
      The previously constructed LogFactory instances, keyed by the ClassLoader with which it was created.
      static String FACTORY_DEFAULT
      The fully qualified class name of the fallback LogFactory implementation class to use, if no other can be found.
      static String FACTORY_PROPERTIES
      The name of the properties file to search for.
      static String FACTORY_PROPERTY
      The name of the property used to identify the LogFactory implementation class name.
      static String HASHTABLE_IMPLEMENTATION_PROPERTY
      Setting this system property value allows the Hashtable used to store classloaders to be substituted by an alternative implementation.
      protected static LogFactory nullClassLoaderFactory
      This property is not used but preserved here for compatibility.
      static String PRIORITY_KEY
      The name (priority) of the key in the config file used to specify the priority of that particular config file.
      protected static String SERVICE_ID
      static String TCCL_KEY
      The name (use_tccl) of the key in the config file used to specify whether logging classes should be loaded via the thread context class loader (TCCL), or not.
    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected LogFactory()
      Protected constructor that is not available for public use.
    • Field Detail

      • PRIORITY_KEY

        public static final String PRIORITY_KEY
        The name (priority) of the key in the config file used to specify the priority of that particular config file. The associated value is a floating-point number; higher values take priority over lower values.

        This property is not used but preserved here for compatibility.

        See Also:
        Constant Field Values
      • TCCL_KEY

        public static final String TCCL_KEY
        The name (use_tccl) of the key in the config file used to specify whether logging classes should be loaded via the thread context class loader (TCCL), or not. By default, the TCCL is used.

        This property is not used but preserved here for compatibility.

        See Also:
        Constant Field Values
      • FACTORY_PROPERTY

        public static final String FACTORY_PROPERTY
        The name of the property used to identify the LogFactory implementation class name.

        This property is not used but preserved here for compatibility.

        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.

        This property is not used but preserved here for compatibility.

        See Also:
        Constant Field Values
      • DIAGNOSTICS_DEST_PROPERTY

        public static final String DIAGNOSTICS_DEST_PROPERTY
        The name (org.apache.commons.logging.diagnostics.dest) of the property used to enable internal commons-logging diagnostic output, in order to get information on what logging implementations are being discovered, what classloaders they are loaded through, etc.

        This property is not used but preserved here for compatibility.

        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.

        This property is not used but preserved here for compatibility.

        See Also:
        Constant Field Values
      • factories

        protected static Hashtable factories
        The previously constructed LogFactory instances, keyed by the ClassLoader with which it was created.

        This property is not used but preserved here for compatibility.

    • Constructor Detail

      • LogFactory

        protected LogFactory()
        Protected constructor that is not available for public use.
    • Method Detail

      • getAttribute

        public abstract 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
        Returns:
        configuration attribute
      • getAttributeNames

        public abstract 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.
        Returns:
        names of all currently defined configuration attributes
      • getInstance

        public abstract 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
        Throws:
        LogConfigurationException - if a suitable Log instance cannot be returned
      • getInstance

        public abstract 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)
        Throws:
        LogConfigurationException - if a suitable Log instance cannot be returned
      • release

        public abstract void release()
        Release any internal references to previously created Loginstances 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 abstract 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 abstract 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
      • 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.SLF4FLogFactory).

        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.

        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
        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)
        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", i.e. 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.
        Since:
        1.1
      • isDiagnosticsEnabled

        protected static boolean isDiagnosticsEnabled()
        This method exists to ensure signature compatibility.
      • logRawDiagnostic

        protected static void logRawDiagnostic​(String msg)
        This method exists to ensure signature compatibility.