Documentation of 'org.clapper.util.logging.Logger' Java class
Logger
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org.clapper.util.logging

Class Logger


  • public class Logger
extends java.lang.Object

    Logger wraps the Jakarta Commons Logging API and provides a slightly simpler, but similar, interface. This class supports most of the logging methods, but it doesn't actually instantiate an underlying java.util.logging.Logger object until (or unless) a thread explicitly calls the enableLogging() method. The first call to enableLogging() traverses the list of instantiated org.clapper.util.Logger objects and creates underlying java.util.logging.Logger objects for each one. Any Logger objects created after enableLogging() is called are automatically enabled.

    This approach prevents any interaction with the real logging layer, unless logging is explicitly enabled (e.g., because a command-line option has been specified). This approach was originally taken to avoid annoying startup messages from the Log4J logging implementation, which insists on writing warning messages to the console when it can't find a configuration file.

    However, this class can be reimplemented in terms of other logging layers (and, in fact, has been implemented solely in terms of the JDK 1.4 native logging library in the past).

    This object's main purpose now is to insulate applications from the underlying logging technology, so that technology can be changed, if necessary, without having an impact on applications that use this class.

    The level mappings used by this class are identical to those used by Commons Logging. (e.g.,, a "debug" message uses the same level as a Commons Logging "debug" message.) Those mappings are:

    org.clapper.util.logging.Logger method Corresponding java.util.logging.Level value
    debug() FINE
    error() SEVERE
    fatal() SEVERE
    info() INFO
    trace() FINEST
    warn() WARNING

    If you prefer to use Commons Logging directly, then, by all means, use it for your applications.

    WARNING: If your application installs its own class loader (e.g., as the thread context class loader), you may have problems with both Jakarta Commons Logging and java.util.logging (which Jakarta Commons Logging uses as its default logging implementation).

    • The java.util.logging layer explicitly bootstraps itself using the system class loader (i.e., the class loader that examines the CLASSPATH setting). In some cases, this can cause problems. For instance, an application that installs its own class loader and expects to use that class loader to find a custom-built java.util.logging formatter will not end up using its own formatter, because the formatter class is not available in the CLASSPATH, and that's where java.util.logging expects to find it. In situations like that, the best bet is to substitute a better-behaved underlying logging layer such as Log4J.
    • Jakarta Commons Logging uses a "discovery" process that plays class loader games. You can solve the problem with Commons Logging by explicitly specifying the underlying logging API to use. For example: 
       java -Dorg.apache.commons.logging.Log=org.apache.commons.logging.impl.Log4JLogger -Dlog4j.configuration=file:/path/to/log4j-debug.properties
    See Also:
    enableLogging(), Jakarta Commons Logging API

    • Constructor Summary

      Constructors 
      Constructor and Description
      Logger(java.lang.Class cls)
      Construct a new Logger object
      Logger(java.lang.String className)
      Construct a new Logger object

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method and Description
      void debug(java.lang.Object message)
      Log a message with debug log level.
      void debug(java.lang.Object message, java.lang.Throwable ex)
      Log an error with debug log level.
      static void enableLogging()
      Enable logging by instantiating the underlying Log objects.
      void error(java.lang.Object message)
      Log a message with error log level.
      void error(java.lang.Object message, java.lang.Throwable ex)
      Log an error with error log level.
      void fatal(java.lang.Object message)
      Log a message with fatal log level.
      void fatal(java.lang.Object message, java.lang.Throwable ex)
      Log an error with fatal log level.
      void info(java.lang.Object message)
      Log a message with info log level.
      void info(java.lang.Object message, java.lang.Throwable ex)
      Log an error with info log level.
      boolean isDebugEnabled()
      Determine whether debug logging is currently enabled.
      boolean isErrorEnabled()
      Determine whether error logging is currently enabled.
      boolean isFatalEnabled()
      Determine whether fatal logging is currently enabled.
      boolean isInfoEnabled()
      Determine whether info logging is currently enabled.
      boolean isTraceEnabled()
      Determine whether trace logging is currently enabled.
      boolean isWarningEnabled()
      Determine whether warn logging is currently enabled.
      void message(LogLevel level, java.lang.Object message)
      Log a message at a specified log level.
      void message(LogLevel level, java.lang.Object message, java.lang.Throwable ex)
      Log a message at a specified log level.
      void trace(java.lang.Object message)
      Log a message with trace log level.
      void trace(java.lang.Object message, java.lang.Throwable ex)
      Log an error with trace log level.
      void warn(java.lang.Object message)
      Log a message with warn log level.
      void warn(java.lang.Object message, java.lang.Throwable ex)
      Log an error with warn log level.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • LEVEL_DEBUG

        public static LogLevel LEVEL_DEBUG
        Log level constant for debug messages. Defined here for backward compatibility.
        See Also:
        LogLevel.DEBUG

      • LEVEL_ERROR

        public static LogLevel LEVEL_ERROR
        Log level constant for error messages. Defined here for backward compatibility.
        See Also:
        LogLevel.ERROR

      • LEVEL_FATAL

        public static LogLevel LEVEL_FATAL
        Log level constant for fatal-error messages. Defined here for backward compatibility.
        See Also:
        LogLevel.FATAL

      • LEVEL_INFO

        public static LogLevel LEVEL_INFO
        Log level constant for informational messages. Defined here for backward compatibility.
        See Also:
        LogLevel.INFO

      • LEVEL_TRACE

        public static LogLevel LEVEL_TRACE
        Log level constant for trace messages. Defined here for backward compatibility.
        See Also:
        LogLevel.TRACE

      • LEVEL_WARNING

        public static LogLevel LEVEL_WARNING
        Log level constant for warning messages. Defined here for backward compatibility.
        See Also:
        LogLevel.WARNING

    • Constructor Detail

      • Logger

        public Logger(java.lang.String className)
        Construct a new Logger object
        Parameters:
        className - the class name to associate with the object

      • Logger

        public Logger(java.lang.Class cls)
        Construct a new Logger object
        Parameters:
        cls - the class whose name should be associated with the object

    • Method Detail

      • enableLogging

        public static void enableLogging()
                          throws java.lang.UnsupportedOperationException
        Enable logging by instantiating the underlying Log objects. Enables logging for all instantiated Logger objects, and ensures that any subsequently instantiated Logger objects will be enabled.
        Throws:
        java.lang.UnsupportedOperationException - could not find Commons Logging API

      • debug

        public void debug(java.lang.Object message)
        Log a message with debug log level.
        Parameters:
        message - The message to convert to a string and log

      • debug

        public void debug(java.lang.Object message,
                  java.lang.Throwable ex)
        Log an error with debug log level.
        Parameters:
        message - The message to convert to a string and log
        ex - The exception to log with the message

      • error

        public void error(java.lang.Object message)
        Log a message with error log level.
        Parameters:
        message - The message to convert to a string and log

      • error

        public void error(java.lang.Object message,
                  java.lang.Throwable ex)
        Log an error with error log level.
        Parameters:
        message - The message to convert to a string and log
        ex - The exception to log with the message

      • fatal

        public void fatal(java.lang.Object message)
        Log a message with fatal log level.
        Parameters:
        message - The message to convert to a string and log

      • fatal

        public void fatal(java.lang.Object message,
                  java.lang.Throwable ex)
        Log an error with fatal log level.
        Parameters:
        message - The message to convert to a string and log
        ex - The exception to log with the message

      • info

        public void info(java.lang.Object message)
        Log a message with info log level.
        Parameters:
        message - The message to convert to a string and log

      • info

        public void info(java.lang.Object message,
                 java.lang.Throwable ex)
        Log an error with info log level.
        Parameters:
        message - The message to convert to a string and log
        ex - The exception to log with the message

      • message

        public void message(LogLevel level,
                    java.lang.Object message)
        Log a message at a specified log level.
        Parameters:
        level - the log level
        message - the message

      • message

        public void message(LogLevel level,
                    java.lang.Object message,
                    java.lang.Throwable ex)
        Log a message at a specified log level.
        Parameters:
        level - the log level
        message - the message
        ex - The exception to log with the message

      • trace

        public void trace(java.lang.Object message)
        Log a message with trace log level.
        Parameters:
        message - The message to convert to a string and log

      • trace

        public void trace(java.lang.Object message,
                  java.lang.Throwable ex)
        Log an error with trace log level.
        Parameters:
        message - The message to convert to a string and log
        ex - The exception to log with the message

      • warn

        public void warn(java.lang.Object message)
        Log a message with warn log level.
        Parameters:
        message - The message to convert to a string and log

      • warn

        public void warn(java.lang.Object message,
                 java.lang.Throwable ex)
        Log an error with warn log level.
        Parameters:
        message - The message to convert to a string and log
        ex - The exception to log with the message

      • isDebugEnabled

        public boolean isDebugEnabled()
        Determine whether debug logging is currently enabled.
        Returns:
        true if debug logging is enabled, false otherwise

      • isErrorEnabled

        public boolean isErrorEnabled()
        Determine whether error logging is currently enabled.
        Returns:
        true if error logging is enabled, false otherwise

      • isFatalEnabled

        public boolean isFatalEnabled()
        Determine whether fatal logging is currently enabled.
        Returns:
        true if fatal logging is enabled, false otherwise

      • isInfoEnabled

        public boolean isInfoEnabled()
        Determine whether info logging is currently enabled.
        Returns:
        true if info logging is enabled, false otherwise

      • isTraceEnabled

        public boolean isTraceEnabled()
        Determine whether trace logging is currently enabled.
        Returns:
        true if trace logging is enabled, false otherwise

      • isWarningEnabled

        public boolean isWarningEnabled()
        Determine whether warn logging is currently enabled.
        Returns:
        true if warn logging is enabled, false otherwise
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