Logger

java.lang.Object
- org.clapper.util.logging.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:

Mappings
`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

Field Summary

Fields
Modifier and Type	Field and Description
`static LogLevel`	`LEVEL_DEBUG` Log level constant for debug messages.
`static LogLevel`	`LEVEL_ERROR` Log level constant for error messages.
`static LogLevel`	`LEVEL_FATAL` Log level constant for fatal-error messages.
`static LogLevel`	`LEVEL_INFO` Log level constant for informational messages.
`static LogLevel`	`LEVEL_TRACE` Log level constant for trace messages.
`static LogLevel`	`LEVEL_WARNING` Log level constant for warning messages.

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

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
clone, equals, finalize, 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

Class Logger

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LEVEL_DEBUG

LEVEL_ERROR

LEVEL_FATAL

LEVEL_INFO

LEVEL_TRACE

LEVEL_WARNING

Constructor Detail

Logger

Logger

Method Detail

enableLogging

debug

debug

error

error

fatal

fatal

info

info

message

message

trace

trace

warn

warn

isDebugEnabled

isErrorEnabled

isFatalEnabled

isInfoEnabled

isTraceEnabled

isWarningEnabled