Class Logger

java.lang.Object

org.apache.felix.framework.Logger

All Implemented Interfaces:

EventListener, ServiceListener

public class Logger
extends Object
implements ServiceListener

This class mimics the standard OSGi LogService interface. An instance of this class is used by the framework for all logging. By default this class logs messages to standard out. The log level can be set to control the amount of logging performed, where a higher number results in more logging. A log level of zero turns off logging completely.

The log levels match those specified in the OSGi Log Service (i.e., 1 = error, 2 = warning, 3 = information, and 4 = debug). The default value is 1.

This class also uses the System Bundle's context to track log services and will use the highest ranking log service, if present, as a back end instead of printing to standard out. The class uses reflection to invoking the log service's method to avoid a dependency on the log interface.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	LOG_DEBUG
static final int	LOG_ERROR
static final int	LOG_INFO
static final int	LOG_WARNING
private static final int	LOGGER_METHOD_IDX
private static final int	LOGGER_OBJECT_IDX
private BundleContext	m_context
private Object[]	m_logger
private int	m_logLevel
private ServiceReference	m_logRef

Constructor Summary

Constructors

Constructor	Description
Logger()

Method Summary

Modifier and Type	Method	Description
private void	_log(Bundle bundle, ServiceReference sr, int level, String msg, Throwable throwable)
private void	_logReflectively(Object[] logger, ServiceReference sr, int level, String msg, Throwable throwable)
protected void	doLog(Bundle bundle, ServiceReference sr, int level, String msg, Throwable throwable)
final int	getLogLevel()
final void	log(int level, String msg)
final void	log(int level, String msg, Throwable throwable)
final void	log(Bundle bundle, int level, String msg)
final void	log(Bundle bundle, int level, String msg, Throwable throwable)
final void	log(ServiceReference sr, int level, String msg)
final void	log(ServiceReference sr, int level, String msg, Throwable throwable)
final void	serviceChanged(ServiceEvent event)	This method implements the callback for the ServiceListener interface.
private void	setLogger(Object logObj)	This method sets the new log service object.
final void	setLogLevel(int i)
protected void	setSystemBundleContext(BundleContext context)
private void	startListeningForLogService()	This method is called when the system bundle context is set; it simply adds a service listener so that the system bundle can track log services to be used as the back end of the logging mechanism.

Methods inherited from class Object

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

Field Details

LOG_ERROR

public static final int LOG_ERROR

See Also:

• Constant Field Values

LOG_WARNING

public static final int LOG_WARNING

See Also:

• Constant Field Values

LOG_INFO

public static final int LOG_INFO

See Also:

• Constant Field Values

LOG_DEBUG

public static final int LOG_DEBUG

See Also:

• Constant Field Values

m_logLevel

private int m_logLevel

m_context

private BundleContext m_context

LOGGER_OBJECT_IDX

private static final int LOGGER_OBJECT_IDX

See Also:

• Constant Field Values

LOGGER_METHOD_IDX

private static final int LOGGER_METHOD_IDX

See Also:

• Constant Field Values

m_logRef

private ServiceReference m_logRef

m_logger

private Object[] m_logger

Constructor Details

Logger

public Logger()

Method Details

setLogLevel

public final void setLogLevel(int i)

getLogLevel

public final int getLogLevel()

setSystemBundleContext

protected void setSystemBundleContext(BundleContext context)

log

public final void log(int level,
 String msg)

log

public final void log(int level,
 String msg,
 Throwable throwable)

log

public final void log(ServiceReference sr,
 int level,
 String msg)

log

public final void log(ServiceReference sr,
 int level,
 String msg,
 Throwable throwable)

log

public final void log(Bundle bundle,
 int level,
 String msg)

log

public final void log(Bundle bundle,
 int level,
 String msg,
 Throwable throwable)

doLog

protected void doLog(Bundle bundle,
 ServiceReference sr,
 int level,
 String msg,
 Throwable throwable)

_log

private void _log(Bundle bundle,
 ServiceReference sr,
 int level,
 String msg,
 Throwable throwable)

_logReflectively

private void _logReflectively(Object[] logger,
 ServiceReference sr,
 int level,
 String msg,
 Throwable throwable)

startListeningForLogService

private void startListeningForLogService()

This method is called when the system bundle context is set; it simply adds a service listener so that the system bundle can track log services to be used as the back end of the logging mechanism. It also attempts to get an existing log service, if present, but in general there will never be a log service present since the system bundle is started before every other bundle.

serviceChanged

public final void serviceChanged(ServiceEvent event)

This method implements the callback for the ServiceListener interface. It is public as a byproduct of implementing the interface and should not be called directly. This method tracks run-time changes to log service availability. If the log service being used by the framework's logging mechanism goes away, then this will try to find an alternative. If a higher ranking log service is registered, then this will switch to the higher ranking log service.

Specified by:

serviceChanged in interface ServiceListener

Parameters:

event - The ServiceEvent object.

setLogger

private void setLogger(Object logObj)

This method sets the new log service object. It also caches the method to invoke. The service object and method are stored in array to optimistically eliminate the need to locking when logging.