com.antelmann.util.logging
Class Logger

java.lang.Object
  com.antelmann.util.logging.Logger

All Implemented Interfaces:

Enabled, Filter<LogEntry>, Forgeable<Logger>, QueryMechanism

public class Logger
extends Object
implements Filter<LogEntry>, Forgeable<Logger>, QueryMechanism, Enabled

Logger somewhat leans on the functionality of the java.util.logging functionality of J2SE 1.4, but it's not quite the same (and was implemented before J2SE 1.4).

In addition to the J2SE functionality, it provides the full stack trace for the log. Whether or not the logging here is written synchronously or asynchronously, is left to the implementation for each LogWriter that is used with the Logger.

All logging methods may throw LogException - propagated from the LogWriter objects contained in the logger to the calling thread. The writing to the different LogWriters is always performed sequentially in the order the LogWriters were added to the Logger.

It is recommended to always use a log method with the origin parameter and pass the 'this' argument from the calling function; this will provide useful additional information for the log.

Author:

Holger Antelmann

See Also:

LogWriter, LoggerCache, LogEntry, LogException

Field Summary

Fields inherited from interface com.antelmann.util.Filter

EXCLUDE_ALL_FILTER, INCLUDE_ALL_FILTER

Fields inherited from interface com.antelmann.util.Enabled

FILTER

Constructor Summary

Logger()
creates an empty Logger that does not write to any log yet

Logger(Logger logger)
uses the configuration from the given logger (including writers and filter)

Logger(LogWriter... writer)

Method Summary

boolean	accept(LogEntry entry) returns true only if the given entry will be logged by this logger and thus propagated to its handlers
boolean	addWriter(LogWriter writer) adds the given handler to the list of handlers this Logger writes to
void	addWritersFromLogger(Logger logger) adds all LogWriter handler from the given logger
void	clearLast() sets the last logged entry to null
void	closeAllWriters() convenience method: attempts to close all embedded writers - if applicable
boolean	containsWriter(LogWriter writer)
LogExceptionHandler	getExceptionHandler() if the LogExceptionHandler is null (which it is by default), any LogException during logging is propagated to the calling application.
Filter<? super LogEntry>	getFilter() returns null by default
LogEntry	getLast() returns the last entry logged with this logger (while enabled and filter passed).
LogWriter[]	getWriters()
void	ignoreLogExceptions() sets a LogExceptionHandler that simply ignores any given LogException, so no Exception will be propagated to the calling application if logging fails.
boolean	includesStack() returns true if a stack trace is produced when a Logger method creates a LogEntry (false by default)
boolean	isEnabled() the logger only logs if the return value is true (which it is by default)
boolean	isResolveOriginIfMissing()
void	log(Level level, String message, long time, String sourceClass, String sourceString, Throwable thrown, String threadName, StackTraceElement[] stack, Object[] parameters)
void	log(Level level, String message, Object... parameters)
void	log(LogEntry entry) logs the entry by writing to the writers after checking whether the logger is enabled and the filter (if available) accepts the entry.
void	log(Object origin, Level level, String message, Object... parameters)
void	log(Object origin, Level level, Throwable thrown, String message, Object... parameters)
void	log(Object origin, String message, Object... parameters)
void	log(Object origin, Throwable thrown)
void	log(String message, Object... parameters)
void	log(Throwable thrown)
void	log(Throwable thrown, String message, Object... parameters)
<T> T	query(Class<T> requiredReturnType, Object context) returns the first embedded LogWriter that is also an instance of the given requiredReturnType or null
void	removeAllWriters()
boolean	removeWriter(LogWriter writer) removes the given writer from the list of log writers
void	setAllFrom(Logger logger) copies the properties of the given object and applies them to this instance, so that its behavior in regards to the given object can be matched to the extend that the implementing class supports that behavior.
void	setEnabled(boolean flag) allows to enable/disable this instance
void	setExceptionHandler(LogExceptionHandler handler)
void	setFilter(Filter<? super LogEntry> filter)
void	setIncludeStack(boolean on)
void	setResolveOriginIfMissing(boolean flag)

Methods inherited from class java.lang.Object

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

Constructor Detail

Logger

public Logger()

creates an empty Logger that does not write to any log yet

Logger

public Logger(LogWriter... writer)

Logger

public Logger(Logger logger)

uses the configuration from the given logger (including writers and filter)

Method Detail

query

public <T> T query(Class<T> requiredReturnType,
                   Object context)
        throws IllegalArgumentException

returns the first embedded LogWriter that is also an instance of the given requiredReturnType or null

Specified by:

query in interface QueryMechanism

Type Parameters:

T - the required return type

Parameters:

requiredReturnType - specifies the return type that is needed for this operation; if Object.class is given, any returned object is admissible

context - provides a context parameter for which the desired instance is to be returned. Often (if no other meaningful context is required or applicable), it makes sense to pass a reference to the calling object source; null may also be allowed

Returns:

an instance of the required return type that matches the given context; null may be returned if no instance is available for the given context

Throws:

IllegalArgumentException - if the given requiredReturnType doesn't implement LogWriter

setAllFrom

public void setAllFrom(Logger logger)

Description copied from interface: Forgeable

copies the properties of the given object and applies them to this instance, so that its behavior in regards to the given object can be matched to the extend that the implementing class supports that behavior.

Specified by:

setAllFrom in interface Forgeable<Logger>

Parameters:

logger - the object whose behavior is to be copied to this instance

getWriters

public LogWriter[] getWriters()

addWritersFromLogger

public void addWritersFromLogger(Logger logger)

adds all LogWriter handler from the given logger

includesStack

public boolean includesStack()

returns true if a stack trace is produced when a Logger method creates a LogEntry (false by default)

setIncludeStack

public void setIncludeStack(boolean on)

isResolveOriginIfMissing

public boolean isResolveOriginIfMissing()

setResolveOriginIfMissing

public void setResolveOriginIfMissing(boolean flag)

addWriter

public boolean addWriter(LogWriter writer)

adds the given handler to the list of handlers this Logger writes to

Returns:

true if the set did not already contain the writer

removeWriter

public boolean removeWriter(LogWriter writer)

removes the given writer from the list of log writers

Returns:

true if the set contained the handler

containsWriter

public boolean containsWriter(LogWriter writer)

removeAllWriters

public void removeAllWriters()

closeAllWriters

public void closeAllWriters()

convenience method: attempts to close all embedded writers - if applicable

log

public void log(String message,
                Object... parameters)
         throws LogException

Throws:

LogException

log

public void log(Level level,
                String message,
                Object... parameters)
         throws LogException

Throws:

LogException

log

public void log(Throwable thrown)
         throws LogException

Throws:

LogException

log

public void log(Throwable thrown,
                String message,
                Object... parameters)
         throws LogException

Throws:

LogException

log

public void log(Object origin,
                String message,
                Object... parameters)
         throws LogException

Throws:

LogException

log

public void log(Object origin,
                Level level,
                String message,
                Object... parameters)
         throws LogException

Throws:

LogException

log

public void log(Object origin,
                Throwable thrown)
         throws LogException

Throws:

LogException

log

public void log(Object origin,
                Level level,
                Throwable thrown,
                String message,
                Object... parameters)
         throws LogException

Throws:

LogException

log

public void log(Level level,
                String message,
                long time,
                String sourceClass,
                String sourceString,
                Throwable thrown,
                String threadName,
                StackTraceElement[] stack,
                Object[] parameters)
         throws LogException

Throws:

LogException

isEnabled

public boolean isEnabled()

the logger only logs if the return value is true (which it is by default)

Specified by:

isEnabled in interface Enabled

setEnabled

public void setEnabled(boolean flag)

Description copied from interface: Enabled

allows to enable/disable this instance

Specified by:

setEnabled in interface Enabled

getFilter

public Filter<? super LogEntry> getFilter()

returns null by default

accept

public boolean accept(LogEntry entry)

returns true only if the given entry will be logged by this logger and thus propagated to its handlers

Specified by:

accept in interface Filter<LogEntry>

See Also:

getWriters()

setFilter

public void setFilter(Filter<? super LogEntry> filter)

setExceptionHandler

public void setExceptionHandler(LogExceptionHandler handler)

getExceptionHandler

public LogExceptionHandler getExceptionHandler()

if the LogExceptionHandler is null (which it is by default), any LogException during logging is propagated to the calling application.

See Also:

ignoreLogExceptions()

ignoreLogExceptions

public void ignoreLogExceptions()

sets a LogExceptionHandler that simply ignores any given LogException, so no Exception will be propagated to the calling application if logging fails. To reverse the effect of calling this method, simply set the LogExceptionHandler back to a null value - or use any other customized LogExceptionHandler.

See Also:

setExceptionHandler(LogExceptionHandler), LogExceptionHandler.EXCEPTION_IGNORER

log

public void log(LogEntry entry)
         throws LogException

logs the entry by writing to the writers after checking whether the logger is enabled and the filter (if available) accepts the entry. This is the method that ultimately called by all other logging methods. Only after all writers have been called, the last logging entry is set, i.e. if a writer would call getLast() while writing the entry, a previous entry would be returned.

Throws:

LogException - if a LogWriter throws a LogException during logging. The exception handling can be controlled by setting an LogExceptionHandler. If no LogExceptionHandler is configured, the Exception is simply propagated to the calling method.

See Also:

getFilter(), isEnabled(), ignoreLogExceptions(), setExceptionHandler(LogExceptionHandler)

getLast

public LogEntry getLast()

returns the last entry logged with this logger (while enabled and filter passed).

See Also:

LoggerCache

clearLast

public void clearLast()

sets the last logged entry to null