org.apache.logging.log4j
Interface LevelLogger

public interface LevelLogger

This is the central interface in the log4j package. Most logging operations, except configuration, are done through this interface.

The canonical way to obtain a Logger for a class is through LogManager.getLogger(). Typically, each class gets its own Logger named after its fully qualified class name (the default Logger name when obtained through the LogManager.getLogger() method). Thus, the simplest way to use this would be like so:

 public class MyClass {
     private static final Logger LOGGER = LogManager.getLogger();
     // ...
 }
 

For ease of filtering, searching, sorting, etc., it is generally a good idea to create Loggers for each class rather than sharing Loggers. Instead, Markers should be used for shared, filterable identification.

For service provider implementations, it is recommended to extend the AbstractLogger class rather than implementing this interface directly.

Method Summary

void	catching(Throwable t) Logs an exception or error that has been caught.
void	entry() Logs entry to a method.
void	entry(Object... params) Logs entry to a method along with its parameters.
void	exit() Logs exit from a method.
<R> R	exit(R result) Logs exiting from a method with the result.
Level	getLevel() Gets the Level associated with the Logger.
MessageFactory	getMessageFactory() Gets the message factory used to convert message Objects and Strings into actual log Messages.
String	getName() Gets the logger name.
boolean	isDebugEnabled() Checks whether this Logger is enabled for the DEBUG Level.
boolean	isDebugEnabled(Marker marker) Checks whether this Logger is enabled for the DEBUG Level.
boolean	isEnabled(Level level) Checks whether this Logger is enabled for the the given Level.
boolean	isEnabled(Marker marker) Checks whether this logger is enabled at the specified level and an optional Marker.
boolean	isErrorEnabled() Checks whether this Logger is enabled for the ERROR Level.
boolean	isErrorEnabled(Marker marker) Checks whether this Logger is enabled for the ERROR Level.
boolean	isFatalEnabled() Checks whether this Logger is enabled for the FATAL Level.
boolean	isFatalEnabled(Marker marker) Checks whether this Logger is enabled for the FATAL Level.
boolean	isInfoEnabled() Checks whether this Logger is enabled for the INFO Level.
boolean	isInfoEnabled(Marker marker) Checks whether this Logger is enabled for the INFO Level.
boolean	isTraceEnabled() Checks whether this Logger is enabled for the TRACE level.
boolean	isTraceEnabled(Marker marker) Checks whether this Logger is enabled for the TRACE level.
boolean	isWarnEnabled() Checks whether this Logger is enabled for the WARN Level.
boolean	isWarnEnabled(Marker marker) Checks whether this Logger is enabled for the WARN Level.
void	log(Marker marker, Message msg) Logs a message with the specific Marker at the given level.
void	log(Marker marker, Message msg, Throwable t) Logs a message with the specific Marker at the given level.
void	log(Marker marker, Object message) Logs a message object with the given level.
void	log(Marker marker, Object message, Throwable t) Logs a message at the given level including the stack trace of the Throwable t passed as parameter.
void	log(Marker marker, String message) Logs a message object with the given level.
void	log(Marker marker, String message, Object... params) Logs a message with parameters at the given level.
void	log(Marker marker, String message, Throwable t) Logs a message at the given level including the stack trace of the Throwable t passed as parameter.
void	log(Message msg) Logs a message with the specific Marker at the given level.
void	log(Message msg, Throwable t) Logs a message with the specific Marker at the given level.
void	log(Object message) Logs a message object with the given level.
void	log(Object message, Throwable t) Logs a message at the given level including the stack trace of the Throwable t passed as parameter.
void	log(String message) Logs a message object with the given level.
void	log(String message, Object... params) Logs a message with parameters at the given level.
void	log(String message, Throwable t) Logs a message at the given level including the stack trace of the Throwable t passed as parameter.
void	printf(Marker marker, String format, Object... params) Logs a formatted message using the specified format string and arguments.
void	printf(String format, Object... params) Logs a formatted message using the specified format string and arguments.
<T extends Throwable> T	throwing(T t) Logs an exception or error to be thrown.

Method Detail

catching

void catching(Throwable t)

Logs an exception or error that has been caught. Normally, one may wish to provide additional information with an exception while logging it; in these cases, one would not use this method. In other cases where simply logging the fact that an exception was swallowed somewhere (e.g., at the top of the stack trace in a main() method), this method is ideal for it.

Parameters:

t - The Throwable.

entry

void entry()

Logs entry to a method. Used when the method in question has no parameters or when the parameters should not be logged.

entry

void entry(Object... params)

Logs entry to a method along with its parameters. For example,

 public void doSomething(String foo, int bar) {
     LOGGER.entry(foo, bar);
     // do something
 }
 

The use of methods such as this are more effective when combined with aspect-oriented programming or other bytecode manipulation tools. It can be rather tedious (and messy) to use this type of method manually.

Parameters:

params - The parameters to the method. TODO Use of varargs results in array creation which can be a substantial portion of no-op case. LogMF/LogSF provides several overrides to avoid vararg except in edge cases. (RG) LogMF and LogSF implement these in LogXF which calls logger.callAppenders. callAppenders is part of the implementation and cannot be used by the API. Adding more methods here and in AbstractLogger is sufficient.

exit

void exit()

Logs exit from a method. Used for methods that do not return anything.

exit

<R> R exit(R result)

Logs exiting from a method with the result. This may be coded as:

 return LOGGER.exit(myResult);
 

Type Parameters:

R - The type of the parameter and object being returned.

Parameters:

result - The result being returned from the method call.

Returns:

the result.

getLevel

Level getLevel()

Gets the Level associated with the Logger.

Returns:

the Level associate with the Logger.

getMessageFactory

MessageFactory getMessageFactory()

Gets the message factory used to convert message Objects and Strings into actual log Messages.

Returns:

the message factory.

getName

String getName()

Gets the logger name.

Returns:

the logger name.

isDebugEnabled

boolean isDebugEnabled()

Checks whether this Logger is enabled for the DEBUG Level.

Returns:

boolean - true if this Logger is enabled for level DEBUG, false otherwise.

isDebugEnabled

boolean isDebugEnabled(Marker marker)

Checks whether this Logger is enabled for the DEBUG Level.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level DEBUG, false otherwise.

isEnabled

boolean isEnabled(Level level)

Checks whether this Logger is enabled for the the given Level.

Note that passing in OFF always returns true.

Returns:

boolean - true if this Logger is enabled for level, false otherwise.

isEnabled

boolean isEnabled(Marker marker)

Checks whether this logger is enabled at the specified level and an optional Marker.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level WARN, false otherwise.

isErrorEnabled

boolean isErrorEnabled()

Checks whether this Logger is enabled for the ERROR Level.

Returns:

boolean - true if this Logger is enabled for level ERROR, false otherwise.

isErrorEnabled

boolean isErrorEnabled(Marker marker)

Checks whether this Logger is enabled for the ERROR Level.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level ERROR, false otherwise.

isFatalEnabled

boolean isFatalEnabled()

Checks whether this Logger is enabled for the FATAL Level.

Returns:

boolean - true if this Logger is enabled for level FATAL, false otherwise.

isFatalEnabled

boolean isFatalEnabled(Marker marker)

Checks whether this Logger is enabled for the FATAL Level.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level FATAL, false otherwise.

isInfoEnabled

boolean isInfoEnabled()

Checks whether this Logger is enabled for the INFO Level.

Returns:

boolean - true if this Logger is enabled for level INFO, false otherwise.

isInfoEnabled

boolean isInfoEnabled(Marker marker)

Checks whether this Logger is enabled for the INFO Level.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level INFO, false otherwise.

isTraceEnabled

boolean isTraceEnabled()

Checks whether this Logger is enabled for the TRACE level.

Returns:

boolean - true if this Logger is enabled for level TRACE, false otherwise.

isTraceEnabled

boolean isTraceEnabled(Marker marker)

Checks whether this Logger is enabled for the TRACE level.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level TRACE, false otherwise.

isWarnEnabled

boolean isWarnEnabled()

Checks whether this Logger is enabled for the WARN Level.

Returns:

boolean - true if this Logger is enabled for level WARN, false otherwise.

isWarnEnabled

boolean isWarnEnabled(Marker marker)

Checks whether this Logger is enabled for the WARN Level.

Parameters:

marker - The marker data specific to this log statement.

Returns:

boolean - true if this Logger is enabled for level WARN, false otherwise.

log

void log(Marker marker,
         Message msg)

Logs a message with the specific Marker at the given level.

Parameters:

marker - the marker data specific to this log statement

msg - the message string to be logged

log

void log(Marker marker,
         Message msg,
         Throwable t)

Logs a message with the specific Marker at the given level.

Parameters:

marker - the marker data specific to this log statement

msg - the message string to be logged

t - A Throwable or null.

log

void log(Marker marker,
         Object message)

Logs a message object with the given level.

Parameters:

marker - the marker data specific to this log statement

message - the message object to log.

log

void log(Marker marker,
         Object message,
         Throwable t)

Logs a message at the given level including the stack trace of the Throwable t passed as parameter.

Parameters:

marker - the marker data specific to this log statement

message - the message to log.

t - the exception to log, including its stack trace.

log

void log(Marker marker,
         String message)

Logs a message object with the given level.

Parameters:

marker - the marker data specific to this log statement

message - the message object to log.

log

void log(Marker marker,
         String message,
         Object... params)

Logs a message with parameters at the given level.

Parameters:

marker - the marker data specific to this log statement

message - the message to log; the format depends on the message factory.

params - parameters to the message.

See Also:

getMessageFactory()

log

void log(Marker marker,
         String message,
         Throwable t)

Logs a message at the given level including the stack trace of the Throwable t passed as parameter.

Parameters:

marker - the marker data specific to this log statement

message - the message to log.

t - the exception to log, including its stack trace.

log

void log(Message msg)

Logs a message with the specific Marker at the given level.

Parameters:

msg - the message string to be logged

log

void log(Message msg,
         Throwable t)

Logs a message with the specific Marker at the given level.

Parameters:

msg - the message string to be logged

t - A Throwable or null.

log

void log(Object message)

Logs a message object with the given level.

Parameters:

message - the message object to log.

log

void log(Object message,
         Throwable t)

Logs a message at the given level including the stack trace of the Throwable t passed as parameter.

Parameters:

message - the message to log.

t - the exception to log, including its stack trace.

log

void log(String message)

Logs a message object with the given level.

Parameters:

message - the message string to log.

log

void log(String message,
         Object... params)

Logs a message with parameters at the given level.

Parameters:

message - the message to log; the format depends on the message factory.

params - parameters to the message.

See Also:

getMessageFactory()

log

void log(String message,
         Throwable t)

Logs a message at the given level including the stack trace of the Throwable t passed as parameter.

Parameters:

message - the message to log.

t - the exception to log, including its stack trace.

printf

void printf(Marker marker,
            String format,
            Object... params)

Logs a formatted message using the specified format string and arguments.

Parameters:

marker - the marker data specific to this log statement.

format - The format String.

params - Arguments specified by the format.

printf

void printf(String format,
            Object... params)

Logs a formatted message using the specified format string and arguments.

Parameters:

format - The format String.

params - Arguments specified by the format.

throwing

<T extends Throwable> T throwing(T t)

Logs an exception or error to be thrown. This may be coded as:

 throw logger.throwing(myException);
 

Type Parameters:

T - the Throwable type.

Parameters:

t - The Throwable.

Returns:

the Throwable.