Apache Log4j JUL Adapter 2.22.0 · org.apache.logging.log4j.jul.Log4jBridgeHandler

Bridge from JUL to log4j2.
This is an alternative to log4j.jul.LogManager (running as complete JUL replacement), especially useful for webapps running on a container for which the LogManager cannot or should not be used.

Installation/usage:

Declaratively inside JUL's logging.properties:
handlers = org.apache.logging.log4j.jul.Log4jBridgeHandler
(and typically also: org.apache.logging.log4j.jul.Log4jBridgeHandler.propagateLevels = true )
Note: in a webapp running on Tomcat, you may create a WEB-INF/classes/logging.properties file to configure JUL for this webapp only: configured handlers and log levels affect your webapp only! This file is then the complete JUL configuration, so JUL's defaults (e.g. log level INFO) apply for stuff not explicitly defined therein.
Programmatically by calling install() method, e.g. inside ServletContextListener static-class-init. or contextInitialized()

Configuration (in JUL's logging.properties):

Log4jBridgeHandler.suffixToAppend
String, suffix to append to JUL logger names, to easily recognize bridged log messages. A dot "." is automatically prepended, so configuration for the basis logger is used
Example: Log4jBridgeHandler.suffixToAppend = _JUL
Useful, for example, if you use JSF because it logs exceptions and throws them afterwards; you can easily recognize the duplicates with this (or concentrate on the non-JUL-logs).
Log4jBridgeHandler.propagateLevels boolean, "true" to automatically propagate log4j log levels to JUL.
Log4jBridgeHandler.sysoutDebug boolean, perform some (developer) debug output to sysout

Log levels are translated with LevelTranslator, see also log4j doc.

Restrictions:

Manually given source/location info in JUL (e.g. entering(), exiting(), throwing(), logp(), logrb() ) will NOT be considered, i.e. gets lost in log4j logging.
Log levels of JUL have to be adjusted according to log4j log levels: Either by using "propagateLevels" (preferred), or manually by specifying them explicitly, i.e. logging.properties and log4j2.xml have some redundancies.
Only JUL log events that are allowed according to the JUL log level get to this handler and thus to log4j. This is only relevant and important if you NOT use "propagateLevels". If you set .level = SEVERE only error logs will be seen by this handler and thus log4j - even if the corresponding log4j log level is ALL.
On the other side, you should NOT set .level = FINER or FINEST if the log4j level is higher. In this case a lot of JUL log events would be generated, sent via this bridge to log4j and thrown away by the latter.
Note: JUL's default log level (i.e. none specified in logger.properties) is INFO.

(Credits: idea and concept originate from org.slf4j.bridge.SLF4JBridgeHandler; level propagation idea originates from logback/LevelChangePropagator; but no source code has been copied)

Field Summary

Modifier and Type	Field and Description
private boolean	doDebugOutput
private static final String	FQCN
private volatile boolean	installAsLevelPropagator
private static final Formatter	julFormatter
private Set<Logger>	julLoggerRefs Save "hard" references to configured JUL loggers.
private String	julSuffixToAppend
private static final Logger	SLOGGER
private static final String	UNKNOWN_LOGGER_NAME

Constructor Summary

Access	Constructor and Description
public	Log4jBridgeHandler() Initialize this handler by reading out JUL configuration.
public	Log4jBridgeHandler(boolean debugOutput, String suffixToAppend, boolean propagateLevels) Initialize this handler with given configuration.

Method Summary

Modifier and Type	Method and Description
public void	close() Implements abstract java.util.logging.Handler.close. Close the `Handler` and free all associated resources.
public void	flush() Implements abstract java.util.logging.Handler.flush. Flush any buffered output.
private static Logger	getJulRootLogger()
private Logger	getLog4jLogger(final LogRecord record) Return the log4j-Logger instance that will be used for logging.
protected void	init(boolean debugOutput, String suffixToAppend, boolean propagateLevels) Perform init.
public static void	install(boolean true to remove all other installed handlers on JUL root level removeHandlersForRootLogger, String suffixToAppend, boolean propagateLevels) Adds a new Log4jBridgeHandler instance to JUL's root logger.
private void	propagateLogLevels(final org.apache.logging.log4j.core.config.Configuration config) Perform developer tests?
public void	propertyChange(final PropertyChangeEvent A PropertyChangeEvent object describing the event source and the property that has changed. evt) Implements java.beans.PropertyChangeListener.propertyChange. This method gets called when a bound property is changed.
public void	publish(final LogRecord description of the log event. A null record is silently ignored and is not published record) Implements abstract java.util.logging.Handler.publish. Publish a `LogRecord`.

Inherited from java.util.logging.Handler:: getEncoding getErrorManager getFilter getFormatter getLevel isLoggable reportError setEncoding setErrorManager setFilter setFormatter setLevel

Field Detail

doDebugOutput	back to summary
private boolean doDebugOutput

FQCN	back to summary
private static final String FQCN

installAsLevelPropagator	back to summary
private volatile boolean installAsLevelPropagator

julFormatter	back to summary
private static final Formatter julFormatter

julLoggerRefs	back to summary
private Set<Logger> julLoggerRefs Save "hard" references to configured JUL loggers. (is lazy init.)

julSuffixToAppend	back to summary
private String julSuffixToAppend

SLOGGER	back to summary
private static final Logger SLOGGER

UNKNOWN_LOGGER_NAME	back to summary
private static final String UNKNOWN_LOGGER_NAME

Constructor Detail

Log4jBridgeHandler	back to summary
public Log4jBridgeHandler() Initialize this handler by reading out JUL configuration.

Log4jBridgeHandler	back to summary
public Log4jBridgeHandler(boolean debugOutput, String suffixToAppend, boolean propagateLevels) Initialize this handler with given configuration.

Method Detail

close back to summary

close	back to summary
public void close() Implements abstract java.util.logging.Handler.close. Doc from java.util.logging.Handler.close. Close the `Handler` and free all associated resources. The close method will perform a `flush` and then close the `Handler`. After close has been called this `Handler` should no longer be used. Method calls may either be silently ignored or may throw runtime exceptions. Annotations @Override

public void close()

Implements abstract java.util.logging.Handler.close.

Doc from java.util.logging.Handler.close.

Close the Handler and free all associated resources.

The close method will perform a flush and then close the Handler. After close has been called this Handler should no longer be used. Method calls may either be silently ignored or may throw runtime exceptions.

Annotations

@Override

flush	back to summary
public void flush() Implements abstract java.util.logging.Handler.flush. Doc from java.util.logging.Handler.flush. Flush any buffered output. Annotations @Override

flush

back to summary

public void flush()

Implements abstract java.util.logging.Handler.flush.

Doc from java.util.logging.Handler.flush.

Flush any buffered output.

Annotations

@Override

getJulRootLogger	back to summary
private static Logger getJulRootLogger()

getLog4jLogger	back to summary
private Logger getLog4jLogger(final LogRecord record) Return the log4j-Logger instance that will be used for logging. Handles null name case and appends configured suffix.

init	back to summary
protected void init(boolean debugOutput, String suffixToAppend, boolean propagateLevels) Perform init. of this handler with given configuration (typical use is for constructor). Annotations @SuppressFBWarnings:INFORMATION_EXPOSURE_THROUGH_AN_ERROR_MESSAGE justification:The data is available only in debug mode.

init

back to summary

protected void init(boolean debugOutput, String suffixToAppend, boolean propagateLevels)

Perform init. of this handler with given configuration (typical use is for constructor).

Annotations

@SuppressFBWarnings:INFORMATION_EXPOSURE_THROUGH_AN_ERROR_MESSAGE
justification:The data is available only in debug mode.

install back to summary

install	back to summary
public static void install(boolean removeHandlersForRootLogger, String suffixToAppend, boolean propagateLevels) Adds a new Log4jBridgeHandler instance to JUL's root logger. This is a programmatic alternative to specify `handlers = org.apache.logging.log4j.jul.Log4jBridgeHandler` and its configuration in logging.properties. Parameters removeHandlersForRootLogger:boolean true to remove all other installed handlers on JUL root level

public static void install(boolean removeHandlersForRootLogger, String suffixToAppend, boolean propagateLevels)

Adds a new Log4jBridgeHandler instance to JUL's root logger. This is a programmatic alternative to specify handlers = org.apache.logging.log4j.jul.Log4jBridgeHandler and its configuration in logging.properties.

Parameters

removeHandlersForRootLogger:boolean: true to remove all other installed handlers on JUL root level

propagateLogLevels	back to summary
private void propagateLogLevels(final org.apache.logging.log4j.core.config.Configuration config) Perform developer tests? (Should be unused/outcommented for real code)

propertyChange	back to summary
public void propertyChange(final PropertyChangeEvent evt) Implements java.beans.PropertyChangeListener.propertyChange. Doc from java.beans.PropertyChangeListener.propertyChange. This method gets called when a bound property is changed. Parameters evt:PropertyChangeEvent A PropertyChangeEvent object describing the event source and the property that has changed. Annotations @Override

propertyChange

back to summary

public void propertyChange(final PropertyChangeEvent evt)

Implements java.beans.PropertyChangeListener.propertyChange.

Doc from java.beans.PropertyChangeListener.propertyChange.

This method gets called when a bound property is changed.

Parameters

evt:PropertyChangeEvent: A PropertyChangeEvent object describing the event source and the property that has changed.

Annotations

@Override

publish back to summary

publish	back to summary
public void publish(final LogRecord record) Implements abstract java.util.logging.Handler.publish. Doc from java.util.logging.Handler.publish. Publish a `LogRecord`. The logging request was made initially to a `Logger` object, which initialized the `LogRecord` and forwarded it here. The `Handler` is responsible for formatting the message, when and if necessary. The formatting should include localization. Parameters record:LogRecord description of the log event. A null record is silently ignored and is not published Annotations @Override

public void publish(final LogRecord record)

Implements abstract java.util.logging.Handler.publish.

Doc from java.util.logging.Handler.publish.

Publish a LogRecord.

The logging request was made initially to a Logger object, which initialized the LogRecord and forwarded it here.

The Handler is responsible for formatting the message, when and if necessary. The formatting should include localization.

Parameters

record:LogRecord: description of the log event. A null record is silently ignored and is not published

Annotations

@Override

public Class Log4jBridgeHandler

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Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail