org.slf4j.bridge.SLF4JBridgeHandler Maven / Gradle / Ivy
/**
* Copyright (c) 2004-2011 QOS.ch
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
package org.slf4j.bridge;
import java.text.MessageFormat;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.LogRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.spi.LocationAwareLogger;
// Based on http://jira.qos.ch/browse/SLF4J-30
/**
* Bridge/route all JUL log records to the SLF4J API.
*
Essentially, the idea is to install on the root logger an instance of
* {@link SLF4JBridgeHandler} as the sole JUL handler in the system. Subsequently, the
* SLF4JBridgeHandler instance will redirect all JUL log records are redirected
* to the SLF4J API based on the following mapping of levels:
*
*
* FINEST -> TRACE
* FINER -> DEBUG
* FINE -> DEBUG
* INFO -> INFO
* WARNING -> WARN
* SEVERE -> ERROR
* Programmatic installation:
*
* // Optionally remove existing handlers attached to j.u.l root logger
* SLF4JBridgeHandler.removeHandlersForRootLogger(); // (since SLF4J 1.6.5)
* // add SLF4JBridgeHandler to j.u.l's root logger, should be done once during
* // the initialization phase of your application
* SLF4JBridgeHandler.install();
* Installation via logging.properties configuration file:
*
* // register SLF4JBridgeHandler as handler for the j.u.l. root logger
* handlers = org.slf4j.bridge.SLF4JBridgeHandler
* Once SLF4JBridgeHandler is installed, logging by j.u.l. loggers will be directed to
* SLF4J. Example:
*
* import java.util.logging.Logger;
* ...
* // usual pattern: get a Logger and then log a message
* Logger julLogger = Logger.getLogger("org.wombat");
* julLogger.fine("hello world"); // this will get redirected to SLF4J
*
* Please note that translating a java.util.logging event into SLF4J incurs the
* cost of constructing {@link LogRecord} instance regardless of whether the
* SLF4J logger is disabled for the given level. Consequently, j.u.l. to
* SLF4J translation can seriously increase the cost of disabled logging
* statements (60 fold or 6000% increase) and measurably impact the performance of enabled log
* statements (20% overall increase). Please note that as of logback-version 0.9.25,
* it is possible to completely eliminate the 60-fold translation overhead for disabled
* log statements with the help of LevelChangePropagator.
*
*
*
If you are concerned about application performance, then use of SLF4JBridgeHandler
* is appropriate only if any of the following conditions is true:
*
* - few j.u.l. logging statements are in play
* - LevelChangePropagator has been installed
*
*
* As a Java 9/Jigsaw module
*
* As of SLF4J 2.0x, the module name for jul-to-slf4j.jar is
* jul.to.slf4j. In SLF4J 1.7.x it was declared via an Automatic-Module-Name statement
* as jul_to_slf4j (note the two underscores).
*
* @author Christian Stein
* @author Joern Huxhorn
* @author Ceki Gülcü
* @author Darryl Smith
* @since 1.5.1
*/
public class SLF4JBridgeHandler extends Handler {
// The caller is java.util.logging.Logger
private static final String FQCN = java.util.logging.Logger.class.getName();
private static final String UNKNOWN_LOGGER_NAME = "unknown.jul.logger";
private static final int TRACE_LEVEL_THRESHOLD = Level.FINEST.intValue();
private static final int DEBUG_LEVEL_THRESHOLD = Level.FINE.intValue();
private static final int INFO_LEVEL_THRESHOLD = Level.INFO.intValue();
private static final int WARN_LEVEL_THRESHOLD = Level.WARNING.intValue();
/**
* Adds a SLF4JBridgeHandler instance to jul's root logger.
*
*
This handler will redirect j.u.l. logging to SLF4J. However, only logs enabled
* in j.u.l. will be redirected. For example, if a log statement invoking a
* j.u.l. logger is disabled, then the corresponding non-event will not
* reach SLF4JBridgeHandler and cannot be redirected.
*/
public static void install() {
LogManager.getLogManager().getLogger("").addHandler(new SLF4JBridgeHandler());
}
private static java.util.logging.Logger getRootLogger() {
return LogManager.getLogManager().getLogger("");
}
/**
* Removes previously installed SLF4JBridgeHandler instances. See also
* {@link #install()}.
*
* @throws SecurityException A SecurityException is thrown, if a security manager
* exists and if the caller does not have
* LoggingPermission("control").
*/
public static void uninstall() throws SecurityException {
java.util.logging.Logger rootLogger = getRootLogger();
Handler[] handlers = rootLogger.getHandlers();
for (Handler handler : handlers) {
if (handler instanceof SLF4JBridgeHandler) {
rootLogger.removeHandler(handler);
}
}
}
/**
* Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
*
* @return true if SLF4JBridgeHandler is already installed, false otherwise
*
*/
public static boolean isInstalled() {
java.util.logging.Logger rootLogger = getRootLogger();
Handler[] handlers = rootLogger.getHandlers();
for (Handler handler : handlers) {
if (handler instanceof SLF4JBridgeHandler) {
return true;
}
}
return false;
}
/**
* Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
* @since 1.6.5
*/
public static void removeHandlersForRootLogger() {
java.util.logging.Logger rootLogger = getRootLogger();
java.util.logging.Handler[] handlers = rootLogger.getHandlers();
for (Handler handler : handlers) {
rootLogger.removeHandler(handler);
}
}
/**
* Initialize this handler.
*/
public SLF4JBridgeHandler() {
}
/**
* No-op implementation.
*/
public void close() {
// empty
}
/**
* No-op implementation.
*/
public void flush() {
// empty
}
/**
* Return the Logger instance that will be used for logging.
*
* @param record a LogRecord
* @return an SLF4J logger corresponding to the record parameter's logger name
*/
protected Logger getSLF4JLogger(LogRecord record) {
String name = record.getLoggerName();
if (name == null) {
name = UNKNOWN_LOGGER_NAME;
}
return LoggerFactory.getLogger(name);
}
protected void callLocationAwareLogger(LocationAwareLogger lal, LogRecord record) {
int julLevelValue = record.getLevel().intValue();
int slf4jLevel;
if (julLevelValue <= TRACE_LEVEL_THRESHOLD) {
slf4jLevel = LocationAwareLogger.TRACE_INT;
} else if (julLevelValue <= DEBUG_LEVEL_THRESHOLD) {
slf4jLevel = LocationAwareLogger.DEBUG_INT;
} else if (julLevelValue <= INFO_LEVEL_THRESHOLD) {
slf4jLevel = LocationAwareLogger.INFO_INT;
} else if (julLevelValue <= WARN_LEVEL_THRESHOLD) {
slf4jLevel = LocationAwareLogger.WARN_INT;
} else {
slf4jLevel = LocationAwareLogger.ERROR_INT;
}
String i18nMessage = getMessageI18N(record);
lal.log(null, FQCN, slf4jLevel, i18nMessage, null, record.getThrown());
}
protected void callPlainSLF4JLogger(Logger slf4jLogger, LogRecord record) {
String i18nMessage = getMessageI18N(record);
int julLevelValue = record.getLevel().intValue();
if (julLevelValue <= TRACE_LEVEL_THRESHOLD) {
slf4jLogger.trace(i18nMessage, record.getThrown());
} else if (julLevelValue <= DEBUG_LEVEL_THRESHOLD) {
slf4jLogger.debug(i18nMessage, record.getThrown());
} else if (julLevelValue <= INFO_LEVEL_THRESHOLD) {
slf4jLogger.info(i18nMessage, record.getThrown());
} else if (julLevelValue <= WARN_LEVEL_THRESHOLD) {
slf4jLogger.warn(i18nMessage, record.getThrown());
} else {
slf4jLogger.error(i18nMessage, record.getThrown());
}
}
/**
* Get the record's message, possibly via a resource bundle.
*
* @param record
* @return
*/
private String getMessageI18N(LogRecord record) {
String message = record.getMessage();
if (message == null) {
return null;
}
ResourceBundle bundle = record.getResourceBundle();
if (bundle != null) {
try {
message = bundle.getString(message);
} catch (MissingResourceException e) {
}
}
Object[] params = record.getParameters();
// avoid formatting when there are no or 0 parameters. see also
// http://jira.qos.ch/browse/SLF4J-203
if (params != null && params.length > 0) {
try {
message = MessageFormat.format(message, params);
} catch (IllegalArgumentException e) {
// default to the same behavior as in java.util.logging.Formatter.formatMessage(LogRecord)
// see also http://jira.qos.ch/browse/SLF4J-337
return message;
}
}
return message;
}
/**
* Publish a LogRecord.
*
* The logging request was made initially to a Logger object, which
* initialized the LogRecord and forwarded it here.
*
* This handler ignores the Level attached to the LogRecord, as SLF4J cares
* about discarding log statements.
*
* @param record Description of the log event. A null record is silently ignored
* and is not published.
*/
public void publish(LogRecord record) {
// Silently ignore null records.
if (record == null) {
return;
}
Logger slf4jLogger = getSLF4JLogger(record);
// this is a check to avoid calling the underlying logging system
// with a null message. While it is legitimate to invoke j.u.l. with
// a null message, other logging frameworks do not support this.
// see also http://jira.qos.ch/browse/SLF4J-99
if (record.getMessage() == null) {
record.setMessage("");
}
if (slf4jLogger instanceof LocationAwareLogger) {
callLocationAwareLogger((LocationAwareLogger) slf4jLogger, record);
} else {
callPlainSLF4JLogger(slf4jLogger, record);
}
}
}