slf4j简介和技术选型
市面上的日志框架:
JUL、JCL、Jboss-logging、logback、log4j、log4j2、slf4j....
日志门面 (日志的抽象层) | 日志实现 |
| Log4j JUL(java.util.logging) Log4j2 Logback |
左边选一个门面(抽象层)、右边来选一个实现;
日志门面: SLF4J;
日志实现:Logback;
SpringBoot:底层是Spring框架,Spring框架默认是用JCL;‘
SpringBoot选用 SLF4j和logback;
一、slf4j简介
slf4j(Simple logging facade for Java)是对所有日志框架制定的一种规范、标准、接口,并不是一个框架的具体的实现,因为接口并不能独立使用,需要和具体的日志框架实现配合使用
slf4j是门面模式的典型应用,外部与一个子系统的通信必须通过一个统一的外观对象进行,使得子系统更易于使用。
日志实现(log4j、logback、log4j2)
- log4j是apache实现的一个开源日志组件
- logback同样是由log4j的作者设计完成的,拥有更好的特性,用来取代log4j的一个日志框架,是slf4j的原生实现
- log4j2是log4j 1.x和logback的改进版,据说采用了一些新技术(无锁异步、等等),使得日志的吞吐量、性能比log4j 1.x提高10倍,并解决了一些死锁的bug,而且配置更加简单灵活。
为什么要使用slf4j
- SLF4J提供了统一的记录日志的接口,对不同日志系统的具体实现进行了抽象化,只要按照其提供的方法记录即可,最终日志的格式、记录级别、输出方式等通过绑定具体的日志系统来实现。在项目中使用了SLF4J记录日志,并且绑定了log4j,则日志会以log4j的风格输出;后期需要改为以logback的风格输出日志,只需要将jar包log4j替换成logback即可,不用修改项目中的代码。
- SLF4J支持
{}
作为占位符,等价于C语言中的%s
,而不必再进行字符串的拼接,效率有显著的提升
maven jar包
springBoot版本:
<!--boot版本:-->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.13.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<!--使用的log版本是(boot这一个就可以了):以下内容会自动导入-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
<version>2.2.13.RELEASE</version>
</dependency>
<!--logback-classic和logback-core版本是:-->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.2.3</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jul-to-slf4j</artifactId>
<version>1.7.30</version>
<scope>compile</scope>
</dependency>
二、实现原理
slf4j只是一个日志标准,并不是日志系统的具体实现。slf4j只提做两件事情:Logger类用来打日志,LoggerFactory类用来获取Logger;
- 提供日志接口 (Logger.class)
- 提供获取具体日志对象的方法 (LoggerFactory.class)
Logger.class
/**
* 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;
/**
* The org.slf4j.Logger interface is the main user entry point of SLF4J API.
* It is expected that logging takes place through concrete implementations
* of this interface.
* <p/>
* <h3>Typical usage pattern:</h3>
* <pre>
* import org.slf4j.Logger;
* import org.slf4j.LoggerFactory;
*
* public class Wombat {
*
* <span style="color:green">final static Logger logger = LoggerFactory.getLogger(Wombat.class);</span>
* Integer t;
* Integer oldT;
*
* public void setTemperature(Integer temperature) {
* oldT = t;
* t = temperature;
* <span style="color:green">logger.debug("Temperature set to {}. Old temperature was {}.", t, oldT);</span>
* if(temperature.intValue() > 50) {
* <span style="color:green">logger.info("Temperature has risen above 50 degrees.");</span>
* }
* }
* }
* </pre>
*
* Be sure to read the FAQ entry relating to <a href="../../../faq.html#logging_performance">parameterized
* logging</a>. Note that logging statements can be parameterized in
* <a href="../../../faq.html#paramException">presence of an exception/throwable</a>.
*
* <p>Once you are comfortable using loggers, i.e. instances of this interface, consider using
* <a href="MDC.html">MDC</a> as well as <a href="Marker.html">Markers</a>.</p>
*
* @author Ceki Gülcü
*/
public interface Logger {
/**
* Case insensitive String constant used to retrieve the name of the root logger.
*
* @since 1.3
*/
final public String ROOT_LOGGER_NAME = "ROOT";
/**
* Return the name of this <code>Logger</code> instance.
* @return name of this logger instance
*/
public String getName();
/**
* Is the logger instance enabled for the TRACE level?
*
* @return True if this Logger is enabled for the TRACE level,
* false otherwise.
* @since 1.4
*/
public boolean isTraceEnabled();
/**
* Log a message at the TRACE level.
*
* @param msg the message string to be logged
* @since 1.4
*/
public void trace(String msg);
/**
* Log a message at the TRACE level according to the specified format
* and argument.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the TRACE level. </p>
*
* @param format the format string
* @param arg the argument
* @since 1.4
*/
public void trace(String format, Object arg);
/**
* Log a message at the TRACE level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the TRACE level. </p>
*
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
* @since 1.4
*/
public void trace(String format, Object arg1, Object arg2);
/**
* Log a message at the TRACE level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the TRACE level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for TRACE. The variants taking {@link #trace(String, Object) one} and
* {@link #trace(String, Object, Object) two} arguments exist solely in order to avoid this hidden cost.</p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
* @since 1.4
*/
public void trace(String format, Object... arguments);
/**
* Log an exception (throwable) at the TRACE level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
* @since 1.4
*/
public void trace(String msg, Throwable t);
/**
* Similar to {@link #isTraceEnabled()} method except that the
* marker data is also taken into account.
*
* @param marker The marker data to take into consideration
* @return True if this Logger is enabled for the TRACE level,
* false otherwise.
*
* @since 1.4
*/
public boolean isTraceEnabled(Marker marker);
/**
* Log a message with the specific Marker at the TRACE level.
*
* @param marker the marker data specific to this log statement
* @param msg the message string to be logged
* @since 1.4
*/
public void trace(Marker marker, String msg);
/**
* This method is similar to {@link #trace(String, Object)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg the argument
* @since 1.4
*/
public void trace(Marker marker, String format, Object arg);
/**
* This method is similar to {@link #trace(String, Object, Object)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
* @since 1.4
*/
public void trace(Marker marker, String format, Object arg1, Object arg2);
/**
* This method is similar to {@link #trace(String, Object...)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param argArray an array of arguments
* @since 1.4
*/
public void trace(Marker marker, String format, Object... argArray);
/**
* This method is similar to {@link #trace(String, Throwable)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
* @since 1.4
*/
public void trace(Marker marker, String msg, Throwable t);
/**
* Is the logger instance enabled for the DEBUG level?
*
* @return True if this Logger is enabled for the DEBUG level,
* false otherwise.
*/
public boolean isDebugEnabled();
/**
* Log a message at the DEBUG level.
*
* @param msg the message string to be logged
*/
public void debug(String msg);
/**
* Log a message at the DEBUG level according to the specified format
* and argument.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the DEBUG level. </p>
*
* @param format the format string
* @param arg the argument
*/
public void debug(String format, Object arg);
/**
* Log a message at the DEBUG level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the DEBUG level. </p>
*
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void debug(String format, Object arg1, Object arg2);
/**
* Log a message at the DEBUG level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the DEBUG level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for DEBUG. The variants taking
* {@link #debug(String, Object) one} and {@link #debug(String, Object, Object) two}
* arguments exist solely in order to avoid this hidden cost.</p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void debug(String format, Object... arguments);
/**
* Log an exception (throwable) at the DEBUG level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void debug(String msg, Throwable t);
/**
* Similar to {@link #isDebugEnabled()} method except that the
* marker data is also taken into account.
*
* @param marker The marker data to take into consideration
* @return True if this Logger is enabled for the DEBUG level,
* false otherwise.
*/
public boolean isDebugEnabled(Marker marker);
/**
* Log a message with the specific Marker at the DEBUG level.
*
* @param marker the marker data specific to this log statement
* @param msg the message string to be logged
*/
public void debug(Marker marker, String msg);
/**
* This method is similar to {@link #debug(String, Object)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg the argument
*/
public void debug(Marker marker, String format, Object arg);
/**
* This method is similar to {@link #debug(String, Object, Object)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void debug(Marker marker, String format, Object arg1, Object arg2);
/**
* This method is similar to {@link #debug(String, Object...)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void debug(Marker marker, String format, Object... arguments);
/**
* This method is similar to {@link #debug(String, Throwable)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void debug(Marker marker, String msg, Throwable t);
/**
* Is the logger instance enabled for the INFO level?
*
* @return True if this Logger is enabled for the INFO level,
* false otherwise.
*/
public boolean isInfoEnabled();
/**
* Log a message at the INFO level.
*
* @param msg the message string to be logged
*/
public void info(String msg);
/**
* Log a message at the INFO level according to the specified format
* and argument.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the INFO level. </p>
*
* @param format the format string
* @param arg the argument
*/
public void info(String format, Object arg);
/**
* Log a message at the INFO level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the INFO level. </p>
*
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void info(String format, Object arg1, Object arg2);
/**
* Log a message at the INFO level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the INFO level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for INFO. The variants taking
* {@link #info(String, Object) one} and {@link #info(String, Object, Object) two}
* arguments exist solely in order to avoid this hidden cost.</p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void info(String format, Object... arguments);
/**
* Log an exception (throwable) at the INFO level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void info(String msg, Throwable t);
/**
* Similar to {@link #isInfoEnabled()} method except that the marker
* data is also taken into consideration.
*
* @param marker The marker data to take into consideration
* @return true if this logger is warn enabled, false otherwise
*/
public boolean isInfoEnabled(Marker marker);
/**
* Log a message with the specific Marker at the INFO level.
*
* @param marker The marker specific to this log statement
* @param msg the message string to be logged
*/
public void info(Marker marker, String msg);
/**
* This method is similar to {@link #info(String, Object)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg the argument
*/
public void info(Marker marker, String format, Object arg);
/**
* This method is similar to {@link #info(String, Object, Object)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void info(Marker marker, String format, Object arg1, Object arg2);
/**
* This method is similar to {@link #info(String, Object...)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void info(Marker marker, String format, Object... arguments);
/**
* This method is similar to {@link #info(String, Throwable)} method
* except that the marker data is also taken into consideration.
*
* @param marker the marker data for this log statement
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void info(Marker marker, String msg, Throwable t);
/**
* Is the logger instance enabled for the WARN level?
*
* @return True if this Logger is enabled for the WARN level,
* false otherwise.
*/
public boolean isWarnEnabled();
/**
* Log a message at the WARN level.
*
* @param msg the message string to be logged
*/
public void warn(String msg);
/**
* Log a message at the WARN level according to the specified format
* and argument.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the WARN level. </p>
*
* @param format the format string
* @param arg the argument
*/
public void warn(String format, Object arg);
/**
* Log a message at the WARN level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the WARN level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for WARN. The variants taking
* {@link #warn(String, Object) one} and {@link #warn(String, Object, Object) two}
* arguments exist solely in order to avoid this hidden cost.</p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void warn(String format, Object... arguments);
/**
* Log a message at the WARN level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the WARN level. </p>
*
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void warn(String format, Object arg1, Object arg2);
/**
* Log an exception (throwable) at the WARN level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void warn(String msg, Throwable t);
/**
* Similar to {@link #isWarnEnabled()} method except that the marker
* data is also taken into consideration.
*
* @param marker The marker data to take into consideration
* @return True if this Logger is enabled for the WARN level,
* false otherwise.
*/
public boolean isWarnEnabled(Marker marker);
/**
* Log a message with the specific Marker at the WARN level.
*
* @param marker The marker specific to this log statement
* @param msg the message string to be logged
*/
public void warn(Marker marker, String msg);
/**
* This method is similar to {@link #warn(String, Object)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg the argument
*/
public void warn(Marker marker, String format, Object arg);
/**
* This method is similar to {@link #warn(String, Object, Object)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void warn(Marker marker, String format, Object arg1, Object arg2);
/**
* This method is similar to {@link #warn(String, Object...)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void warn(Marker marker, String format, Object... arguments);
/**
* This method is similar to {@link #warn(String, Throwable)} method
* except that the marker data is also taken into consideration.
*
* @param marker the marker data for this log statement
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void warn(Marker marker, String msg, Throwable t);
/**
* Is the logger instance enabled for the ERROR level?
*
* @return True if this Logger is enabled for the ERROR level,
* false otherwise.
*/
public boolean isErrorEnabled();
/**
* Log a message at the ERROR level.
*
* @param msg the message string to be logged
*/
public void error(String msg);
/**
* Log a message at the ERROR level according to the specified format
* and argument.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the ERROR level. </p>
*
* @param format the format string
* @param arg the argument
*/
public void error(String format, Object arg);
/**
* Log a message at the ERROR level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous object creation when the logger
* is disabled for the ERROR level. </p>
*
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void error(String format, Object arg1, Object arg2);
/**
* Log a message at the ERROR level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the ERROR level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for ERROR. The variants taking
* {@link #error(String, Object) one} and {@link #error(String, Object, Object) two}
* arguments exist solely in order to avoid this hidden cost.</p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void error(String format, Object... arguments);
/**
* Log an exception (throwable) at the ERROR level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void error(String msg, Throwable t);
/**
* Similar to {@link #isErrorEnabled()} method except that the
* marker data is also taken into consideration.
*
* @param marker The marker data to take into consideration
* @return True if this Logger is enabled for the ERROR level,
* false otherwise.
*/
public boolean isErrorEnabled(Marker marker);
/**
* Log a message with the specific Marker at the ERROR level.
*
* @param marker The marker specific to this log statement
* @param msg the message string to be logged
*/
public void error(Marker marker, String msg);
/**
* This method is similar to {@link #error(String, Object)} method except that the
* marker data is also taken into consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg the argument
*/
public void error(Marker marker, String format, Object arg);
/**
* This method is similar to {@link #error(String, Object, Object)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arg1 the first argument
* @param arg2 the second argument
*/
public void error(Marker marker, String format, Object arg1, Object arg2);
/**
* This method is similar to {@link #error(String, Object...)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
public void error(Marker marker, String format, Object... arguments);
/**
* This method is similar to {@link #error(String, Throwable)}
* method except that the marker data is also taken into
* consideration.
*
* @param marker the marker data specific to this log statement
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
public void error(Marker marker, String msg, Throwable t);
}
View Code
LoggerFactory.classs
/**
* 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;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.LinkedBlockingQueue;
import org.slf4j.event.SubstituteLoggingEvent;
import org.slf4j.helpers.NOPLoggerFactory;
import org.slf4j.helpers.SubstituteLogger;
import org.slf4j.helpers.SubstituteLoggerFactory;
import org.slf4j.helpers.Util;
import org.slf4j.impl.StaticLoggerBinder;
/**
* The <code>LoggerFactory</code> is a utility class producing Loggers for
* various logging APIs, most notably for log4j, logback and JDK 1.4 logging.
* Other implementations such as {@link org.slf4j.impl.NOPLogger NOPLogger} and
* {@link org.slf4j.impl.SimpleLogger SimpleLogger} are also supported.
* <p/>
* <p/>
* <code>LoggerFactory</code> is essentially a wrapper around an
* {@link ILoggerFactory} instance bound with <code>LoggerFactory</code> at
* compile time.
* <p/>
* <p/>
* Please note that all methods in <code>LoggerFactory</code> are static.
*
*
* @author Alexander Dorokhine
* @author Robert Elliot
* @author Ceki Gülcü
*
*/
public final class LoggerFactory {
static final String CODES_PREFIX = "http://www.slf4j.org/codes.html";
static final String NO_STATICLOGGERBINDER_URL = CODES_PREFIX + "#StaticLoggerBinder";
static final String MULTIPLE_BINDINGS_URL = CODES_PREFIX + "#multiple_bindings";
static final String NULL_LF_URL = CODES_PREFIX + "#null_LF";
static final String VERSION_MISMATCH = CODES_PREFIX + "#version_mismatch";
static final String SUBSTITUTE_LOGGER_URL = CODES_PREFIX + "#substituteLogger";
static final String LOGGER_NAME_MISMATCH_URL = CODES_PREFIX + "#loggerNameMismatch";
static final String REPLAY_URL = CODES_PREFIX + "#replay";
static final String UNSUCCESSFUL_INIT_URL = CODES_PREFIX + "#unsuccessfulInit";
static final String UNSUCCESSFUL_INIT_MSG = "org.slf4j.LoggerFactory in failed state. Original exception was thrown EARLIER. See also " + UNSUCCESSFUL_INIT_URL;
static final int UNINITIALIZED = 0;
static final int ONGOING_INITIALIZATION = 1;
static final int FAILED_INITIALIZATION = 2;
static final int SUCCESSFUL_INITIALIZATION = 3;
static final int NOP_FALLBACK_INITIALIZATION = 4;
static volatile int INITIALIZATION_STATE = UNINITIALIZED;
static final SubstituteLoggerFactory SUBST_FACTORY = new SubstituteLoggerFactory();
static final NOPLoggerFactory NOP_FALLBACK_FACTORY = new NOPLoggerFactory();
// Support for detecting mismatched logger names.
static final String DETECT_LOGGER_NAME_MISMATCH_PROPERTY = "slf4j.detectLoggerNameMismatch";
static final String JAVA_VENDOR_PROPERTY = "java.vendor.url";
static boolean DETECT_LOGGER_NAME_MISMATCH = Util.safeGetBooleanSystemProperty(DETECT_LOGGER_NAME_MISMATCH_PROPERTY);
/**
* It is LoggerFactory's responsibility to track version changes and manage
* the compatibility list.
* <p/>
* <p/>
* It is assumed that all versions in the 1.6 are mutually compatible.
*/
static private final String[] API_COMPATIBILITY_LIST = new String[] { "1.6", "1.7" };
// private constructor prevents instantiation
private LoggerFactory() {
}
/**
* Force LoggerFactory to consider itself uninitialized.
* <p/>
* <p/>
* This method is intended to be called by classes (in the same package) for
* testing purposes. This method is internal. It can be modified, renamed or
* removed at any time without notice.
* <p/>
* <p/>
* You are strongly discouraged from calling this method in production code.
*/
static void reset() {
INITIALIZATION_STATE = UNINITIALIZED;
}
private final static void performInitialization() {
bind();
if (INITIALIZATION_STATE == SUCCESSFUL_INITIALIZATION) {
versionSanityCheck();
}
}
private static boolean messageContainsOrgSlf4jImplStaticLoggerBinder(String msg) {
if (msg == null)
return false;
if (msg.contains("org/slf4j/impl/StaticLoggerBinder"))
return true;
if (msg.contains("org.slf4j.impl.StaticLoggerBinder"))
return true;
return false;
}
private final static void bind() {
try {
Set<URL> staticLoggerBinderPathSet = null;
// skip check under android, see also
// http://jira.qos.ch/browse/SLF4J-328
if (!isAndroid()) {
staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();
reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
}
// the next line does the binding
StaticLoggerBinder.getSingleton();
INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;
reportActualBinding(staticLoggerBinderPathSet);
} catch (NoClassDefFoundError ncde) {
String msg = ncde.getMessage();
if (messageContainsOrgSlf4jImplStaticLoggerBinder(msg)) {
INITIALIZATION_STATE = NOP_FALLBACK_INITIALIZATION;
Util.report("Failed to load class \"org.slf4j.impl.StaticLoggerBinder\".");
Util.report("Defaulting to no-operation (NOP) logger implementation");
Util.report("See " + NO_STATICLOGGERBINDER_URL + " for further details.");
} else {
failedBinding(ncde);
throw ncde;
}
} catch (java.lang.NoSuchMethodError nsme) {
String msg = nsme.getMessage();
if (msg != null && msg.contains("org.slf4j.impl.StaticLoggerBinder.getSingleton()")) {
INITIALIZATION_STATE = FAILED_INITIALIZATION;
Util.report("slf4j-api 1.6.x (or later) is incompatible with this binding.");
Util.report("Your binding is version 1.5.5 or earlier.");
Util.report("Upgrade your binding to version 1.6.x.");
}
throw nsme;
} catch (Exception e) {
failedBinding(e);
throw new IllegalStateException("Unexpected initialization failure", e);
} finally {
postBindCleanUp();
}
}
private static void postBindCleanUp() {
fixSubstituteLoggers();
replayEvents();
// release all resources in SUBST_FACTORY
SUBST_FACTORY.clear();
}
private static void fixSubstituteLoggers() {
synchronized (SUBST_FACTORY) {
SUBST_FACTORY.postInitialization();
for (SubstituteLogger substLogger : SUBST_FACTORY.getLoggers()) {
Logger logger = getLogger(substLogger.getName());
substLogger.setDelegate(logger);
}
}
}
static void failedBinding(Throwable t) {
INITIALIZATION_STATE = FAILED_INITIALIZATION;
Util.report("Failed to instantiate SLF4J LoggerFactory", t);
}
private static void replayEvents() {
final LinkedBlockingQueue<SubstituteLoggingEvent> queue = SUBST_FACTORY.getEventQueue();
final int queueSize = queue.size();
int count = 0;
final int maxDrain = 128;
List<SubstituteLoggingEvent> eventList = new ArrayList<SubstituteLoggingEvent>(maxDrain);
while (true) {
int numDrained = queue.drainTo(eventList, maxDrain);
if (numDrained == 0)
break;
for (SubstituteLoggingEvent event : eventList) {
replaySingleEvent(event);
if (count++ == 0)
emitReplayOrSubstituionWarning(event, queueSize);
}
eventList.clear();
}
}
private static void emitReplayOrSubstituionWarning(SubstituteLoggingEvent event, int queueSize) {
if (event.getLogger().isDelegateEventAware()) {
emitReplayWarning(queueSize);
} else if (event.getLogger().isDelegateNOP()) {
// nothing to do
} else {
emitSubstitutionWarning();
}
}
private static void replaySingleEvent(SubstituteLoggingEvent event) {
if (event == null)
return;
SubstituteLogger substLogger = event.getLogger();
String loggerName = substLogger.getName();
if (substLogger.isDelegateNull()) {
throw new IllegalStateException("Delegate logger cannot be null at this state.");
}
if (substLogger.isDelegateNOP()) {
// nothing to do
} else if (substLogger.isDelegateEventAware()) {
substLogger.log(event);
} else {
Util.report(loggerName);
}
}
private static void emitSubstitutionWarning() {
Util.report("The following set of substitute loggers may have been accessed");
Util.report("during the initialization phase. Logging calls during this");
Util.report("phase were not honored. However, subsequent logging calls to these");
Util.report("loggers will work as normally expected.");
Util.report("See also " + SUBSTITUTE_LOGGER_URL);
}
private static void emitReplayWarning(int eventCount) {
Util.report("A number (" + eventCount + ") of logging calls during the initialization phase have been intercepted and are");
Util.report("now being replayed. These are subject to the filtering rules of the underlying logging system.");
Util.report("See also " + REPLAY_URL);
}
private final static void versionSanityCheck() {
try {
String requested = StaticLoggerBinder.REQUESTED_API_VERSION;
boolean match = false;
for (String aAPI_COMPATIBILITY_LIST : API_COMPATIBILITY_LIST) {
if (requested.startsWith(aAPI_COMPATIBILITY_LIST)) {
match = true;
}
}
if (!match) {
Util.report("The requested version " + requested + " by your slf4j binding is not compatible with "
+ Arrays.asList(API_COMPATIBILITY_LIST).toString());
Util.report("See " + VERSION_MISMATCH + " for further details.");
}
} catch (java.lang.NoSuchFieldError nsfe) {
// given our large user base and SLF4J's commitment to backward
// compatibility, we cannot cry here. Only for implementations
// which willingly declare a REQUESTED_API_VERSION field do we
// emit compatibility warnings.
} catch (Throwable e) {
// we should never reach here
Util.report("Unexpected problem occured during version sanity check", e);
}
}
// We need to use the name of the StaticLoggerBinder class, but we can't
// reference
// the class itself.
private static String STATIC_LOGGER_BINDER_PATH = "org/slf4j/impl/StaticLoggerBinder.class";
static Set<URL> findPossibleStaticLoggerBinderPathSet() {
// use Set instead of list in order to deal with bug #138
// LinkedHashSet appropriate here because it preserves insertion order
// during iteration
Set<URL> staticLoggerBinderPathSet = new LinkedHashSet<URL>();
try {
ClassLoader loggerFactoryClassLoader = LoggerFactory.class.getClassLoader();
Enumeration<URL> paths;
if (loggerFactoryClassLoader == null) {
paths = ClassLoader.getSystemResources(STATIC_LOGGER_BINDER_PATH);
} else {
paths = loggerFactoryClassLoader.getResources(STATIC_LOGGER_BINDER_PATH);
}
while (paths.hasMoreElements()) {
URL path = paths.nextElement();
staticLoggerBinderPathSet.add(path);
}
} catch (IOException ioe) {
Util.report("Error getting resources from path", ioe);
}
return staticLoggerBinderPathSet;
}
private static boolean isAmbiguousStaticLoggerBinderPathSet(Set<URL> binderPathSet) {
return binderPathSet.size() > 1;
}
/**
* Prints a warning message on the console if multiple bindings were found
* on the class path. No reporting is done otherwise.
*
*/
private static void reportMultipleBindingAmbiguity(Set<URL> binderPathSet) {
if (isAmbiguousStaticLoggerBinderPathSet(binderPathSet)) {
Util.report("Class path contains multiple SLF4J bindings.");
for (URL path : binderPathSet) {
Util.report("Found binding in [" + path + "]");
}
Util.report("See " + MULTIPLE_BINDINGS_URL + " for an explanation.");
}
}
private static boolean isAndroid() {
String vendor = Util.safeGetSystemProperty(JAVA_VENDOR_PROPERTY);
if (vendor == null)
return false;
return vendor.toLowerCase().contains("android");
}
private static void reportActualBinding(Set<URL> binderPathSet) {
// binderPathSet can be null under Android
if (binderPathSet != null && isAmbiguousStaticLoggerBinderPathSet(binderPathSet)) {
Util.report("Actual binding is of type [" + StaticLoggerBinder.getSingleton().getLoggerFactoryClassStr() + "]");
}
}
/**
* Return a logger named according to the name parameter using the
* statically bound {@link ILoggerFactory} instance.
*
* @param name
* The name of the logger.
* @return logger
*/
public static Logger getLogger(String name) {
ILoggerFactory iLoggerFactory = getILoggerFactory();
return iLoggerFactory.getLogger(name);
}
/**
* Return a logger named corresponding to the class passed as parameter,
* using the statically bound {@link ILoggerFactory} instance.
*
* <p>
* In case the the <code>clazz</code> parameter differs from the name of the
* caller as computed internally by SLF4J, a logger name mismatch warning
* will be printed but only if the
* <code>slf4j.detectLoggerNameMismatch</code> system property is set to
* true. By default, this property is not set and no warnings will be
* printed even in case of a logger name mismatch.
*
* @param clazz
* the returned logger will be named after clazz
* @return logger
*
*
* @see <a
* href="http://www.slf4j.org/codes.html#loggerNameMismatch">Detected
* logger name mismatch</a>
*/
public static Logger getLogger(Class<?> clazz) {
Logger logger = getLogger(clazz.getName());
if (DETECT_LOGGER_NAME_MISMATCH) {
Class<?> autoComputedCallingClass = Util.getCallingClass();
if (autoComputedCallingClass != null && nonMatchingClasses(clazz, autoComputedCallingClass)) {
Util.report(String.format("Detected logger name mismatch. Given name: \"%s\"; computed name: \"%s\".", logger.getName(),
autoComputedCallingClass.getName()));
Util.report("See " + LOGGER_NAME_MISMATCH_URL + " for an explanation");
}
}
return logger;
}
private static boolean nonMatchingClasses(Class<?> clazz, Class<?> autoComputedCallingClass) {
return !autoComputedCallingClass.isAssignableFrom(clazz);
}
/**
* Return the {@link ILoggerFactory} instance in use.
* <p/>
* <p/>
* ILoggerFactory instance is bound with this class at compile time.
*
* @return the ILoggerFactory instance in use
*/
public static ILoggerFactory getILoggerFactory() {
if (INITIALIZATION_STATE == UNINITIALIZED) {
synchronized (LoggerFactory.class) {
if (INITIALIZATION_STATE == UNINITIALIZED) {
INITIALIZATION_STATE = ONGOING_INITIALIZATION;
performInitialization();
}
}
}
switch (INITIALIZATION_STATE) {
case SUCCESSFUL_INITIALIZATION:
return StaticLoggerBinder.getSingleton().getLoggerFactory();
case NOP_FALLBACK_INITIALIZATION:
return NOP_FALLBACK_FACTORY;
case FAILED_INITIALIZATION:
throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG);
case ONGOING_INITIALIZATION:
// support re-entrant behavior.
// See also http://jira.qos.ch/browse/SLF4J-97
return SUBST_FACTORY;
}
throw new IllegalStateException("Unreachable code");
}
}
View Code
这里看下获取getLogger函数的源码,我们发现LoggerFactory.getLogger()首先获取一个ILoggerFactory接口,然后使用该接口获取具体的Logger。
获取ILoggerFactory的时候用到了一个 LoggerContext 类,仔细研究我们会发现LoggerContext 这个类并不是slf4j-api这个包中的类,而是实现日志框架里的类,所有的实现框架都需要定义该类,提供具体的Logger实现。
三、SLF4j使用
1、如何在系统中使用SLF4j https://www.slf4j.org
以后开发的时候,日志记录方法的调用,不应该来直接调用日志的实现类,而是调用日志抽象层里面的方法;
给系统里面导入slf4j的jar和 logback的实现jar
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class HelloWorld {
public static void main(String[] args) {
Logger logger = LoggerFactory.getLogger(HelloWorld.class);
logger.info("Hello World");
}
}
每一个日志的实现框架都有自己的配置文件。使用slf4j以后,配置文件还是做成日志实现框架自己本身的配置文件;
a(slf4j+logback): Spring(commons-logging)、Hibernate(jboss-logging)、MyBatis、xxxx
统一日志记录,即使是别的框架和我一起统一使用slf4j进行输出?
如何让系统中所有的日志都统一到slf4j;
1、将系统中其他日志框架先排除出去;
2、用中间包来替换原有的日志框架;
3、我们导入slf4j其他的实现
二、SpringBoot日志关系
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.13.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
SpringBoot使用它来做日志功能:
<!--不需要导入-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
<version>2.2.13.RELEASE</version>
</dependency>
底层依赖关系
jcl-over-self4j
总结:
1)、SpringBoot底层也是使用slf4j+logback的方式进行日志记录
2)、SpringBoot也把其他的日志都替换成了slf4j;
3)、中间替换包?
@SuppressWarnings("rawtypes")
public abstract class LogFactory {
static String UNSUPPORTED_OPERATION_IN_JCL_OVER_SLF4J = "http://www.slf4j.org/codes.html#unsupported_operation_in_jcl_over_slf4j";
static LogFactory logFactory = new SLF4JLogFactory();
4)、如果我们普通的 maven 项目要引入其他框架?一定要把spring框架的默认日志依赖移除掉?
Spring框架用的是commons-logging;
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<exclusions>
<exclusion>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
SpringBoot能自动适配所有的日志,而且底层使用slf4j+logback的方式记录日志,引入其他框架的时候,只需要把这个框架依赖的日志框架排除掉即可
三、logback简介
logback是log4j创始人写的,性能比log4j要好,目前主要分为3个模块
- logback-core:核心代码模块
- logback-classic:log4j的一个改良版本,同时实现了
slf4j
的接口,这样你如果之后要切换其他日志组件也是一件很容易的事 - logback-access:访问模块与Servlet容器集成提供通过Http来访问日志的功能
三、日志使用
1、logback-spring.xml配置
<?xml version="1.0" encoding="UTF-8"?>
<!--
scan:当此属性设置为true时,配置文件如果发生改变,将会被重新加载,默认值为true。
scanPeriod:设置监测配置文件是否有修改的时间间隔,如果没有给出时间单位,默认单位是毫秒当scan为true时,此属性生效。默认的时间间隔为1分钟。
debug:当此属性设置为true时,将打印出logback内部日志信息,实时查看logback运行状态。默认值为false。
-->
<configuration scan="false" scanPeriod="60 seconds" debug="false">
<!-- 定义日志的根目录为项目的根目录,前面不要加"/",加了会默认会认为是根目录,提示 classnotfond -->
<property name="LOG_HOME" value="app/log"/>
<!-- 定义日志文件名称 -->
<property name="appName" value="logbackBootText"/>
<!-- ConsoleAppender 用于控制台输出 -->
<appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
<!--
日志输出格式:
%d表示日期时间,
%thread表示线程名,
%-5level:级别从左显示5个字符宽度
%logger{50} 表示logger名字最长50个字符,否则按照句点分割。
%msg:日志消息,
%n是换行符
-->
<layout class="ch.qos.logback.classic.PatternLayout">
<!--springProfile可以指定某段配置只在某个环境下生效-->
<!--如果使用logback.xml作为日志配置文件,还要使用profile功能,会有以下错误no applicable action for [springProfile]-->
<springProfile name="dev">
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} ----> [%thread] ---> %-5level %logger{50} - %msg%n</pattern>
</springProfile>
<springProfile name="!dev">
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} ==== [%thread] ==== %-5level %logger{50} - %msg%n</pattern>
</springProfile>
</layout>
</appender>
<!-- 滚动记录文件,先将日志记录到指定文件,当符合某个条件时,将日志记录到其他文件 -->
<appender name="appLogAppender" class="ch.qos.logback.core.rolling.RollingFileAppender">
<!--定义日志输出的路径和名称-->
<!-- 指定日志文件的名称 -->
<!--这里的scheduler.manager.server.home 没有在上面的配置中设定,所以会使用java启动时配置的值-->
<!--比如通过 java -Dscheduler.manager.server.home=/path/to XXXX 配置该属性-->
<!--<file>${scheduler.manager.server.home}/${LOG_HOME}/${appName}.log</file>-->
<!--当发生滚动时,决定 RollingFileAppender 的行为,涉及文件移动和重命名
TimeBasedRollingPolicy: 最常用的滚动策略,它根据时间来制定滚动策略,既负责滚动也负责出发滚动。“%d”可以包含一个java.text.SimpleDateFormat指定的时间格式,-->
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<!--滚动时产生的文件的存放位置及文件名称 %d{yyyy-MM-dd}:按天进行日志滚动
%i:当文件大小超过maxFileSize时,按照i进行文件滚动-->
<fileNamePattern>${LOG_HOME}/${appName}-%d{yyyy-MM-dd}-%i.log</fileNamePattern>
<!--可选节点,控制保留的归档文件的最大数量,超出数量就删除旧文件。假设设置每天滚动,
且maxHistory是365,则只保存最近365天的文件,删除之前的旧文件。注意,删除旧文件是,
那些为了归档而创建的目录也会被删除。-->
<MaxHistory>365</MaxHistory>
<!-- 该属性在 1.1.6版本后 才开始支持,日志量最大20GB-->
<totalSizeCap>20GB</totalSizeCap>
<!--当日志文件超过maxFileSize指定的大小是,根据上面提到的%i进行日志文件滚动 注意此处配置 SizeBasedTriggeringPolicy 是无法实现按文件大小进行滚动的,必须配置 timeBasedFileNamingAndTriggeringPolicy-->
<timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
<maxFileSize>100MB</maxFileSize>
</timeBasedFileNamingAndTriggeringPolicy>
</rollingPolicy>
<!-- 日志输出格式: -->
<layout class="ch.qos.logback.classic.PatternLayout">
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [ %thread ] ->> [ %-5level ] [ %logger{50} : %line ] ->> %msg%n
</pattern>
</layout>
</appender>
<!-- 滚动记录文件,先将日志记录到指定文件,当符合某个条件时,将日志记录到其他文件 -->
<appender name="appLogAppenderBoot" class="ch.qos.logback.core.rolling.RollingFileAppender">
<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
<fileNamePattern>${LOG_HOME}/boot-${appName}-%d{yyyy-MM-dd}-%i.log</fileNamePattern>
<MaxHistory>365</MaxHistory>
<timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
<maxFileSize>100MB</maxFileSize>
</timeBasedFileNamingAndTriggeringPolicy>
</rollingPolicy>
<layout class="ch.qos.logback.classic.PatternLayout">
<pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [ %thread ] -> [ %-5level ] [ %logger{50} : %line ] -> %msg%n</pattern>
</layout>
</appender>
<!--root是默认的logger,root与logger是父子关系,没有特别定义则默认为root,任何一个类只会和一个logger对应,
要么是定义的logger,要么是root,判断的关键在于找到这个logger,然后判断这个logger的appender和level。 -->
<root level="DEBUG">
<!--定义了三个appender,日志会通过往这这些appender里面写-->
<appender-ref ref="stdout"/>
<appender-ref ref="appLogAppender"/>
<appender-ref ref="appLogAppenderBoot"/>
</root>
<!--logger主要用于存放日志对象,也可以定义日志类型、级别-->
<!--name:表示匹配的logger类型前缀,也就是包的前半部分-->
<!--level:要记录的日志级别,包括 TRACE < DEBUG < INFO < WARN < ERROR 越往后越精简-->
<!--additivity:作用在于children-logger是否使用 rootLogger配置的appender进行输出,-->
<!--false:表示只用当前logger的appender-ref,true:表示当前logger的appender-ref和rootLogger的appender-ref都有效-->
<!-- Spring framework logger 记录 spring 的日志 -->
<logger name="org.springframework.boot" level="debug" additivity="false">
<appender-ref ref="appLogAppenderBoot"/>
</logger>
<!--通过 LoggerFactory.getLogger("mytest") 可以获取到这个logger-->
<!--由于这个logger自动继承了root的appender,root中已经有stdout的appender了,自己这边又引入了stdout的appender-->
<!--如果没有设置 additivity="false" ,就会导致一条日志在控制台输出两次的情况,原因是:没有写additivity会用 rootlogger 输出日志,而它下面有三个appender,单appLogAppenderBoot经过自定义,不会输出,stdout则会打印两遍-->
<!--additivity表示要不要使用rootLogger配置的appender进行输出-->
<logger name="com.tuniu" level="debug" additivity="false">
<!--即输出到appLogAppender,又输出到stdout-->
<appender-ref ref="appLogAppender"/>
<appender-ref ref="stdout"/>
</logger>
<!--对于类路径以 com.tuniu 开头的Logger,输出级别设置为 warn,-->
<!--这个logger没有指定appender,它会继承root节点中定义的那些appender-->
<!--注意,如果名称相同,两个 logger 会有属性互补机制;而且以最后一个加载的属性为准,可以理解为 boot的 bootstrap.properties与 application.yml-->
<!--
<logger name="com.tuniu" level="warn"/>
如果将上面的这段配置放开,就如同写了:
<logger name="com.tuniu" level="warn" additivity="false">
<appender-ref ref="appLogAppender"/>
</logger>
-->
<!--由于设置了 additivity="false" ,所以输出时不会使用rootLogger的appender-->
<!--但是这个logger本身又没有配置 appender,所以使用这个logger输出日志的话就不会输出到任何地方-->
<!-- <logger name="mytest2" level="info" additivity="false"/>-->
</configuration>
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