How to enable debug in slf4j Logger?

Question

How to globally enable debug for all the slf4j.Logger objects?

slf4j is an API. You need to configure the implementation ("binding") behind the API. — Thorbjørn Ravn Andersen, Jun 01 '12 at 09:58
@PeterRader, struggling to recollect that after 5 years. Soz, mate. — missingfaktor, Mar 09 '17 at 15:43
Sorry to ping such an old question, but I just want to cross-link https://stackoverflow.com/questions/14544991/how-to-configure-slf4j-simple which I found useful for configuring slf4j-simple to do the above. — Jon Sampson, Jan 23 '20 at 14:46

score 43 · Answer 1 · answered Jun 01 '12 at 11:39

43

Programmatically, with logback:

setLoggingLevel(ch.qos.logback.classic.Level.DEBUG);

where

public static void setLoggingLevel(ch.qos.logback.classic.Level level) {
    ch.qos.logback.classic.Logger root = (ch.qos.logback.classic.Logger) org.slf4j.LoggerFactory.getLogger(ch.qos.logback.classic.Logger.ROOT_LOGGER_NAME);
    root.setLevel(level);
}

answered Jun 01 '12 at 11:39

assylias

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Can I kiss you!?!!!? I have been searching how to disable this bloody logging in spring since 1 hour!!!!!!!!!!!!!!!! – EralpB Jan 30 '17 at 14:33
Does that only work if logback is your "backing" logging api? I thought slf4j was going to make a facility for this. – Constance Eustace Apr 04 '18 at 14:23
@roottraveller I don't think Tomcat uses logback by default. – assylias Aug 15 '19 at 06:59

score 17 · Answer 2 · answered Mar 30 '16 at 22:57

17

exists various capability to switch debug log on:
this article have good explanation all of those. to me good fit is:

Using slf4j with Log4j logger
create file src/main/resources/log4j.properties

log4j.rootLogger=DEBUG, STDOUT
log4j.logger.deng=INFO
log4j.appender.STDOUT=org.apache.log4j.ConsoleAppender
log4j.appender.STDOUT.layout=org.apache.log4j.PatternLayout
log4j.appender.STDOUT.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

answered Mar 30 '16 at 22:57

madjardi

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I'm pretty sure "log4j.logger.deng=INFO" isn't a valid option. – jsears May 25 '17 at 23:19
7

Actually, it is. It defines INFO as the level for all classes/Loggers under package `package deng;`. A more natural example line would be `log4j.logger.org.faceless.product.magic=INFO` with a reversed FQCN, which is more common. – mgaert May 30 '17 at 12:24

Onur Tokat · Answer 3 · 2020-08-24T12:49:28.500

11

Pass the System Property -Dorg.slf4j.simpleLogger.defaultLogLevel=DEBUG at your Java startup for the SLF4J Simple api

edited Aug 24 '20 at 12:49

answered Aug 24 '20 at 12:37

Onur Tokat

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So strange that this is not mentioned in the official SLF4J documents. – Cagin Uludamar Apr 13 '23 at 09:16

score 2 · Answer 4 · answered Jun 01 '12 at 10:00

2

Use logback as the slf4j binding.

The default behaviour without an configuration file is to log all events at level DEBUG and above to System.out. See http://logback.qos.ch/manual/configuration.html#automaticConf for details.

answered Jun 01 '12 at 10:00

Thorbjørn Ravn Andersen

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"Use logback as the slf4j binding." I am a noob. Can you please tell me how to do this? My google fu is failing me atm. – missingfaktor Jun 01 '12 at 10:53
Remove your current binding (see http://www.slf4j.org/faq.html#where_is_binding) and put logback-classic in your classpath. – Thorbjørn Ravn Andersen Jun 01 '12 at 11:00

Nick Dong · Answer 5 · 2022-12-04T17:54:44.400

If you are using slf4j with springboot, you just need to set debug level in application.properties.

logging.level.root=DEBUG

You also can set the specific part by setting logging.group.

Image that, if you have com.pxample, com.example, com.dxample in src/main/java/ and you setting:

logging.group.mycustomgroup=com.pxample, com.example
logging.level.mycustomgroup=DEBUG

, then only com.pxample, com.example will show debug output for you.

score 1 · Answer 6 · answered Dec 21 '20 at 22:44

1

Just add the following to the application.properties

logging.level.org.springframework.web=DEBUG
logging.level.org.springframework.context=DEBUG

answered Dec 21 '20 at 22:44

Manuel Mena

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score 0 · Answer 7 · answered Jun 01 '12 at 09:11

0

depends on what binding you are using... if e.g. it's log4j have a look at http://logging.apache.org/log4j/1.2/manual.html and its Configuration chapter

answered Jun 01 '12 at 09:11

Korgen

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I'm using: slf4j-api with slf4j-simple – White_King Feb 25 '19 at 05:44

score 0 · Answer 8 · answered Jun 01 '12 at 09:15

If you use log4j as the binding of slf4j you can crete a log4j.xml (or log4j.properties) file and add it to the classpath. An example could be:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false">
  <appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out" />
    <param name="Threshold" value="DEBUG" />
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d{HH:mm:ss,SSS} %-5p [%c{1}] %m%n" />
    </layout>
  </appender>
  <root>
    <appender-ref ref="CONSOLE" />
  </root>
</log4j:configuration>

score 0 · Answer 9 · edited Jun 01 '12 at 09:57

For log4j

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="true">

<!-- ============================== -->
<!-- Append messages to the console -->
<!-- ============================== -->

<appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out"/>
    <param name="Threshold" value="INFO"/>

    <layout class="org.apache.log4j.PatternLayout">
        <!-- The default pattern: Date Priority [Category] Message\n -->
        <param name="ConversionPattern" value="%d [%t] %-5p %c - %m%n"/>
    </layout>
</appender>

<appender name="web" class="org.apache.log4j.DailyRollingFileAppender">
    <param name="Threshold" value="DEBUG"/>
    <param name="Append" value="true"/>
    <param name="File" value="${catalina.home}/logs/web.log"/>
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d [%t] %-5p %c - %m%n"/>
    </layout>
</appender>

<category name="com.idc.scd" additivity="false">
    <priority value="${log4j.category.com.mypackage}"/>
    <appender-ref ref="web"/>
</category>

</log4j:configuration>

by this cofiguration your all "com.mypackage" logs will be written in "web.log" file under catalina.home.

Can you please suggest an alternative logging library where I won't have to add XML configuration files, and where debug/info/error are all enabled by default? — missingfaktor, Jun 01 '12 at 09:27
along with xml Log4j also provides java classes where you can add your log4jconfigurations. — Pramod Kumar, Jun 01 '12 at 09:33
I mean, is there a library that requires me to provide no configuration and has sane/expected defaults? — missingfaktor, Jun 01 '12 at 09:34
You can use java logging API which provides following log levels -SEVERE, WARNING, INFO, CONFIG, FINE, FINER, FINEST. — Pramod Kumar, Jun 01 '12 at 09:37

lainatnavi · Answer 10 · 2020-12-17T17:24:25.490

Here's a sample configuration I usually use to setup logging with logback.
Gradle dependencies (the same apply to Maven)

compile group: 'org.slf4j', name: 'slf4j-api', version: '1.7.25'
compile group: 'ch.qos.logback', name: 'logback-classic', version: '1.2.3'

logback.xml configuration to be placed in the project's classpath (src/main/resources)

<configuration>

    <statusListener class="ch.qos.logback.core.status.NopStatusListener" />

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <Pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36}.%M\(%line\) - %msg%n</Pattern>
        </layout>
    </appender>
    
    <!-- enable debug only on org.hibernate.SQL package -->
    <logger name="org.hibernate.SQL" level="debug" additivity="false">
        <appender-ref ref="STDOUT" />
    </logger>

    <root level="info">
        <appender-ref ref="STDOUT" />
    </root>

</configuration>

How to enable debug in slf4j Logger?

10 Answers10

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