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Questions tagged [log4j]

log4j is a popular Java-based logging utility. It is a project of the Apache Software Foundation and is licensed under The Apache Software License, Version 2.0

Apache Log4j is a Java-based logging utility. It is a project of the Apache Software Foundation. Log4j is one of several Java Logging Frameworks.

Log4j in written in Java and also support cross platform and available with Apache License 2.0 License.

Log4j helps programmers output log statements from their programs. The log statements can be configured to be output to a variety of locations including the console, files and email. Log4j is a hierarchical logging utility which makes it possible to change the granularity at which log statements are output.

It is common practice to use the program's package structure as the basis for the hierarchy since the package structure of an application is inherently hierarchical and usually correlates to the hierarchy of the program code.

Log4j2.x changes the API and is no longer downward compatible to log4j1.x

Official Website:

Useful Links:

stackoverflow posts

See Also

Latest release log4j1: 1.2.17 released on August 5, 2015

Latest release log4j2: 2.13.3 released on 2020-05-10

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No appenders could be found for logger(log4j)?

I have put log4j to my buildpath, but I get the following message when I run my application: log4j:WARN No appenders could be found for logger (dao.hsqlmanager). log4j:WARN Please initialize the log4j system properly. log4j:WARN See…
maximus
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How to initialize log4j properly?

After adding log4j to my application I get the following output every time I execute my application: log4j:WARN No appenders could be found for logger (slideselector.facedata.FaceDataParser). log4j:WARN Please initialize the log4j system…
Janusz
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In log4j, does checking isDebugEnabled before logging improve performance?

I am using Log4J in my application for logging. Previously I was using debug call like: Option 1: logger.debug("some debug text"); but some links suggest that it is better to check isDebugEnabled() first, like: Option 2: boolean debugEnabled =…
Silent Warrior
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How to stop INFO messages displaying on spark console?

I'd like to stop various messages that are coming on spark shell. I tried to edit the log4j.properties file in order to stop these message. Here are the contents of log4j.properties # Define the root logger with appender…
Vishwas
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Configuring Log4j Loggers Programmatically

I am trying to use SLF4J (with log4j binding) for the first time. I would like to configure 3 different named Loggers that can be returned by a LoggerFactory which will log different levels and push the messages to different appenders: Logger 1…
IAmYourFaja
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log4j logging hierarchy order

What is the hierarchy of log4j logging? DEBUG INFO WARN ERROR FATAL Which one provides the highest logging which would be helpful to troubleshoot issues? Can any one provide the order or hierarchy in which logging take place from highest to…
Mike
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log4j: Log output of a specific class to a specific appender

I use log4j and would like to route the output of certain Loggers to specific files. I already have multiple appenders in place. Now, to make debugging easier, I want to tell log4j that the output generated by a specific class (e.g. foo.bar.Baz)…
gubrutz
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How to send a stacktrace to log4j?

Say you catch an exception and get the following on the standard output (like, say, the console) if you do a e.printStackTrace() : java.io.FileNotFoundException: so.txt at java.io.FileInputStream.(FileInputStream.java) at…
SyntaxT3rr0r
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log4j vs logback

We are using log4j behind a selfmade wrapper. We plan to use much more features of it now. Should we update to logback ? (I mean the framework not a facade like SLF4J)
TimmiB
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Where should I put the log4j.properties file?

I wrote a web service project using netbeans 6.7.1 with glassfish v2.1, put log4j.properties to the root dir of project and use: static Logger logger = Logger.getLogger(MyClass.class); in…
mono
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Java Logging vs Log4J

Is it still worth to add the log4j library to a Java 5 project just to log let's say some exceptions to a file with some nice rollover settings. Or will the standard util.logging facility do the job as well? What do you think?
Okami
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log4j configuration via JVM argument(s)?

What variables do I have to set/pass as arguments to the JVM to get log4j to run properly? And by properly I mean not complain and print to the console. Can I see a typical example? Note: I need to avoid creating a log4j.properties file in the…
jconlin
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If using maven, usually you put log4j.properties under java or resources?

Where should I put the log4j.properties file when using the conventional Maven directories?
user496949
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Dynamically Changing log4j log level

What are the different approaches for changing the log4j log level dynamically, so that I will not have to redeploy the application. Will the changes be permanent in those cases?
Ravi
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Is it worth to use slf4j with log4j2

I am not able to decide whether to use slf4j or not with log4j2. Based on online posts, does not look like it will have any performance hit but is it really required. Also these points rule in favor of log4j2: SLF4J forces your application to log…
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