How to initialize log4j properly?

Question

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 (slideselec         


        

Answer 1

To enable -Dlog4j.debug, I go to System, Advanced system settings, Environment variables and set system variable _JAVA_OPTIONS to -Dlog4j.debug.

Answer 2

The fix for me was to put "log4j.properties" into the "src" folder.

Answer 3

Find a log4j.properties or log4j.xml online that has a root appender, and put it on your classpath.

### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.SimpleLayout
log4j.rootLogger=debug, stdout

will log to the console. I prefer logging to a file so you can investigate afterwards.

log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.maxFileSize=100KB
log4j.appender.file.maxBackupIndex=5
log4j.appender.file.File=test.log
log4j.appender.file.threshold=debug
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n
log4j.rootLogger=debug,file

although for verbose logging applications 100KB usually needs to be increased to 1MB or 10MB, especially for debug.

Personally I set up multiple loggers, and set the root logger to warn or error level instead of debug.

Answer 4

You can set the location of your log4j.properties from inside your java app by using:

org.apache.log4j.PropertyConfigurator.configure(file/location/log4j.properties)

More information is available here: https://logging.apache.org/log4j/1.2/manual.html

Answer 5

I just did this and the issue was fixed.

Followed the below blog

https://intellij-support.jetbrains.com/hc/en-us/community/posts/206875685-How-to-fix-log4j-WARN-console-messages-when-running-an-Application-inside-IntelliJ-Idea

But here he says like below

To fix that just enter the following log4j.resources file into main/resources folder of your project

instead of creating log4j.resources, create log4j.properties. Right Click on Resource in IntelliJ -> New -> Resource Bundle - Just name it as log4j

Answer 6

Try to set debug attribut in log4j:configuration node to true.

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

It prints out information as the configuration file is read and used to configure the log4j environment. You may be got more details to resolve your problem.