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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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Log4J: Strategies for creating Logger instances

I decided to use Log4J logging framework for a new Java project. I am wondering what strategy should I use for creating/managing Logger instances and why? one instance of Logger per class e.g. class Foo { private static final Logger log =…
Adrian
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Log4j: How to configure simplest possible file logging?

My story: I want to make a thing which is as simple as a simplest possible log4j logger that logs rows to a file. I have found several examples with some functionality, but not a basic, general one that really works, and not one with an explanation…
mico
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How to give environmental variable path for file appender in configuration file in log4j

I have a log4j.xml config file. and a RollingFileAppender to which I need to provide file path for storing logs. The problem is my code will be deployed on Unix machine as a runnable jar. So if I pass parameter something like…
Ankur Shanbhag
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Why log4j's Logger.getLogger() need pass a Class type?

I read some articles about how to use log4j. Most of them give below code as a beginning: Logger logger = Logger.getLogger("com.foo.Bar"); or Logger logger = Logger.getLogger(XXX.class); This will initialize the logger object.But my question is…
roast_soul
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How to configure log4j.properties for SpringJUnit4ClassRunner?

Suddenly this keeps happening during a JUnit test. Everything was working, I wrote some new tests and this error occured. If I revert it, it won't go away. Why is that? log4j:WARN No appenders could be found for logger…
user219882
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log4j: abbreviate/shorten package names

How would i abbreviate/shorten package names in log generated using log4j. i.e. instead of com.longpackage.anotherpackage.lastpackage.MyClass i want c.l.a.l.MyClass. I have seen this in Artifactory logs, but can't figure how to achieve this using…
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configure log4j to log to custom file at runtime

Can anyone please guide me as to how I can configure log4j to log to a specific file that I specify at run-time.The name and path of the log file are generated at run-time and the application must log to that particular file. Generally file appender…
Fell
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How can I get log4j to delete old rotating log files?

How can I get log4j to delete old rotating log files? I know I can set up automated jobs (cron for UNIX and scheduled task for Windows), but I want it cross platform, and I want it in our application's log configuration as a part of our…
skiphoppy
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Logging error to stderr and debug, info to stdout with log4j

I want to add logging to an application I am developing, using apache log4j. At this point I want to redirect all log messages for level INFO and lower (TRACE, DEBUG) to stdout and all other log messages from WARN and above (ERROR, FATAL) to…
Elvis
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How to create my own Appender in log4j?

I am new in log4j. Can anyone explain how to create my own Appender? i.e. how to implement the classes and interfaces and how to override it?
unknown
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log4j with timestamp per log entry

this is my log output INFO main digestemails - process inbox INFO main digestemails - checking for emails in c:\development\DCMail\email\KN-Source INFO main digestemails - digesting 003d01c95a7b_3446880_0202fea9@xxxx.com.eml INFO main digestemails -…
Setori
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How to Create a Custom Appender in log4j2?

As disscussed in this link : How to create a own Appender in log4j? For creating a custom appender in log4j 1.x we have to extend the AppenderSkeleton class and implements its append method. Similarly How we can create a custom appender in log4j2 as…
saurabh goyal
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How to enable Logger.debug() in Log4j

While trying to execute the following lines only the last two statements are displayed("Here is some ERROR" and "Here is some FATAL") and the first three statements are not displayed.I had just started to learn this topic, can anyone tell why is…
Hariharbalaji
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Log4j vulnerability - Is Log4j 1.2.17 vulnerable (was unable to find any JNDI code in source)?

With regard to the Log4j JNDI remote code execution vulnerability that has been identified CVE-2021-44228 - (also see references) - I wondered if Log4j-v1.2 is also impacted, but the closest I got from source code review is the JMS-Appender. The…
Ravindra HV
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Where is the correct location to put Log4j.properties in an Eclipse project?

Where in my Eclipse project should I add the log4j.properties file so that it will work as intended?
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