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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:

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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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How to set the log level to DEBUG during Junit tests?

I am using SLF4J with LOG4J, and the configurations are usually in the log4j.properties, and it sets the log level to INFO. However during the tests I would like to set the logs to DEBUG. I can't see a way to automate this, neither to have something…
PedroD
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How to add Log4J2 appenders at runtime programmatically?

Is it possible to add Log4J2 appenders programmatically using the specifications from the XML configuration? I plan to define it all in the log4j2.xml and then pick appenders situationally like this (won't compile): if (arg[0].equals("log") ) { …
Brian Johnson
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Getting stacktrace in logger

I am using log4j to log my exceptions. I want to log whatever I get in e.printStackTrace(); My code looks like this: try { } catch(Exception e) { log.error("Exception is:::" + e); } But the content I get logged looks like this: 2012-02-02…
Geek
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How to get SLF4J "Hello World" working with log4j?

The "Hello World" example from SLF4J is not working for me. I guess this is because I added slf4j-log4 to my classpath. Should I configure log4j directly for the hello world to work? log4j:WARN No appenders could be found for logger…
ripper234
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log4j:WARN No appenders could be found for logger (running jar file, not web app)

First up - yes, I have read the multiple questions & answers on this topic, and can't get any of the solutions within those to help me. I'm not running Tomcat or JBoss and I don't have a web.xml file to change. I'm using Java 6.0 and…
Ina
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Using system environment variables in log4j xml configuration

Is it possible to reference system environment variables (as opposed to Java system properties) in a log4j xml configuration file? I'd like to be able to do something like: and have it get that from the system…
Derek Lewis
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Log Level per appender for a single Logger

Is it possible to configure different log levels for a single Logger based on the appender? I realize this is similar to this question, and this is as far as I had already got myself, but the problem with this is that the threshold applies to all…
Joel
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log4j2 xml configuration - Log to file and console (with different levels)

I want to do two things: Log to console with a certain log-level Log to file with another log-level Console logging seems to work just fine but the log file keeps beeing empty. This is my log4j2.xml
daker
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SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". in a Maven Project

I have a dependency for SLF4J. I am getting this error: SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for…
Kayser
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How to log Apache CXF Soap Request and Soap Response using Log4j?

I am using the Apache CXF Framework. Inside my client program, I need to log CXF SOAP Requests and SOAP Responses. When I used JaxWsProxyFactoryBean factory = new…
Pawan
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Making a log4j console appender use different colors for different threads

I am tracking down some concurrency issues and it would be very helpful to have the output lines from each thread in a different color when logging to a console. I am on OS X. Could this be done using a conversion pattern to output some control…
David Tinker
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Substituting parameters in log message and add a Throwable in Log4j 2

I am trying to log an exception, and would like to include another variable's value in the log message. Is there a Logger API that does this? logger.error("Logging in user {} with birthday {}", user.getName(), user.getBirthdayCalendar(),…
derrdji
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Log4J2 - assigning file appender filename at runtime

I have a log4j2.xml config file in the class path. One of the appenders is a File appender, and I would like to set the target file name at run time in the Java application. According to the docs I should be able to use a double "$" and a context…
user84756
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Log4j Implicit String Formatting

I am using log4j v1.2.14 for logging in my project and I am also using Java 7 String.format() to put variables in my output. Currently I am writing LOGGER.info(String.format("Your var is [%s] and you are [%s]", myVar, myVar1)); Is this really the…
Rossiar
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Is Log4j being abandoned in favor of Slf4j?

It seems that log4j has some class loading issues (among others) and it seems to me the trend is to move out of log4j toward slf4j. (Hibernate stopped using the first in favor of the latter) Is it true? What are the main issues in log4j that slf4j…
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