Where to place log4j.xml

问题:

How can we specify were log4j has to look at when trying to find its xml configuration file ?

It seems that by default, log4j looks into the root of a class folder, I can say that using the debug log4j functionality and running my application from the IDE.

However, I don't have any class folder in my jar anymore. And the log4j.xml file is at the root of the jar.

I have already tried to set the option -Dlog4j.configuration=log4j.xml but it doesn't work.

Here is the global structure of my application at the moment :

• com
• lib
• meta-inf
• log4j.xml

回答1:

It finds the log4j.xml using the CLASSPATH. If log4j doesn't find any config file, it will send an error to the console. If you don't see any such error then it is likely that it is finding a config file which may not be the one you are editing. There is a command-line option to force Log4J to report the path of the config file it is using.

From http://wiki.apache.org/logging-log4j/Log4jConfigurationHelp

If you run with "-Dlog4j.debug" then log4j will print out info to standard output telling how it is trying to configure itself. Looking through that will tell you where it is looking for the config file.

回答2:

Suppose your log4j configuration is outside the source tree. If it can't find your configuration file, help it with:

-Dlog4j.configuration=file:///your/path/log4j.xml

Note the qualifier file:///. It won't work without.

回答3:

I don't have any error

So log4j is finding your configuration, otherwise you would get:

log4j:WARN No appenders could be found for logger ().
log4j:WARN Please initialize the log4j system properly.

Also:

The log are just printed out on the console

So that means that you probably need to define a file appender, like FileAppender or RollingFileAppender. The "Configuration" section on the short intro has a few examples.

回答4:

You can use:

DOMConfigurator.configure(log4jConfigurationFilename);

and specify the location if it is other than the root!

回答5:

May be this is very old question, but for me the answer was here https://logging.apache.org/log4j/2.x/manual/configuration.html

As per above link, Apache log search in classpath for the log4j2.xml files in a specific order as below

1. Log4j will inspect the "log4j.configurationFile" system property and, if set, will attempt to load the configuration using the ConfigurationFactory that matches the file extension.
2. If no system property is set the properties ConfigurationFactory will look for log4j2-test.properties in the classpath.
3. If no such file is found the YAML ConfigurationFactory will look for log4j2-test.yaml or log4j2-test.yml in the classpath.
4. If no such file is found the JSON ConfigurationFactory will look for log4j2-test.json or log4j2-test.jsn in the classpath. If no such file is found the XML ConfigurationFactory will look for log4j2-test.xml in the classpath.
5. If a test file cannot be located the properties ConfigurationFactory will look for log4j2.properties on the classpath.
6. If a properties file cannot be located the YAML ConfigurationFactory will look for log4j2.yaml or log4j2.yml on the classpath.
7. If a YAML file cannot be located the JSON ConfigurationFactory will look for log4j2.json or log4j2.jsn on the classpath.
8. If a JSON file cannot be located the XML ConfigurationFactory will try to locate log4j2.xml on the classpath.
9. If no configuration file could be located the DefaultConfiguration will be used. This will cause logging output to go to the console.

回答6:

Do not worry about where to put it. Just run your project, say in eclipse, log4j will throw an exception, telling you where it was looking. Then you can put it there.

Once you get it working, you will also figure out how to change that, as you understand the logic.