如何配置Log4J2

Question

I have spent a couple hours now trying to figure this out and am at a complete loss. I find the new configuration process unnecessarily complex.

I have a Servlet with a web.xml file with the following:

<context-param>
    <param-name>log4jConfiguration</param-name>
    <param-value>file:///etc/myApp/log4j2.xml</param-value>
</context-param>

It doesn't seem to have any effect. I am using Tomcat 7.0.42, and I have removed all references to log4j*.jar in the catalina.properties file. The logs in my app are still being sent, but they are just being sent to System.out with none of the formatting I specified.

So, I tried to just do it by hand on my own:

InputStream in =
    new FileInputStream(new File("/etc/myApp/log4j2.xml"));
ConfigurationSource source = new ConfigurationSource(in);
ConfigurationFactory factory = new XMLConfigurationFactory();
Configuration configuration = factory.getConfiguration(source);
LoggerContext context = (LoggerContext) LogManager.getContext();
context.start(configuration);
context.updateLoggers();

Logger.getLogger("Test").log(Level.INFO, "This is a logging message.");

First, this seems entirely convoluted. Clearly there exists some code that will search for different files and assume file types based on their extensions via the "log4jConfiguration" property, so why isn't there a LogManger.reconfigure(String) that has the same effect?

Second, this has no effect either. Again, the log is printed to System.out, and none of the requested formatting is being done.

Here is the contents of my log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="DEBUG">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>

    <File name="LogFile" fileName="/var/log/myApp/myApp.log">
      <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} %p %c{1.} [%t] %m%n"/>
    </File>
  </Appenders>
  <Loggers>
    <Root level="DEBUG">
      <AppenderRef ref="Console" level="DEBUG"/>
      <AppenderRef ref="LogFile" level="DEBUG"/>
    </Root>
  </Loggers>
</Configuration>

The output in both cases comes out something like:

Dec 03, 2013 6:06:45 PM test.Test main
INFO: This is a logging message.

Thanks in advance,

John

EDIT: This is actually working. It appears that I was missing, "log4j-jcl-2.0-beta9.jar". Remko Popma's answer works as well, if the "context-param" above is not working.

Answer 1

There are many possible scenarios with webapp logging, which makes configuration more complex than the ideal. Putting the log4j2 jars and the config file in your webapp's classpath should work. Did you see the manual page for log4j2 use in web apps? If the issue remains, please file a log4j2 jira ticket.

Answer 2

The LoggerContext already has a method setConfigLocation that takes in a URI as parameter. It baffles me why there isn't a similar method that takes an InputStream as parameter. Instead we have to deal with the most convoluted and messy way of loading our log4j2.xml that is not on the classpath.