Coder’s Corner: Using Log4j in a LibGdx project in Intellij – Gradle hiccup

Apparently stuxnet managed to hybridize in a way such that it’s taken Josh out for the foreseeable future. Either that or he succumbed to snowcrash. In any event, that means that Rho-Bot and I will be conquering our weekly blog for the foreseeable future. And starting our new and likely recurring segment: Coder’s Corner.

Earlier this week I was setting up our new project (no, we’re not going to squeal on what it is yet), and I wanted to use the Log4j libraries. My primary motivation for doing so is that I like data and, if I’m not the one doing the testing, I usually get incomplete descriptions of bugs back. Since libgdx’s built in logging only outputs to the console we need some way to create actual log files ergo Log4j. I’ve used these libraries in our earlier projects with no problems. But last week I started using Intellij as my IDE. This time, however, after I dropped the libraries and my config file into the same location as the last project and I got this error:

log4j error
ERROR StatusLogger No log4j2 configurationfile found. Using default configuration: logging only errors to the console.

I know what you’re computing ‘ACMU you forgot to add ?*.xml to the resource patterns in your compiler settings. As it happens, 0) I did not forget to do that, and 1) as I found out the next day it’s not strictly necessary to do that for Log4j anyway.
With that most obvious source of my difficulties out of the way I clicked over to the Log4j manual and it says

“If a JSON file cannot be located the XML ConfigurationFactory will try to locate log4j2.xml on the classpath.” 

So you’d think that if my project structure looks like this:

project structure
Whatever the next project is it’s safe to say it’s both bad and angry

the library would find a configuration file acceptable and use it. No dice (Did you processor that pun?). So I spent a few hours on stackexchange making no progress. Then, through some fluke, I read the Log4j configuration page again and realized that a line up at the top says,

“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.”

Alright so we’ll just got to Run->Edit Configurations, set our system property like this:

configuration options

Drop the config file into your working directory and voila, Log4j is configured.

The next morning when I got to work it occurred to me that a work project was using Log4j too. I had just started using Intellij at work too, and I didn’t remember having any configuration issues, so I did a little digging. I went looking for the project’s log4j2.xml file and found it sitting in the /src/ directory and I hadn’t even marked *.xml as a resource file type.

Which leads to the question, “What are the differences between these two projects?”. Well, at home I set up a libgdx project using gradle for dependency management; at work I just write code with no dependency management – because enterprise applications are boring. So, an alternate (and probably better) solution than the one I found is to include the Log4j configuration file as a resource in the file. And no I’m not going to tell you how to do that. In the words of many a professor and textbook: it’s left as an exercise for the reader.

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