LoggerFactory

LoggerFactory

A well developed application deserves to log various information, so that when a problem occurs, it makes the life easier for both the end-user and the developer.

Android comes with a built-in very light logging system though the android.util.Log class. It is a good thing that it is light, because it is going to be running on small footprint devices, but it is a bit a pity that the developer cannot find back something which looks like the Java java.util.logging package or the Apache Log4J framework.

Log: a very simple logging interface

This is the reason why we have introduced a minor component available though the LoggerFactory class: it exposes two simple getInstance() methods, which return a Logger interface implementation.

The Logger class is the one that should be used for logging, just like on the Android android.util.Log class. In order to use it:

1. set properly the LoggerFactory.logLevel variable, so that your application only outputs logs from a certain level ;
2. just create a static instance of Logger by using the LoggerFactory.getInstance() factory (the parameter is usually the enclosing class, or a string): this parameter will be considered as the traditional Log4J category,
3. in the code where a logging, us the Logger logging methods ; if you want to optimize further, do not forget to surround your logging statement by a Logger.isXXXEnabled(), just like you would with Log4J.

So as to make this logging component even more flexible, we should let the developer chose the Logger interface implementation to use, in the future: just ask, and we will work on that.

Key benefits of using the "LoggerFactory"

• The Logger interface exposes some isXXXEnabled() methods, which enables to prevent from preparing a logging string for nothing if the logging level does not require it.
• When running some code on a pure Java environment on which the Android runtime is not available, if you define the Java system property droid4me.logging to value false, then the standard output and the standard error output will be used to issue the logs (actually, it will use the NativeLogger implementation).
• When logging, you do not need to specify a tag, and the log output uses the Logger declared category as a tag.
• The whole framework uses that logging facility, hence you get logs in a consistent way. For instance, you can look in adb the logs for the tags "Smartable", "Persistence", "BitmapDownloader", "ActivityController", "SmartApplication" ...

When submitting your application under production, do not forget to increase the logging trigger level through the LoggerFactory.logLevel variable!