Log4J

Log4J is the API with which we can add Log information for a application.
Though in development environments,we can have the tools to debug the code directly,
In production environment,Logs are the only source of information to analyse any issue/bug.
Logs can be used to debug,provided the information is logged in a proper way.

Simple Hello World Spring application with Logger.

There are Different log levels provided by API,and they can be configured in log4j.xml.
1.DEBUG
2.INFO
3.WARN
4.ERROR
5.FATAL
6.OFF

Suppose a log level INFO is enabled , all the levels below INFO will be enabled. i.e. levels
WARN,ERROR,FATAL,OFF.