Why its better to use SLF4j over Log4j for logging in Java?

How logging abstraction can help you in long run

Every Java programmers know that logging is critical for any Java application, especially server-side application, and many of them are already familiar with various logging libraries e.g. java.util.logging, Apache log4j, logback, but if you don't know about SLF4J, Simple logging facade for Java,  then it's time to learn and use SLF4J in your project.

In the past, I have shared Java Multithreading questions, Java Serialization questions, System Design interview questions Producer Consumer Pattern, and Enum Interview Questions and In this post, we will see Why its better to use SLF4j over Log4j for logging in Java? which is also a logging best practice in Java.

Contrary to all those logging libraries, there is a major difference between them and SLF4J.

SLF4J or Simple logging Facade for Java is not really a logging implementation, instead, it's an abstraction layer, which allows you to use any logging library in the back-end. 

If you are writing API or utility library, which can be used internally or externally, then you really don't want that any client, which uses your library, should also stick with your choice of logging library. 

Suppose, if a project is already using log4j, and you included a library say Apache Active MQ, which has dependency on logback, another logging library, then you need to include them as well, but if Apache Active MQ uses SL4J, you can continue with your logging library, without pain of adding and maintaining new logging framework.

In short, SLF4J makes your code independent of any particular logging API, which is a good thing for public API developers. 

Though idea of abstracting logging library is not new and Apache commons logging is already using it, but now SLF4J is quickly becoming an standard for logging in Java world. 

By the way, if you are new to the Java world then I highly recommend you to go through a comprehensive Java course like The Complete Java Masterclass by Tim Buchalaka and his team to learn essential Java concepts like Enum and Generics.

And, if you are preparing for Java interviews, you can also checkout my books, Grokking the Java Interview and Grokking the Spring Boot, where I have shared frequently asked Java interview questions. You can also use code friends50 to get 50% discount for next few days.

Now, let's see couple of more reasons and code to use SLF4J over log4j, logback or java.util.logging.