Creating an application logger

[Redan Hassoun]

Hi,

I have built a Java Spring Boot application, and I am using "log4j" for logging,
And in order to use the logger class, I do this:

private Logger logger = LoggerFactory.getLogger(Example.class);

But I think this is a mistake because I better encapsulate away all the "log4j" stuff inside a logger class and inject that class to other classes.

For example, I need to be able to do this:

@RestController
@RequestMapping("/api/example")
public class ExampleController{
       private AppLogger<ExampleController> logger;
       public ExampleController(AppLogger<ExampleController> logger) {
           this.logger = logger;
       }
       ...
}

This logger should print the "ExampleController" class name on the logs.

How can I implement the "AppLogger" so that it gets the correct class name without having to pass it through the constructor?

[Redan Hassoun]

Found a solution in this article:
https://dzone.com/articles/logger-injection-with-springs-injectionpoint

[Himai Minh]

You may want to try org.slf4j.Logger and org.slf4j.LoggerFactory.
The code should be:

 Logger logger = LoggerFactory.getLogger(Example.class); 

[Redan Hassoun]

Himai Minh wrote:You may want to try org.slf4j.Logger and org.slf4j.LoggerFactory.
The code should be:

 Logger logger = LoggerFactory.getLogger(Example.class); 

I am already using log4j, but I prefer injecting it instead of creating it manually.
One of the reasons is unit/integration testing, if I want to test my code, I want to be able to inject a mock logger instead of writing real logs.

[Ron McLeod]

Its easy to do with JakartaEE/MicroProfile using CDI - not sure how to do something similar with Spring.

import javax.enterprise.inject.Default;
import javax.enterprise.inject.Produces;
import javax.enterprise.inject.spi.InjectionPoint;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class LoggingProvider {
	@Produces
	@Default
	public Logger produceLogger(InjectionPoint injectionPoint) {
		return LoggerFactory.getLogger(injectionPoint.getMember().getDeclaringClass().getName());
	}
}

import javax.enterprise.context.Dependent;
import javax.inject.Inject;

import org.slf4j.Logger;

@Dependent
public class MyClass {
	@Inject
	Logger logger;
	
	...
	
}