Spring and Logback

IoC, or DI definitely takes a perspective turnaround inside your head, but you get around it slowly.  I was playing around ways to integrate LogBack, and Spring – essentially around having Spring give me a pre-created instance of LogBack logger.

I searched around posts, but most people seem to be against using Spring just for substituting one-line of Logback (Logger log = LoggerFactory.getLogger("LogbackTest");) to get your logger.

I, on the other hand, was more interested in how to get Spring give me a LogBack logger instance without too much contrived hand-written code to achieve so. And with a bit of reading through Spring principles, documentation I found the way.

Essentially, when using Logback’s LoggerFactory you have access to only a single getLogger() factory method. This is static which makes things a bit different for what Spring would call a bean – a class providing constructor, getter, setter methods. To circumvent this non-bean style, Spring provides what you call as static initializers a.k.a substitutes for constructors, which allow you to call a static method in lieu of calling a constructor on an object.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
 "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>
 <bean id="bean1" class="org.slf4j.LoggerFactory" factory-method="getLogger">
 <constructor-arg value="LogbackTest" />
 </bean>
</beans>

Now, this bean1 can be used as a regular bean inside your class

ApplicationContext ctx = new FileSystemXmlApplicationContext("logbacktest.xml");
 Logger log = (Logger) ctx.getBean("bean1");

 log.debug("This is my first message");
 log.info("How about this information message");

Throw in a logback.xml in your classpath, and viola you have a nice Spring injected dependency – log in your code, while still using Logback!