Add a universal j.u.l.LogManager implementation

[ppkarwasz]

As most developers are painfully aware redirecting java.util.logging to a decent logging framework is hard and:

1. it either requires to modify the java.util.logging.manager property very early in the lifecycle of an application, which is highly impractical,
2. or it requires the usage of a redirecting j.u.l.Handler like SLF4JBridgeHandler, which is less efficient. Log events traverse the entire JUL logging pipeline before being injected into SLF4J.

The best solution would be to force j.u.l.LogManager to use ServiceLoader, but I don't believe JDK-8262741 will be solved by OpenJDK any time soon.

What do you think about creating an org.slf4j.jul.LogManager implementation, whose only purpose would be to load some sort of LogManagerAdapter implementation via ServiceLoader? If such a solution were to be logging API-agnostic, many application runtime could hardcode the value of java.util.logging.manager in their shell scripts or main classes, while leaving the user the freedom to choose the JUL-to-X adapter of their choice.

[ppkarwasz]

I have provided an initial mock-up of such a universal j.u.l.LogManager implementation in ppkarwasz/slf4j/jul-manager.

[ceki]

@ppkarwasz Thank you for opening this discussion. I have not dabbled in LogManager in a long time. Could you please provide an example how the application runtime would hard code the value of java.util.logging.manager in their shell scripts or main classes?

[ppkarwasz]

The best example of setting the j.u.l.LogManager in a shell script is Tomcat's catalina.sh: it uses a LOGGING_MANAGER shell variable that sets up the java.util.logger.manager.

On the other hand Wildfly sets the java.util.logging.manager property in its code, e.g. org.jboss.modules.Main.

A rapid GitHub search for o.a.l.l.j.LogManager shows that many applications hardcode o.a.l.l.j.LogManager in their main class.

I would pretty much prefer if these 3 examples used the same implementation of j.u.l.LogManager, which would delegate calls of LogManager.getLogger() to the appropriate implementation retrieved from ServiceLoader (Tomcat's implementation of LogManager, JBoss Logging or Log4j API in these cases).