How does slf4j bind to implementation? Does it really do so during compile time?

Question

In the documentation for slf4j it says that the binding happens during complie time:

\"SLF4J does not rely on any special class loader machinery. In fact, each SLF4J bi

Answer 1

Here is the source code of slf4j. Slf4j will find all the class in the class path whose path is "org/slf4j/impl/StaticLoggerBinder.class". And if there are more than one, jvm will pick up only one randomly.For more detail you can see here:http://www.slf4j.org/codes.html#multiple_bindings

// We need to use the name of the StaticLoggerBinder class, but we can't
// reference
// the class itself.

private static String STATIC_LOGGER_BINDER_PATH = "org/slf4j/impl/StaticLoggerBinder.class";

static Set findPossibleStaticLoggerBinderPathSet() {
 // use Set instead of list in order to deal with bug #138
 // LinkedHashSet appropriate here because it preserves insertion order
 // during iteration
    Set staticLoggerBinderPathSet = new LinkedHashSet(); 
    try {
        ClassLoader loggerFactoryClassLoader = LoggerFactory.class.getClassLoader();
        Enumeration paths;
        if (loggerFactoryClassLoader == null) {
            paths = ClassLoader.getSystemResources(STATIC_LOGGER_BINDER_PATH);
        } else {
            paths = loggerFactoryClassLoader.getResources(STATIC_LOGGER_BINDER_PATH);
        }
        while (paths.hasMoreElements()) {
            URL path = paths.nextElement();
            staticLoggerBinderPathSet.add(path);
        }
    } catch (IOException ioe) {
        Util.report("Error getting resources from path", ioe);
    }
    return staticLoggerBinderPathSet;
}