SLF4J 门面日志框架源码探索 | 京东云技术团队

        <dependency>            <groupId>org.slf4j</groupId>            <artifactId>slf4j-api</artifactId>            <version>1.7.30</version>        </dependency>

public class HelloSlf4j {
    public static void main(String[] args) {        Logger logger = LoggerFactory.getLogger(HelloSlf4j.class);        logger.info("Hello World info");    }}

private final static void bind() {        try {            Set<URL> staticLoggerBinderPathSet = null;            // skip check under android, see also            // http://jira.qos.ch/browse/SLF4J-328            if (!isAndroid()) {                staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();                reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);            }            // the next line does the binding            StaticLoggerBinder.getSingleton();            INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION;            reportActualBinding(staticLoggerBinderPathSet);        } catch (NoClassDefFoundError ncde) {            String msg = ncde.getMessage();            if (messageContainsOrgSlf4jImplStaticLoggerBinder(msg)) {                INITIALIZATION_STATE = NOP_FALLBACK_INITIALIZATION;                Util.report("Failed to load class "org.slf4j.impl.StaticLoggerBinder".");                Util.report("Defaulting to no-operation (NOP) logger implementation");                Util.report("See " + NO_STATICLOGGERBINDER_URL + " for further details.");            } else {                failedBinding(ncde);                throw ncde;            }        } catch (java.lang.NoSuchMethodError nsme) {            String msg = nsme.getMessage();            if (msg != null && msg.contains("org.slf4j.impl.StaticLoggerBinder.getSingleton()")) {                INITIALIZATION_STATE = FAILED_INITIALIZATION;                Util.report("slf4j-api 1.6.x (or later) is incompatible with this binding.");                Util.report("Your binding is version 1.5.5 or earlier.");                Util.report("Upgrade your binding to version 1.6.x.");            }            throw nsme;        } catch (Exception e) {            failedBinding(e);            throw new IllegalStateException("Unexpected initialization failure", e);        } finally {            postBindCleanUp();        }    }

            ClassLoader loggerFactoryClassLoader = LoggerFactory.class.getClassLoader();            Enumeration<URL> paths;            if (loggerFactoryClassLoader == null) {                paths = ClassLoader.getSystemResources(STATIC_LOGGER_BINDER_PATH);            } else {                paths = loggerFactoryClassLoader.getResources(STATIC_LOGGER_BINDER_PATH);            }

        <dependency>            <groupId>ch.qos.logback</groupId>            <artifactId>logback-classic</artifactId>            <version>1.2.3</version>        </dependency>

        <dependency>            <groupId>org.apache.logging.log4j</groupId>            <artifactId>log4j-slf4j-impl</artifactId>            <version>2.9.1</version>        </dependency>

SLF4J: Found binding in [jar:file:/D:/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]SLF4J: Found binding in [jar:file:/D:/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.9.1/log4j-slf4j-impl-2.9.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]18:19:43.521 [main] INFO com.cj.HelloSlf4j - Hello World info

SLF4J: Class path contains multiple SLF4J bindings.SLF4J: Found binding in [jar:file:/D:/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.9.1/log4j-slf4j-impl-2.9.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]SLF4J: Found binding in [jar:file:/D:/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console. Set system property 'log4j2.debug' to show Log4j2 internal initialization logging.

private static List<SLF4JServiceProvider> findServiceProviders() {        ServiceLoader<SLF4JServiceProvider> serviceLoader = ServiceLoader.load(SLF4JServiceProvider.class);        List<SLF4JServiceProvider> providerList = new ArrayList();        Iterator var2 = serviceLoader.iterator();
        while(var2.hasNext()) {            SLF4JServiceProvider provider = (SLF4JServiceProvider)var2.next();            providerList.add(provider);        }
        return providerList;     }

        Logger logger = LoggerFactory.getLogger(HelloSlf4j.class);        logger.info("Hello World info");