dubbo的LoggerAdapter

项目使用spring+dubbo+zookeeper

因为需要跟踪dubbo服务调用方ip，使用在<dubbo:service />接口上加accesslog="true"的方法来记录访问log。

但是发现在使用log4j的项目中是可以的，在使用logback的项目中却不行。access日志的记录是通过AccessLogFilter来实现的，通过debug发现在使用logback的项目中记录log时的Logger对象是Log4jLogger对象。

 

public class LoggerFactory {
    private static volatile LoggerAdapter LOGGER_ADAPTER;
    private static final ConcurrentMap<String, FailsafeLogger> LOGGERS = new ConcurrentHashMap();

    private LoggerFactory() {
    }

    public static void setLoggerAdapter(String loggerAdapter) {
        if(loggerAdapter != null && loggerAdapter.length() > 0) {
            setLoggerAdapter((LoggerAdapter)ExtensionLoader.getExtensionLoader(LoggerAdapter.class).getExtension(loggerAdapter));
        }

    }

    public static void setLoggerAdapter(LoggerAdapter loggerAdapter) {
        if(loggerAdapter != null) {
            Logger logger = loggerAdapter.getLogger(LoggerFactory.class.getName());
            logger.info("using logger: " + loggerAdapter.getClass().getName());
            LOGGER_ADAPTER = loggerAdapter;
            Iterator i$ = LOGGERS.entrySet().iterator();

            while(i$.hasNext()) {
                Entry entry = (Entry)i$.next();
                ((FailsafeLogger)entry.getValue()).setLogger(LOGGER_ADAPTER.getLogger((String)entry.getKey()));
            }
        }

    }

    public static Logger getLogger(Class<?> key) {
        FailsafeLogger logger = (FailsafeLogger)LOGGERS.get(key.getName());
        if(logger == null) {
            LOGGERS.putIfAbsent(key.getName(), new FailsafeLogger(LOGGER_ADAPTER.getLogger(key)));
            logger = (FailsafeLogger)LOGGERS.get(key.getName());
        }

        return logger;
    }

    public static Logger getLogger(String key) {
        FailsafeLogger logger = (FailsafeLogger)LOGGERS.get(key);
        if(logger == null) {
            LOGGERS.putIfAbsent(key, new FailsafeLogger(LOGGER_ADAPTER.getLogger(key)));
            logger = (FailsafeLogger)LOGGERS.get(key);
        }

        return logger;
    }

    public static void setLevel(Level level) {
        LOGGER_ADAPTER.setLevel(level);
    }

    public static Level getLevel() {
        return LOGGER_ADAPTER.getLevel();
    }

    public static File getFile() {
        return LOGGER_ADAPTER.getFile();
    }

    static {
        String logger = System.getProperty("dubbo.application.logger");
        if("slf4j".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new Slf4jLoggerAdapter()));
        } else if("jcl".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new JclLoggerAdapter()));
        } else if("log4j".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new Log4jLoggerAdapter()));
        } else if("jdk".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new JdkLoggerAdapter()));
        } else {
            try {
                setLoggerAdapter((LoggerAdapter)(new Log4jLoggerAdapter()));
            } catch (Throwable var6) {
                try {
                    setLoggerAdapter((LoggerAdapter)(new Slf4jLoggerAdapter()));
                } catch (Throwable var5) {
                    try {
                        setLoggerAdapter((LoggerAdapter)(new JclLoggerAdapter()));
                    } catch (Throwable var4) {
                        setLoggerAdapter((LoggerAdapter)(new JdkLoggerAdapter()));
                    }
                }
            }
        }

    }
}

 

 

进一步了解dubbo的日志系统，dubbo内部的日志输出都是通过LoggerFactory来获取Logger然后进行输出。

Logger接口有JclLogger（commons.logging）、JdkLogger（java.util.logging.Logger）、Log4jLogger、Slf4jLogger几种实现。Logger对象又是通过LoggerAdapter和第三方日志框架进行对接并直接创建，于是又对应几种LoggerAdapter：JclLoggerAdapter、JDKLoggerAdapter、Log4jLoggerAdapter、SLF4JLoggerAdapter。

通过这段代码

 

static {
        String logger = System.getProperty("dubbo.application.logger");
        if("slf4j".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new Slf4jLoggerAdapter()));
        } else if("jcl".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new JclLoggerAdapter()));
        } else if("log4j".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new Log4jLoggerAdapter()));
        } else if("jdk".equals(logger)) {
            setLoggerAdapter((LoggerAdapter)(new JdkLoggerAdapter()));
        } else {
            try {
                setLoggerAdapter((LoggerAdapter)(new Log4jLoggerAdapter()));
            } catch (Throwable var6) {
                try {
                    setLoggerAdapter((LoggerAdapter)(new Slf4jLoggerAdapter()));
                } catch (Throwable var5) {
                    try {
                        setLoggerAdapter((LoggerAdapter)(new JclLoggerAdapter()));
                    } catch (Throwable var4) {
                        setLoggerAdapter((LoggerAdapter)(new JdkLoggerAdapter()));
                    }
                }
            }
        }

    }

 

 

可以发现在未指定dubbo.application.logger，也就是默认情况下，dubbo会优先选用log4j，而logback是和slf4j集成的，这就说明了为何在使用logback时没有日志输出了。

解决的办法就是指定dubbo.application.logger参数为slf4j：

1、在jvm启动时添加此参数

-Ddubbo.application.logger=slf4j

 

2、在LoggerFactory被classloader加载之前通过编码方式指定

System.setProperty("dubbo.application.logger","slf4j");