dubbo源码分析- 日志实现-白红宇

dubbo源码分析- 日志实现

阅读量：6916 次

发布时间：2019-06-27

本文共 8518 字，大约阅读时间需要 28 分钟。

## 使用

private static final Logger logger = LoggerFactory.getLogger(ZookeeperRegistry.class);

原理

dubbo的日志实现机制比较简单通过LoggerFactory来初始化具体的实现方式，Logger的实现通过loggerAdapter适配，LoggerAdapter接口使用@SPI注解，表示其使用的是dubbo的spi机制扩展，loggerAdapter的实现类有4种log4j,sl4j,jcl,jdk.

//// Source code recreated from a .class file by IntelliJ IDEA// (powered by Fernflower decompiler)//package com.alibaba.dubbo.common.logger;import com.alibaba.dubbo.common.extension.SPI;import java.io.File;@SPIpublic interface LoggerAdapter {    Logger getLogger(Class
     var1);    Logger getLogger(String var1);    Level getLevel();    void setLevel(Level var1);    File getFile();    void setFile(File var1);}

Log4jLoggerAdapter实现如下

//// Source code recreated from a .class file by IntelliJ IDEA// (powered by Fernflower decompiler)//package com.alibaba.dubbo.common.logger.log4j;import com.alibaba.dubbo.common.logger.LoggerAdapter;import java.io.File;import java.util.Enumeration;import org.apache.log4j.Appender;import org.apache.log4j.FileAppender;import org.apache.log4j.Level;import org.apache.log4j.LogManager;import org.apache.log4j.Logger;public class Log4jLoggerAdapter implements LoggerAdapter {    private File file;    public Log4jLoggerAdapter() {        try {            Logger logger = LogManager.getRootLogger();            if (logger != null) {                Enumeration
    
      appenders = logger.getAllAppenders();                if (appenders != null) {                    while(appenders.hasMoreElements()) {                        Appender appender = (Appender)appenders.nextElement();                        if (appender instanceof FileAppender) {                            FileAppender fileAppender = (FileAppender)appender;                            String filename = fileAppender.getFile();                            this.file = new File(filename);                            break;                        }                    }                }            }        } catch (Throwable var6) {            ;        }    }    private static Level toLog4jLevel(com.alibaba.dubbo.common.logger.Level level) {        if (level == com.alibaba.dubbo.common.logger.Level.ALL) {            return Level.ALL;        } else if (level == com.alibaba.dubbo.common.logger.Level.TRACE) {            return Level.TRACE;        } else if (level == com.alibaba.dubbo.common.logger.Level.DEBUG) {            return Level.DEBUG;        } else if (level == com.alibaba.dubbo.common.logger.Level.INFO) {            return Level.INFO;        } else if (level == com.alibaba.dubbo.common.logger.Level.WARN) {            return Level.WARN;        } else {            return level == com.alibaba.dubbo.common.logger.Level.ERROR ? Level.ERROR : Level.OFF;        }    }    private static com.alibaba.dubbo.common.logger.Level fromLog4jLevel(Level level) {        if (level == Level.ALL) {            return com.alibaba.dubbo.common.logger.Level.ALL;        } else if (level == Level.TRACE) {            return com.alibaba.dubbo.common.logger.Level.TRACE;        } else if (level == Level.DEBUG) {            return com.alibaba.dubbo.common.logger.Level.DEBUG;        } else if (level == Level.INFO) {            return com.alibaba.dubbo.common.logger.Level.INFO;        } else if (level == Level.WARN) {            return com.alibaba.dubbo.common.logger.Level.WARN;        } else {            return level == Level.ERROR ? com.alibaba.dubbo.common.logger.Level.ERROR : com.alibaba.dubbo.common.logger.Level.OFF;        }    }    public com.alibaba.dubbo.common.logger.Logger getLogger(Class
      key) {        return new Log4jLogger(LogManager.getLogger(key));    }    public com.alibaba.dubbo.common.logger.Logger getLogger(String key) {        return new Log4jLogger(LogManager.getLogger(key));    }    public com.alibaba.dubbo.common.logger.Level getLevel() {        return fromLog4jLevel(LogManager.getRootLogger().getLevel());    }    public void setLevel(com.alibaba.dubbo.common.logger.Level level) {        LogManager.getRootLogger().setLevel(toLog4jLevel(level));    }    public File getFile() {        return this.file;    }    public void setFile(File file) {    }}

最重要的是LoggerFactory类

//// Source code recreated from a .class file by IntelliJ IDEA// (powered by Fernflower decompiler)//package com.alibaba.dubbo.common.logger;import com.alibaba.dubbo.common.extension.ExtensionLoader;import com.alibaba.dubbo.common.logger.jcl.JclLoggerAdapter;import com.alibaba.dubbo.common.logger.jdk.JdkLoggerAdapter;import com.alibaba.dubbo.common.logger.log4j.Log4jLoggerAdapter;import com.alibaba.dubbo.common.logger.slf4j.Slf4jLoggerAdapter;import com.alibaba.dubbo.common.logger.support.FailsafeLogger;import java.io.File;import java.util.Iterator;import java.util.Map.Entry;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ConcurrentMap;public class LoggerFactory {    //缓存Classs名称和Logger具体实现映射    private static final ConcurrentMap
    
      LOGGERS = new ConcurrentHashMap();	//当前LoggerAdapter实现 volatile保证内存可见性    private static volatile LoggerAdapter LOGGER_ADAPTER;    private LoggerFactory() {    }	//通过spi机制 得到LoggerAdapter实现    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());			//此处设置LoggerAdapter实现            LOGGER_ADAPTER = loggerAdapter;			//此处遍历LOGGERS缓存，设置value值（FailsafeLogger类）的成员变量Logger实现            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 Level getLevel() {        return LOGGER_ADAPTER.getLevel();    }    public static void setLevel(Level level) {        LOGGER_ADAPTER.setLevel(level);    }    public static File getFile() {        return LOGGER_ADAPTER.getFile();    }	//当调用LoggerFactory.getLogger(ZookeeperRegistry.class)方法时，触发jvm加载当调用LoggerFactory类，从而执行static代码块。	//首先获取系统变量，如果指定了实现方式 则设置LoggerAdapter成员变量	//如果没指定，按照Log4jLoggerAdapter，Slf4jLoggerAdapter，JclLoggerAdapter，JdkLoggerAdapter顺序依次设置LoggerAdapter实现，	//比如设置Log4jLoggerAdapter时 没有引入对应依赖，则抛ClassNotFound依次，接着尝试设置其他LoggerAdapter    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()));                    }                }            }        }    }}

转载于:https://my.oschina.net/odetteisgorgeous/blog/3018719

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