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Donald_Draper:
Donald_Draper 写道刘落落cici 写道能给我发一 ...
DatagramChannelImpl 解析三(多播) -
Donald_Draper:
刘落落cici 写道能给我发一份这个类的源码吗Datagram ...
DatagramChannelImpl 解析三(多播) -
lyfyouyun:
请问楼主,执行消息发送的时候,报错:Transport sch ...
ActiveMQ连接工厂、连接详解 -
ezlhq:
关于 PollArrayWrapper 状态含义猜测:参考 S ...
WindowsSelectorImpl解析一(FdMap,PollArrayWrapper) -
flyfeifei66:
打算使用xmemcache作为memcache的客户端,由于x ...
Memcached分布式客户端(Xmemcached)
java中volatile关键字的含义:http://www.cnblogs.com/aigongsi/archive/2012/04/01/2429166.html
Java transient关键字使用小记:http://www.cnblogs.com/lanxuezaipiao/p/3369962.html
Log4j初始化详解:http://donald-draper.iteye.com/blog/2332385
Log4j日志输出详解 :http://donald-draper.iteye.com/blog/2332395
slf4j + Log4j的使用:http://donald-draper.iteye.com/blog/2332407
上一篇简单学习了Log4j的使用,今天来看一下,日志初始化,
我们就从下面这一句来看:
查看Logger
来看LogManager的getLogger方法
//LogManager
//NOPLoggerRepository
//NOPLogger
而Logger继承Category
//Category
//Level
//Priority
我们在回到LogManager加载log4j属性文件,关键在这一句
这个LoggerRepository实际为NOPLoggerRepository
来看log4j.properties属性文件解析
//PropertyConfigurator
//配置RootCategory,rootLogger,appenders
来看 OptionConverter.findAndSubst
//返回key对应的属性
//NOPLoggerRepository,获取rootLogger
//PropertyConfigurator
//根据appenderName解析Appender
//OptionConverter.instantiateByKey
//PropertyConfigurator
// protected Hashtable registry;HashTable<String,Appender>
//将Appender放入registry
下面我们来看看logger.addAppender,都做了些什么
//AppenderAttachableImpl
总结:
从以上我们可以看出:log4j,通过LogManager的static语句块,加载配置log4j.properties,由OptionConverter去加载log4j.properties,并委托给PropertyConfigurator,去配置RootLogger,根据RootLogger获取Appender,然后根据属性文件初始化Appender,并添加到RootLogger的appender集合中。
Java transient关键字使用小记:http://www.cnblogs.com/lanxuezaipiao/p/3369962.html
Log4j初始化详解:http://donald-draper.iteye.com/blog/2332385
Log4j日志输出详解 :http://donald-draper.iteye.com/blog/2332395
slf4j + Log4j的使用:http://donald-draper.iteye.com/blog/2332407
上一篇简单学习了Log4j的使用,今天来看一下,日志初始化,
我们就从下面这一句来看:
private static Logger log = Logger.getLogger(testLog4j.class);
查看Logger
public class Logger extends Category { protected Logger(String name) { super(name); } //获取Logger public static Logger getLogger(String name) { return LogManager.getLogger(name); } public static Logger getLogger(Class clazz) { return LogManager.getLogger(clazz.getName()); } static { FQCN = (org.apache.log4j.Logger.class).getName(); } }
来看LogManager的getLogger方法
//LogManager
public class LogManager { public static Logger getLogger(String name) { return getLoggerRepository().getLogger(name); } //获取本机LoggerRepository public static LoggerRepository getLoggerRepository() { if(repositorySelector == null) { repositorySelector = new DefaultRepositorySelector(new NOPLoggerRepository()); guard = null; Exception ex = new IllegalStateException("Class invariant violation"); String msg = "log4j called after unloading, see http://logging.apache.org/log4j/1.2/faq.html#unload."; if(isLikelySafeScenario(ex)) LogLog.debug(msg, ex); else LogLog.error(msg, ex); } return repositorySelector.getLoggerRepository(); } public static final String DEFAULT_CONFIGURATION_FILE = "log4j.properties"; static final String DEFAULT_XML_CONFIGURATION_FILE = "log4j.xml"; public static final String DEFAULT_CONFIGURATION_KEY = "log4j.configuration"; public static final String CONFIGURATOR_CLASS_KEY = "log4j.configuratorClass"; public static final String DEFAULT_INIT_OVERRIDE_KEY = "log4j.defaultInitOverride"; private static Object guard = null; private static RepositorySelector repositorySelector; //加载log4j配置文件,先加载log4j.xml,如果log4j.xml不存在, //则加载log4j.properties文件 static { Hierarchy h = new Hierarchy(new RootLogger(Level.DEBUG)); repositorySelector = new DefaultRepositorySelector(h); String override = OptionConverter.getSystemProperty("log4j.defaultInitOverride", null); if(override == null || "false".equalsIgnoreCase(override)) { String configurationOptionStr = OptionConverter.getSystemProperty("log4j.configuration", null); String configuratorClassName = OptionConverter.getSystemProperty("log4j.configuratorClass", null); URL url = null; if(configurationOptionStr == null) { url = Loader.getResource("log4j.xml"); if(url == null) url = Loader.getResource("log4j.properties"); } else { try { url = new URL(configurationOptionStr); } catch(MalformedURLException ex) { url = Loader.getResource(configurationOptionStr); } } if(url != null) { LogLog.debug("Using URL [" + url + "] for automatic log4j configuration."); try { OptionConverter.selectAndConfigure(url, configuratorClassName, getLoggerRepository()); } } } } }
//DefaultRepositorySelector public class DefaultRepositorySelector implements RepositorySelector { public DefaultRepositorySelector(LoggerRepository repository) { this.repository = repository; } public LoggerRepository getLoggerRepository() { return repository; } final LoggerRepository repository; }
//NOPLoggerRepository
public final class NOPLoggerRepository implements LoggerRepository { //从这里看,Logger实际上为NOPLogger public Logger getLogger(String name) { return new NOPLogger(this, name); } }
//NOPLogger
public final class NOPLogger extends Logger { public NOPLogger(NOPLoggerRepository repo, String name) { super(name); repository = repo; level = Level.OFF; parent = this; } }
而Logger继承Category
public class Logger extends Category { protected Logger(String name) { super(name); } }
//Category
public class Category implements AppenderAttachable { protected Category(String name) { additive = true; this.name = name; } protected String name; //volatile protected volatile Level level; protected volatile Category parent; private static final String FQCN; protected ResourceBundle resourceBundle; protected LoggerRepository repository; AppenderAttachableImpl aai; protected boolean additive; static { FQCN = (org.apache.log4j.Category.class).getName(); } }
//Level
public class Level extends Priority implements Serializable { protected Level(int level, String levelStr, int syslogEquivalent) { super(level, levelStr, syslogEquivalent); } public static final int TRACE_INT = 5000; public static final Level OFF = new Level(2147483647, "OFF", 0); public static final Level FATAL = new Level(50000, "FATAL", 0); public static final Level ERROR = new Level(40000, "ERROR", 3); public static final Level WARN = new Level(30000, "WARN", 4); public static final Level INFO = new Level(20000, "INFO", 6); public static final Level DEBUG = new Level(10000, "DEBUG", 7); public static final Level TRACE = new Level(5000, "TRACE", 7); public static final Level ALL = new Level(-2147483648, "ALL", 7); static final long serialVersionUID = 3491141966387921974L; }
//Priority
public class Priority { protected Priority() { level = 10000; levelStr = "DEBUG"; syslogEquivalent = 7; } protected Priority(int level, String levelStr, int syslogEquivalent) { this.level = level; this.levelStr = levelStr; this.syslogEquivalent = syslogEquivalent; } //比较日志级别 public boolean isGreaterOrEqual(Priority r) { return level >= r.level; } transient int level; transient String levelStr; transient int syslogEquivalent; public static final int OFF_INT = 2147483647; public static final int FATAL_INT = 50000; public static final int ERROR_INT = 40000; public static final int WARN_INT = 30000; public static final int INFO_INT = 20000; public static final int DEBUG_INT = 10000; public static final int ALL_INT = -2147483648; public static final Priority FATAL = new Level(50000, "FATAL", 0); public static final Priority ERROR = new Level(40000, "ERROR", 3); public static final Priority WARN = new Level(30000, "WARN", 4); public static final Priority INFO = new Level(20000, "INFO", 6); public static final Priority DEBUG = new Level(10000, "DEBUG", 7); }
我们在回到LogManager加载log4j属性文件,关键在这一句
OptionConverter.selectAndConfigure(url, configuratorClassName, getLoggerRepository());
这个LoggerRepository实际为NOPLoggerRepository
public class OptionConverter { public static void selectAndConfigure(URL url, String clazz, LoggerRepository hierarchy) { Configurator configurator = null; String filename = url.getFile(); if(clazz == null && filename != null && filename.endsWith(".xml")) clazz = "org.apache.log4j.xml.DOMConfigurator"; //XML配置解析 if(clazz != null) { LogLog.debug("Preferred configurator class: " + clazz); configurator = (Configurator)instantiateByClassName(clazz, org.apache.log4j.spi.Configurator.class, null); } else { //java属性文件解析log4j.properties configurator = new PropertyConfigurator(); } //配置NOPLoggerRepository configurator.doConfigure(url, hierarchy); } static String DELIM_START = "${"; static char DELIM_STOP = '}'; static int DELIM_START_LEN = 2; static int DELIM_STOP_LEN = 1; } }
来看log4j.properties属性文件解析
//PropertyConfigurator
public class PropertyConfigurator implements Configurator { protected Hashtable registry; private LoggerRepository repository; protected LoggerFactory loggerFactory; static final String CATEGORY_PREFIX = "log4j.category."; static final String LOGGER_PREFIX = "log4j.logger."; static final String FACTORY_PREFIX = "log4j.factory"; static final String ADDITIVITY_PREFIX = "log4j.additivity."; static final String ROOT_CATEGORY_PREFIX = "log4j.rootCategory"; static final String ROOT_LOGGER_PREFIX = "log4j.rootLogger"; static final String APPENDER_PREFIX = "log4j.appender."; static final String RENDERER_PREFIX = "log4j.renderer."; static final String THRESHOLD_PREFIX = "log4j.threshold"; private static final String THROWABLE_RENDERER_PREFIX = "log4j.throwableRenderer"; private static final String LOGGER_REF = "logger-ref"; private static final String ROOT_REF = "root-ref"; private static final String APPENDER_REF_TAG = "appender-ref"; public static final String LOGGER_FACTORY_KEY = "log4j.loggerFactory"; private static final String RESET_KEY = "log4j.reset"; private static final String INTERNAL_ROOT_NAME = "root"; public PropertyConfigurator() { registry = new Hashtable(11); loggerFactory = new DefaultCategoryFactory(); } //加载URL文件到Properties public void doConfigure(URL configURL, LoggerRepository hierarchy) { Properties props; InputStream istream; props = new Properties(); istream = null; URLConnection uConn = null; URLConnection uConn = configURL.openConnection(); uConn.setUseCaches(false); istream = uConn.getInputStream(); props.load(istream); //加载URL文件到Properties doConfigure(props, hierarchy); } //根据properties文件配置NOPLoggerRepository public void doConfigure(Properties properties, LoggerRepository hierarchy) { repository = hierarchy; String value = properties.getProperty("log4j.debug"); if(value == null) { value = properties.getProperty("log4j.configDebug"); if(value != null) LogLog.warn("[log4j.configDebug] is deprecated. Use [log4j.debug] instead."); } if(value != null) LogLog.setInternalDebugging(OptionConverter.toBoolean(value, true)); String reset = properties.getProperty("log4j.reset"); if(reset != null && OptionConverter.toBoolean(reset, false)) hierarchy.resetConfiguration(); String thresholdStr = OptionConverter.findAndSubst("log4j.threshold", properties); if(thresholdStr != null) { hierarchy.setThreshold(OptionConverter.toLevel(thresholdStr, Level.ALL)); LogLog.debug("Hierarchy threshold set to [" + hierarchy.getThreshold() + "]."); } //配置RootCategory,rootLogger,appenders configureRootCategory(properties, hierarchy); configureLoggerFactory(properties); parseCatsAndRenderers(properties, hierarchy); LogLog.debug("Finished configuring."); registry.clear(); } }
//配置RootCategory,rootLogger,appenders
void configureRootCategory(Properties props, LoggerRepository hierarchy) { String effectiveFrefix = "log4j.rootLogger"; String value = OptionConverter.findAndSubst("log4j.rootLogger", props); if(value == null) { LogLog.debug("Could not find root logger information. Is this OK?"); } else { Logger root = hierarchy.getRootLogger(); synchronized(root) { parseCategory(props, root, effectiveFrefix, "root", value); } } }
来看 OptionConverter.findAndSubst
//返回key对应的属性
public static String findAndSubst(String key, Properties props) { String value; value = props.getProperty(key); }
//NOPLoggerRepository,获取rootLogger
public Logger getRootLogger() { return new NOPLogger(this, "root"); }
//PropertyConfigurator
void parseCategory(Properties props, Logger logger, String optionKey, String loggerName, String value) { StringTokenizer st = new StringTokenizer(value, ","); if(!value.startsWith(",") && !value.equals("")) { if(!st.hasMoreTokens()) return; //获取rootLogger,日志级别 String levelStr = st.nextToken(); if("inherited".equalsIgnoreCase(levelStr) || "null".equalsIgnoreCase(levelStr)) { if(loggerName.equals("root")) LogLog.warn("The root logger cannot be set to null."); else logger.setLevel(null); } else { //设置rootLogger,日志级别 logger.setLevel(OptionConverter.toLevel(levelStr, Level.DEBUG)); } LogLog.debug("Category " + loggerName + " set to " + logger.getLevel()); } //移除Appenders logger.removeAllAppenders(); do { if(!st.hasMoreTokens()) break; String appenderName = st.nextToken().trim(); if(appenderName != null && !appenderName.equals(",")) { LogLog.debug("Parsing appender named \"" + appenderName + "\"."); //根据appenderName解析Appender Appender appender = parseAppender(props, appenderName); if(appender != null) //添加appender logger.addAppender(appender); } } while(true); }
//根据appenderName解析Appender
Appender parseAppender(Properties props, String appenderName) { Appender appender = registryGet(appenderName); if(appender != null) { LogLog.debug("Appender \"" + appenderName + "\" was already parsed."); return appender; } //log4j.appender的前缀 String prefix = "log4j.appender." + appenderName; //log4j.appender.appenderName.layout String layoutPrefix = prefix + ".layout"; //加载Appender,Class, //log4j.appender.D = org.apache.log4j.DailyRollingFileAppender appender = (Appender)OptionConverter.instantiateByKey(props, prefix, org.apache.log4j.Appender.class, null); appender.setName(appenderName); if(appender instanceof OptionHandler) { if(appender.requiresLayout()) { //加载Layout,class, //log4j.appender.D.layout = org.apache.log4j.PatternLayout Layout layout = (Layout)OptionConverter.instantiateByKey(props, layoutPrefix, org.apache.log4j.Layout.class, null); if(layout != null) { appender.setLayout(layout); LogLog.debug("Parsing layout options for \"" + appenderName + "\"."); //设置layout的属性 PropertySetter.setProperties(layout, props, layoutPrefix + "."); LogLog.debug("End of parsing for \"" + appenderName + "\"."); } } String errorHandlerPrefix = prefix + ".errorhandler"; String errorHandlerClass = OptionConverter.findAndSubst(errorHandlerPrefix, props); if(errorHandlerClass != null) { ErrorHandler eh = (ErrorHandler)OptionConverter.instantiateByKey(props, errorHandlerPrefix, org.apache.log4j.spi.ErrorHandler.class, null); if(eh != null) { appender.setErrorHandler(eh); LogLog.debug("Parsing errorhandler options for \"" + appenderName + "\"."); parseErrorHandler(eh, errorHandlerPrefix, props, repository); Properties edited = new Properties(); String keys[] = { errorHandlerPrefix + "." + "root-ref", errorHandlerPrefix + "." + "logger-ref", errorHandlerPrefix + "." + "appender-ref" }; Iterator iter = props.entrySet().iterator(); do { if(!iter.hasNext()) break; java.util.Map.Entry entry = (java.util.Map.Entry)iter.next(); int i; for(i = 0; i < keys.length && !keys[i].equals(entry.getKey()); i++); if(i == keys.length) edited.put(entry.getKey(), entry.getValue()); } while(true); PropertySetter.setProperties(eh, edited, errorHandlerPrefix + "."); LogLog.debug("End of errorhandler parsing for \"" + appenderName + "\"."); } } //设置Appender属性 PropertySetter.setProperties(appender, props, prefix + "."); LogLog.debug("Parsed \"" + appenderName + "\" options."); } parseAppenderFilters(props, appenderName, appender); //将Appender放入registry registryPut(appender); return appender; }
//OptionConverter.instantiateByKey
public static Object instantiateByKey(Properties props, String key, Class superClass, Object defaultValue) { String className = findAndSubst(key, props); if(className == null) { LogLog.error("Could not find value for key " + key); return defaultValue; } else { return instantiateByClassName(className.trim(), superClass, defaultValue); } }
//PropertyConfigurator
// protected Hashtable registry;HashTable<String,Appender>
//将Appender放入registry
void registryPut(Appender appender) { registry.put(appender.getName(), appender); }
下面我们来看看logger.addAppender,都做了些什么
public class Category implements AppenderAttachable { //添加Appender public synchronized void addAppender(Appender newAppender) { if(aai == null) aai = new AppenderAttachableImpl(); aai.addAppender(newAppender); //通知repository,添加Appender事件 repository.fireAddAppenderEvent(this, newAppender); } //移除AllAppenders public synchronized void removeAllAppenders() { if(aai != null) { Vector appenders = new Vector(); for(Enumeration iter = aai.getAllAppenders(); iter != null && iter.hasMoreElements(); appenders.add(iter.nextElement())); aai.removeAllAppenders(); for(Enumeration iter = appenders.elements(); iter.hasMoreElements(); fireRemoveAppenderEvent((Appender)iter.nextElement())); aai = null; } } }
//AppenderAttachableImpl
public class AppenderAttachableImpl implements AppenderAttachable { //添加Appender public void addAppender(Appender newAppender) { if(newAppender == null) return; if(appenderList == null) appenderList = new Vector(1); if(!appenderList.contains(newAppender)) appenderList.addElement(newAppender); } //Vector<Appender> protected Vector appenderList; }
总结:
从以上我们可以看出:log4j,通过LogManager的static语句块,加载配置log4j.properties,由OptionConverter去加载log4j.properties,并委托给PropertyConfigurator,去配置RootLogger,根据RootLogger获取Appender,然后根据属性文件初始化Appender,并添加到RootLogger的appender集合中。
发表评论
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一次服务器事故处理过程及教训
2017-02-24 18:50 1169java虚拟机内存查看相关 ... -
slf4j + Logback使用
2016-10-23 19:44 1381使用logback轻松管理日志: http://blog.cs ... -
slf4j + Logback详解
2016-10-23 19:41 1311Log4j初始化详解:http://donald-draper ... -
slf4j + Log4j 详解
2016-10-23 19:40 1767Log4j初始化详解:http://donald-draper ... -
sfl4j与log4j使用
2016-10-23 11:24 2437slf4j-api、slf4j-log4j12以及log4j之 ... -
Log4j日志输出详解
2016-10-23 00:46 2857Log4j初始化详解:http://donald-draper ... -
log4j的使用
2016-10-22 11:56 630Log4j使用教程:http://www.codeceo.co ... -
Spring集成log4j,日志初始化过程详解
2016-06-22 17:41 7781以前研究过slf4j-log4j的使用,但具体初始化过程不是很 ...
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