Log4j容器初始化探究(2)

源码:

//利用给定URL配置Logger容器 static public void selectAndConfigure(URL url, String clazz, LoggerRepository hierarchy) { Configurator configurator = null; String filename = url.getFile(); //优先检查使用xml文件,并查看是否有自定义的configurator if(clazz == null && filename != null && filename.endsWith(".xml")) { clazz = "org.apache.log4j.xml.DOMConfigurator"; } if(clazz != null) { LogLog.debug("Preferred configurator class: " + clazz); configurator = (Configurator) instantiateByClassName(clazz, Configurator.class, null); if(configurator == null) { LogLog.error("Could not instantiate configurator ["+clazz+"]."); return; } } else { configurator = new PropertyConfigurator(); } configurator.doConfigure(url, hierarchy); }

源码流程解析:

1.如果没有自定义配置类Configurator并且文件的后缀名是xml.配置类设置为org.apache.log4j.xml.DOMConfigurator

2.如果自定义了配置类,根据配置类的全限定名,发射得到配置类实例

3.上面两种情况都没有匹配成功,默认是PropertyConfigurator配置类

4.调用configurator.doConfigure(url,hierarchy),根据配置文件URL,配置logger容器Hierarchy(已经静态化构造了简单的容器,RootLogger是根节点)

1.3 Configurator探究(以ProptertyConfigurator为例)

Configurator读取配置文件内容,配置Logger容器

1.3.1 doConfigure(URL,LoggerRepository)

源码:

//从URL中读取配置文件,配置Logger容器Hierarchy publicvoid doConfigure(java.net.URL configURL, LoggerRepository hierarchy) { Properties props = new Properties(); LogLog.debug("Reading configuration from URL " + configURL); InputStream istream = null; URLConnection uConn = null; try { uConn = configURL.openConnection(); uConn.setUseCaches(false); istream = uConn.getInputStream(); props.load(istream); } catch (Exception e) { if (e instanceof InterruptedIOException || e instanceof InterruptedException) { Thread.currentThread().interrupt(); } LogLog.error("Could not read configuration file from URL [" + configURL + "].", e); LogLog.error("Ignoring configuration file [" + configURL +"]."); return; } finally { if (istream != null) { try { istream.close(); } catch(InterruptedIOException ignore) { Thread.currentThread().interrupt(); } catch(IOException ignore) { } catch(RuntimeException ignore) { } } } doConfigure(props, hierarchy); }

源码流程解析:

1.文件URL读取文件内容,赋值给Properties

2.调用doConfigure(properties,hierarchy)配置logger容器

1.3.2 doConfigure(Properties , LoggerRepository)

源码:

publicvoiddoConfigure(Properties properties, LoggerRepository hierarchy) { repository = hierarchy; String value = properties.getProperty(LogLog.DEBUG_KEY); 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)); } // if log4j.reset=true then // reset hierarchy String reset = properties.getProperty(RESET_KEY); if (reset != null && OptionConverter.toBoolean(reset, false)) { hierarchy.resetConfiguration(); } String thresholdStr = OptionConverter.findAndSubst(THRESHOLD_PREFIX, properties); if(thresholdStr != null) { hierarchy.setThreshold(OptionConverter.toLevel(thresholdStr, (Level) Level.ALL)); LogLog.debug("Hierarchy threshold set to ["+hierarchy.getThreshold()+"]."); } configureRootCategory(properties, hierarchy); configureLoggerFactory(properties); parseCatsAndRenderers(properties, hierarchy); LogLog.debug("Finished configuring."); // We don't want to hold references to appenders preventing their // garbage collection. registry.clear(); } voidconfigureRootCategory(Properties props, LoggerRepository hierarchy) { String effectiveFrefix = ROOT_LOGGER_PREFIX; String value = OptionConverter.findAndSubst(ROOT_LOGGER_PREFIX, props); if(value == null) { value = OptionConverter.findAndSubst(ROOT_CATEGORY_PREFIX, props); effectiveFrefix = ROOT_CATEGORY_PREFIX; } 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, INTERNAL_ROOT_NAME, value); } } } protectedvoidconfigureLoggerFactory(Properties props) { String factoryClassName = OptionConverter.findAndSubst(LOGGER_FACTORY_KEY,props); if(factoryClassName != null) { LogLog.debug("Setting category factory to ["+factoryClassName+"]."); loggerFactory = (LoggerFactory)OptionConverter.instantiateByClassName(factoryClassName,LoggerFactory.class,loggerFactory); PropertySetter.setProperties(loggerFactory, props, FACTORY_PREFIX + "."); } } protectedvoidparseCatsAndRenderers(Properties props, LoggerRepository hierarchy) { Enumeration enumeration = props.propertyNames(); while(enumeration.hasMoreElements()) { String key = (String) enumeration.nextElement(); if(key.startsWith(CATEGORY_PREFIX) || key.startsWith(LOGGER_PREFIX)) { String loggerName = null; if(key.startsWith(CATEGORY_PREFIX)) { loggerName = key.substring(CATEGORY_PREFIX.length()); } else if(key.startsWith(LOGGER_PREFIX)) { loggerName = key.substring(LOGGER_PREFIX.length()); } String value = OptionConverter.findAndSubst(key, props); Logger logger = hierarchy.getLogger(loggerName, loggerFactory); synchronized(logger) { parseCategory(props, logger, key, loggerName, value); parseAdditivityForLogger(props, logger, loggerName); } } else if(key.startsWith(RENDERER_PREFIX)) { String renderedClass = key.substring(RENDERER_PREFIX.length()); String renderingClass = OptionConverter.findAndSubst(key, props); if(hierarchy instanceof RendererSupport) { RendererMap.addRenderer((RendererSupport) hierarchy, renderedClass, renderingClass); } } else if (key.equals(THROWABLE_RENDERER_PREFIX)) { if (hierarchy instanceof ThrowableRendererSupport) { ThrowableRenderer tr = (ThrowableRenderer) OptionConverter.instantiateByKey(props, THROWABLE_RENDERER_PREFIX, org.apache.log4j.spi.ThrowableRenderer.class, null); if(tr == null) { LogLog.error( "Could not instantiate throwableRenderer."); } else { PropertySetter setter = new PropertySetter(tr); setter.setProperties(props, THROWABLE_RENDERER_PREFIX + "."); ((ThrowableRendererSupport) hierarchy).setThrowableRenderer(tr); } } } } }

源码流程解析:

1.获取log4j.debug(log4j内部是否debug打印日志),如果为ture打印,false不打印。如果没有设置,尝试读取log4j.configdebug(已经废弃,用logdebug取代)

2.读取log4j.reset,如果设置为true,重置logger容器

3.读取log4j.threshold,设置logger容器总阀值,低于阀值将不打印日志。如果没有配置,默认设置为最低级别Level.ALL

4.调用configureRootCategory\(Properties, LoggerRepository\),配置RootLogger.RootLogger级别不能设置为空或者inherit.解析设置RootLogger的Appenders和Filters.

5.调用configureLoggerFactory(Properties props),配置Logger工厂类LoggerFactory.

6.调用parseCatsAndRenderers(Properties, LoggerRepository),配置Logger以及Renderer

2 Web应用