标签：exti queue creat otl obj cas tps logs hide
slf4j: The Simple Logging Facade for java即 java简单的日志门面。
统一定义了一系列的日志接口，使用户可以使用统一的接口来记录日志。logback,log4j等框架都实现了这些接口，启动时动态地决定真正的日志框架。
本文以slf4j+logback的源码来讲解整个绑定和打印日志的流程。
手动阅读目录如下：
可用的日志框架依赖如下:
1 <dependency> 2 <groupId>org.slf4j</groupId> 3 <artifactId>slf4j-simple</artifactId> 4 <version>1.7.5</version> 5 </dependency> 6 <dependency> 7 <groupId>org.slf4j</groupId> 8 <artifactId>slf4j-log4j12</artifactId> 9 <version>1.7.25</version> 10 </dependency> 11 12 <dependency> 13 <groupId>org.slf4j</groupId> 14 <artifactId>slf4j-jdk14</artifactId> 15 <version>1.7.25</version> 16 </dependency> 17 <dependency> 18 <groupId>ch.qos.logback</groupId> 19 <artifactId>logback-classic</artifactId> 20 <scope>runtime</scope> 21 </dependency>
如何使用slf4j的示例代码如下(配合logback的配置文件):
1 import org.slf4j.Logger; 2 import org.slf4j.LoggerFactory; 3 4 5 public class LoggerTest { 6 7 private static final Logger logger = LoggerFactory.getLogger(LoggerTest.class); 8 9 public static void main(String[] args){ 10 logger.info("hello world！"); 11 } 12 13 }
本文以[示例]logback.xml的配置文件为例：
1 <!-- DEBUG级别日志 appender --> 2 <appender name="DEBUG_LOG" class="ch.qos.logback.core.rolling.RollingFileAppender" additivity="true"> 3 <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> 4 <!-- 按天回滚 daily --> 5 <fileNamePattern>/Users/tanling/saveDir/logs/%d{yyyy-MM-dd}/debug-log1.log</fileNamePattern> 6 <!-- 日志最大的历史 60天 --> 7 <maxHistory>60</maxHistory> 8 </rollingPolicy> 9 <encoder> 10 <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger - %msg%n</pattern> 11 </encoder> 12 </appender> 13 14 15 <appender name="DEBUG_LOG_ASYNC" class= "ch.qos.logback.classic.AsyncAppender"> 16 <!-- 不丢失日志.默认的,如果队列的80%已满,则会丢弃TRACT、DEBUG、INFO级别的日志 --> 17 <discardingThreshold >0</discardingThreshold> 18 <!-- 更改默认的队列的深度,该值会影响性能.默认值为256 --> 19 <queueSize>2048</queueSize> 20 <neverBlock>true</neverBlock> 21 <includeCallerData>true</includeCallerData> 22 <maxFlushTime>3000</maxFlushTime> 23 <!-- 添加附加的appender,最多只能添加一个 --> 24 <appender-ref ref ="DEBUG_LOG"/> 25 </appender> 26 27 <!-- root级别 DEBUG --> 28 <root level="INFO"> 29 <!-- 控制台输出 --> 30 <appender-ref ref="STDOUT" /> 31 <!-- 文件输出 --> 32 <appender-ref ref="DEBUG_LOG" /> 33 </root> 34 35 <logger name="org.foo.demo" additivity="true" > 36 <level value="INFO"/> 37 <appender-ref ref="DEBUG_LOG"/> 38 </logger>
点开LoggerFactory.getLogger的源码：
1 //LoggerFactory 2 public static Logger getLogger(String name) { 3 ILoggerFactory iLoggerFactory = getILoggerFactory(); 4 return iLoggerFactory.getLogger(name); 5 } 6 public static ILoggerFactory getILoggerFactory() { 7 if (INITIALIZATION_STATE == UNINITIALIZED) { 8 INITIALIZATION_STATE = ONGOING_INITIALIZATION; 9 // 初始化 这里是后续分析代码的核心 10 performInitialization(); 11 } 12 switch (INITIALIZATION_STATE) { 13 case SUCCESSFUL_INITIALIZATION: 14 // 初始化成功以后，返回StaticLoggerBinder的单例的loggerfactory 15 return StaticLoggerBinder.getSingleton().getLoggerFactory(); 16 case NOP_FALLBACK_INITIALIZATION: 17 return NOP_FALLBACK_FACTORY; 18 case FAILED_INITIALIZATION: 19 throw new IllegalStateException(UNSUCCESSFUL_INIT_MSG); 20 case ONGOING_INITIALIZATION: 21 // support re-entrant behavior. 22 // See also http://bugzilla.slf4j.org/show_bug.cgi?id=106 23 return TEMP_FACTORY; 24 } 25 throw new IllegalStateException("Unreachable code"); 26 } 27 28 private final static void performInitialization() { 29 // 绑定，这里是绑定真正的日志框架 30 bind(); 31 if (INITIALIZATION_STATE == SUCCESSFUL_INITIALIZATION) { 32 versionSanityCheck(); 33 } 34 } 35 36 // ?? 绑定是重点 37 private final static void bind() { 38 try { 39 // 通过类加载器加载 org/slf4j/impl/StaticLoggerBinder.class 40 Set<URL> staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet(); 41 reportMultipleBindingAmbiguity(staticLoggerBinderPathSet); 42 // the next line does the binding 43 // ?? 解析logback配置文件，获取真正的LoggerFactory 44 StaticLoggerBinder.getSingleton(); 45 INITIALIZATION_STATE = SUCCESSFUL_INITIALIZATION; 46 reportActualBinding(staticLoggerBinderPathSet); 47 fixSubstitutedLoggers(); 48 } catch (NoClassDefFoundError ncde) { 49 // 代码略去 50 } catch (java.lang.NoSuchMethodError nsme) { 51 // 代码略去 52 } 53 }
源码解析:
当运行getILoggerFactory方法的时候，首先会执行初始化获取到真正的LoggerFactory,然后返回。bind是重点。
bind里面做了以下几件事情：
slf4j api旨在一次只与一个基础日志框架绑定。如果类路径上存在多个绑定，则slf4j将发出警告，列出这些绑定的位置。如果类路径上有多个绑定，请选择一个且只能使用一个绑定，并删除其他绑定。即使存在多个绑定，slf4j也会选择一个日志框架实现并与之绑定。https://www.slf4j.org/codes.html#multiple_bindings
下面来介绍StaticLoggerBinder的过程(以logback为例)
1 void init() { 2 try { 3 try { 4 // 通过ContextInitializer来解析logback的配置文件，解析的内容记录到LoggerContext中 5 new ContextInitializer(defaultLoggerContext).autoConfig(); 6 } catch (JoranException je) { 7 Util.report("Failed to auto configure default logger context", je); 8 } 9 // logback-292 10 if (!StatusUtil.contextHasStatusListener(defaultLoggerContext)) { 11 StatusPrinter.printInCaseOfErrorsOrWarnings(defaultLoggerContext); 12 } 13 // 将LoggerContext存储到 contextSelectorBinder.getContextSelector()中 14 contextSelectorBinder.init(defaultLoggerContext, KEY); 15 initialized = true; 16 } catch (Throwable t) { 17 // we should never get here 18 Util.report("Failed to instantiate [" + LoggerContext.class.getName() + "]", t); 19 } 20 } 21 22public ILoggerFactory getLoggerFactory() { 23 if (!initialized) { 24 return defaultLoggerContext; 25 } 26 27 if (contextSelectorBinder.getContextSelector() == null) { 28 throw new IllegalStateException("contextSelector cannot be null. See also " + NULL_CS_URL); 29 } 30 // 这里获取到的LoggerFactroy实际上就是LoggerContext 31 return contextSelectorBinder.getContextSelector().getLoggerContext(); 32 }
代码解析：
上面两个方法，我们结合起来看。
接着来分析是如何解析logback配置文件
1// ContextInitializer 2 public void autoConfig() throws JoranException { 3 StatusListenerConfigHelper.installIfAsked(loggerContext); 4 // 获取到logback的配置文件 5 URL url = findURLOfDefaultConfigurationFile(true); 6 if (url != null) { 7 // 存在配置文件的时候解析 8 configureByResource(url); 9 } else { 10 // 不存在配置文件的时候的处理 11 Configurator c = EnvUtil.loadFromServiceLoader(Configurator.class); 12 if (c != null) { 13 try { 14 c.setContext(loggerContext); 15 c.configure(loggerContext); 16 } catch (Exception e) { 17 throw new LogbackException(String.format("Failed to initialize Configurator: %s using ServiceLoader", c != null ? c.getClass() 18 .getCanonicalName() : "null"), e); 19 } 20 } else { 21 BasicConfigurator basicConfigurator = new BasicConfigurator(); 22 basicConfigurator.setContext(loggerContext); 23 basicConfigurator.configure(loggerContext); 24 } 25 } 26 }
代码解析：
获取logback配置文件，获取到则进行配置文件的解析。获取的顺序是这样的：
1 // ② 2 final public static String GROOVY_AUTOCONFIG_FILE = "logback.groovy"; 3 // ④ 4 final public static String AUTOCONFIG_FILE = "logback.xml"; 5 // ③ 6 final public static String TEST_AUTOCONFIG_FILE = "logback-test.xml"; 7 // ① 8 final public static String CONFIG_FILE_PROPERTY = "logback.configurationFile";
最终落到代码EventPlayer上
1// ContextInitializer 2else if (urlString.endsWith("xml")) { 3 JoranConfigurator configurator = new JoranConfigurator(); 4 configurator.setContext(loggerContext); 5 configurator.doConfigure(url); 6 } 1 public void play(List<SaxEvent> aSaxEventList) { 2 eventList = aSaxEventList; 3 SaxEvent se; 4 for (currentIndex = 0; currentIndex < eventList.size(); currentIndex++) { 5 se = eventList.get(currentIndex); 6 7 if (se instanceof StartEvent) { 8 interpreter.startElement((StartEvent) se); 9 // invoke fireInPlay after startElement processing 10 interpreter.getInterpretationContext().fireInPlay(se); 11 } 12 if (se instanceof BodyEvent) { 13 // invoke fireInPlay before characters processing 14 interpreter.getInterpretationContext().fireInPlay(se); 15 interpreter.characters((BodyEvent) se); 16 } 17 if (se instanceof EndEvent) { 18 // invoke fireInPlay before endElement processing 19 interpreter.getInterpretationContext().fireInPlay(se); 20 interpreter.endElement((EndEvent) se); 21 } 22 23 } 24 }
代码解析:
将logback配置文件中的标签会被解析成List。是如何解析的：
标签以"<"为开头的，会解析成StartEven事件。
标签以"<杠"为开头的，会被解析成EndEvent事件。
在"<"xx>"body"<杠xxx>"标签中的body内容，会被解析成BodyEvent事件。
如图参见debug的结果，每个<的标签都是成对出现的，中间是BodyEvent。
对于不同的标签，均会有StartEvent和EndEvent事件。每个标签都有一个对应的Action，其中有begin和end方法，分别对应上面StartEvent和EndEvent事件的处理。
其中BodyEvent对应于Action中的body方法。
| 标签 | 处理标签的StartEvent和EndEvent的Action |
|---|---|
| appender | AppenderAction |
| root | RootLoggerAction |
| logger | LoggerAction |
| appender-ref | AppenderRefAction |
| 属性标签(比如:rollingPolicy) | NestedComplexPropertyIA |
| 属性标签(比如:fileNamePattern) | NestedBasicPropertyIA |
下面主要来介绍下各标签的处理：
其中以示例logback.xml为例：
红色标的数字代表appender=DEBUG_LOG的执行路径。青色数字顺序代表appender=DEBUG_LOG_ASYNC的执行顺序。黄色的数字代表logger=org.foo.demo的执行顺序。紫色的数字代表root的执行顺序。
核心思想就是利用栈的特性，标签开始的是将对象压入栈，结束的时候将对象从栈中出栈，处理内部的标签时只需要从栈中peek一个对象即是其父对象，处理完了后作为属性设置进去。最终所有key=loggerName,value=logger对象都会缓存到LoggerContext中。
1 public final Logger getLogger(final String name) { 2 3 if (name == null) { 4 throw new IllegalArgumentException("name argument cannot be null"); 5 } 6 7 // if we are asking for the root logger, then let us return it without 8 // wasting time 9 if (Logger.ROOT_LOGGER_NAME.equalsIgnoreCase(name)) { 10 return root; 11 } 12 13 int i = 0; 14 Logger logger = root; 15 16 // check if the desired logger exists, if it does, return it 17 // without further ado. 18 // 最终所有的key=loggerName,value=logger实例都会缓存在LoggerContext中的loggerCache中 19 Logger childLogger = (Logger) loggerCache.get(name); 20 // if we have the child, then let us return it without wasting time 21 if (childLogger != null) { 22 return childLogger; 23 } 24 25 // if the desired logger does not exist, them create all the loggers 26 // in between as well (if they don‘t already exist) 27 String childName; 28 // 获取Logger的逻辑 29 while (true) { 30 int h = LoggerNameUtil.getSeparatorIndexOf(name, i); 31 if (h == -1) { 32 childName = name; 33 } else { 34 childName = name.substring(0, h); 35 } 36 // move i left of the last point 37 i = h + 1; 38 synchronized (logger) { 39 childLogger = logger.getChildByName(childName); 40 if (childLogger == null) { 41 childLogger = logger.createChildByName(childName); 42 loggerCache.put(childName, childLogger); 43 incSize(); 44 } 45 } 46 logger = childLogger; 47 if (h == -1) { 48 return childLogger; 49 } 50 } 51 }
代码解析：
当指定的loggerName中没有点号的时候，从rootLogger中获取childLogger,没有的场合，则新建一个Logger对象，其parentLogger为rootLogger。
指定一个类名的时候，loggerName为该类的全类名。
比如org.foo.demo.LoggerTest,
先查找loggerName=org的logger对象；再查找loggerName=org.foo的logger实例；直至创建loggerName=org.foo.demo.LoggerTest的logger对象。
有的场合直接从logger的chidlist结构中获取，这是在解析LoggerAction的时候缓存起来的。
剧透一下，执行打印的时候，会追溯logger的父logger执行appender。
1 private void buildLoggingEventAndAppend(final String localFQCN, final Marker marker, final Level level, final String msg, final Object[] params, 2 final Throwable t) { 3 // 会将方法的调用参数level 消息 params 异常封装成LoggerEvent 4 LoggingEvent le = new LoggingEvent(localFQCN, this, level, msg, t, params); 5 le.setMarker(marker); 6 callAppenders(le); 7 } 8 9 public void callAppenders(ILoggingEvent event) { 10 int writes = 0; 11 // 这里是上述的剧透内容，会遍历执行logger.parent的appender 12 // additive为配置文件中配置的内容，默认为true，当配置为false的时候，会终止追溯其父logger 13 for (Loogger l = this; l != null; l = l.parent) { 14 writes += l.appendLoopOnAppenders(event); 15 if (!l.additive) { 16 break; 17 } 18 } 19 // No appenders in hierarchy 20 if (writes == 0) { 21 loggerContext.noAppenderDefinedWarning(this); 22 } 23 } 24 // logger的aai是AppenderAttachableImpl对象，其中持有多个Appender的list 25 private int appendLoopOnAppenders(ILoggingEvent event) { 26 if (aai != null) { 27 return aai.appendLoopOnAppenders(event); 28 } else { 29 return 0; 30 } 31 } 32 public int appendLoopOnAppenders(E e) { 33 int size = 0; 34 // 找到logger对应的Appender，执行器logger方法 35 for (Appender<E> appender : appenderList) { 36 appender.doAppend(e); 37 size++; 38 } 39 return size; 40 }
代码解析：
将方法的参数封装成LoggingEvent对象，从指定名称的loggery追溯logger的parentLogger，通过logger中持有的appender来执行。
AppenderAction的end方法中会执行启动：
1 public void end(InterpretationContext ec, String name) { 2 if (inError) { 3 return; 4 } 5 // 这里启动appender 6 if (appender instanceof LifeCycle) { 7 ((LifeCycle) appender).start(); 8 } 9 10 Object o = ec.peekObject(); 11 12 if (o != appender) { 13 addWarn("The object at the of the stack is not the appender named [" + appender.getName() + "] pushed earlier."); 14 } else { 15 ec.popObject(); 16 } 17 }
1 public void start() { 2 // 部分代码略 3 // 进行一堆check，然后appender的文件名创建文件，然后打开文件流，将日志以append的方式追加到文件中 4 currentlyActiveFile = new File(getFile()); 5 addInfo("Active log file name: " + getFile()); 6 super.start(); 7 }
1// AsyncAppenderBase 2 @Override 3 public void start() { 4 if (isStarted()) 5 return; 6 if (appenderCount == 0) { 7 addError("No attached appenders found."); 8 return; 9 } 10 if (queueSize < 1) { 11 addError("Invalid queue size [" + queueSize + "]"); 12 return; 13 } 14 blockingQueue = new ArrayBlockingQueue<E>(queueSize); 15 16 if (discardingThreshold == UNDEFINED) 17 discardingThreshold = queueSize / 5; 18 addInfo("Setting discardingThreshold to " + discardingThreshold); 19 worker.setDaemon(true); 20 worker.setName("AsyncAppender-Worker-" + getName()); 21 // make sure this instance is marked as "started" before staring the worker Thread 22 super.start(); 23 worker.start(); 24 } 25 26 @Override 27 protected void append(E eventObject) { 28 // 当队列空间所剩无几的时候 & 日志级别(INFO,DEBU,TRACE)<=INFO的场合，消息直接丢弃 29 if (isQueueBelowDiscardingThreshold() && isDiscardable(eventObject)) { 30 return; 31 } 32 preprocess(eventObject); 33 put(eventObject); 34 } 35 36 private void put(E eventObject) { 37 if (neverBlock) { 38 blockingQueue.offer(eventObject); 39 } else { 40 try { 41 blockingQueue.put(eventObject); 42 } catch (InterruptedException e) { 43 // Interruption of current thread when in doAppend method should not be consumed 44 // by AsyncAppender 45 Thread.currentThread().interrupt(); 46 } 47 } 48 }
代码解析：
1 class Worker extends Thread { 2 3 public void run() { 4 AsyncAppenderBase<E> parent = AsyncAppenderBase.this; 5 AppenderAttachableImpl<E> aai = parent.aai; 6 7 // loop while the parent is started 8 while (parent.isStarted()) { 9 try { 10 E e = parent.blockingQueue.take(); 11 aai.appendLoopOnAppenders(e); 12 } catch (InterruptedException ie) { 13 break; 14 } 15 } 16 17 addInfo("Worker thread will flush remaining events before exiting. "); 18 19 for (E e : parent.blockingQueue) { 20 aai.appendLoopOnAppenders(e); 21 parent.blockingQueue.remove(e); 22 } 23 24 aai.detachAndStopAllAppenders(); 25 } 26 }
代码解析:
asyncAppender中的aai就是同步的appender，这里只要appender开启中，会从blockingQueue队列中取出LoggingEvent交给普通的appender来执行。
以上。
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标签：exti queue creat otl obj cas tps logs hide
原文地址：https://www.cnblogs.com/mianteno/p/10692445.html
