使用logback,忽然想到这个问题，然后问了几个同事都没研究过，我来看看logback是如何知道的

打断点如下：

stop in com.sql.mysql.sharding.plugin.ExecutorInterceptor.intercept  stop in ch.qos.logback.classic.Logger.callAppenders  stop in ch.qos.logback.core.encoder.LayoutWrappingEncoder.encode

encode的java函数如下：

    public byte[] encode(E event) {         String txt = layout.doLayout(event);         return convertToBytes(txt);     }

那么layout的值是啥呢？

main[1] print layout  layout = "ch.qos.logback.classic.PatternLayout("%level %date , %logger{36} [%file:%line] , Thread-[%thread] - %msg%n")"

就是我们自己定义的格式，好，继续往下走。

碰到了这个函数

​     protected String writeLoopOnConverters(E event) {         StringBuilder strBuilder = new StringBuilder(INTIAL_STRING_BUILDER_SIZE);         Converter<E> c = head;         while (c != null) {             c.write(strBuilder, event);             c = c.getNext();         }         return strBuilder.toString();     } ​

这里看来是做了一个字符串拼接的功能!,继续

========================================================

Step completed: "thread=main", ch.qos.logback.core.pattern.PatternLayoutBase.writeLoopOnConverters(), line=113 bci=11 113            Converter<E> c = head;  main[1] print head  head = "ch.qos.logback.classic.pattern.LevelConverter@cf3a8fb"

其实也就可以猜到，这里是要一个链表的converter,每个converter构造自己的内容

我们来看看logback提供了哪些converter

---

未完待续,好，继续

1）ch.qos.logback.classic.pattern.LevelConverter

@Override     final public void write(StringBuilder buf, E event) {         String s = convert(event);          if (formattingInfo == null) {             buf.append(s);             return;         }          int min = formattingInfo.getMin();         int max = formattingInfo.getMax();          if (s == null) {             if (0 < min)                 SpacePadder.spacePad(buf, min);             return;         }          int len = s.length();          if (len > max) {             if (formattingInfo.isLeftTruncate()) {                 buf.append(s.substring(len - max));             } else {                 buf.append(s.substring(0, max));             }         } else if (len < min) {             if (formattingInfo.isLeftPad()) {                 SpacePadder.leftPad(buf, s, min);             } else {                 SpacePadder.rightPad(buf, s, min);             }         } else {             buf.append(s);         }     }

2）ch.qos.logback.classic.pattern.DateConverter

略

 3）ch.qos.logback.classic.pattern.LoggerConverter

public class LoggerConverter extends NamedConverter {      protected String getFullyQualifiedName(ILoggingEvent event) {         return event.getLoggerName();     } }

这个在event创建时就赋值了,这样就知道是哪个类里面的log打的消息了

4)ch.qos.logback.classic.pattern.FileOfCallerConverter

获取Java文件

    public StackTraceElement[] getCallerData() {         if (callerDataArray == null) {             callerDataArray = CallerData                             .extract(new Throwable(), fqnOfLoggerClass, loggerContext.getMaxCallerDataDepth(), loggerContext.getFrameworkPackages());         }         return callerDataArray;     }

看起来是获得了一个栈，具体是什么呢，进去看

public static StackTraceElement[] extract(Throwable t, String fqnOfInvokingClass, final int maxDepth, List<String> frameworkPackageList) {         if (t == null) {             return null;         }          StackTraceElement[] steArray = t.getStackTrace();         StackTraceElement[] callerDataArray;          int found = LINE_NA;         for (int i = 0; i < steArray.length; i++) {             if (isInFrameworkSpace(steArray[i].getClassName(), fqnOfInvokingClass, frameworkPackageList)) {                 // the caller is assumed to be the next stack frame, hence the +1.                 found = i + 1;             } else {                 if (found != LINE_NA) {                     break;                 }             }         }          // we failed to extract caller data         if (found == LINE_NA) {             return EMPTY_CALLER_DATA_ARRAY;         }          int availableDepth = steArray.length - found;         int desiredDepth = maxDepth < (availableDepth) ? maxDepth : availableDepth;          callerDataArray = new StackTraceElement[desiredDepth];         for (int i = 0; i < desiredDepth; i++) {             callerDataArray[i] = steArray[found + i];         }         return callerDataArray;     }

其实就是利用了一个new Throwable()的t.getStackTrace(); 来获取一个栈，

但是其实有很多个，那么这么识别出来我要到哪一层呢？

[1] ch.qos.logback.classic.spi.CallerData.extract (CallerData.java:63)   [2] ch.qos.logback.classic.spi.LoggingEvent.getCallerData (LoggingEvent.java:258)   [3] ch.qos.logback.classic.pattern.FileOfCallerConverter.convert (FileOfCallerConverter.java:22)   [4] ch.qos.logback.classic.pattern.FileOfCallerConverter.convert (FileOfCallerConverter.java:19)   [5] ch.qos.logback.core.pattern.FormattingConverter.write (FormattingConverter.java:36)   [6] ch.qos.logback.core.pattern.PatternLayoutBase.writeLoopOnConverters (PatternLayoutBase.java:115)   [7] ch.qos.logback.classic.PatternLayout.doLayout (PatternLayout.java:141)   [8] ch.qos.logback.classic.PatternLayout.doLayout (PatternLayout.java:39)   [9] ch.qos.logback.core.encoder.LayoutWrappingEncoder.encode (LayoutWrappingEncoder.java:115)   [10] ch.qos.logback.core.OutputStreamAppender.subAppend (OutputStreamAppender.java:230)   [11] ch.qos.logback.core.OutputStreamAppender.append (OutputStreamAppender.java:102)   [12] ch.qos.logback.core.UnsynchronizedAppenderBase.doAppend (UnsynchronizedAppenderBase.java:84)   [13] ch.qos.logback.core.spi.AppenderAttachableImpl.appendLoopOnAppenders (AppenderAttachableImpl.java:51)   [14] ch.qos.logback.classic.Logger.appendLoopOnAppenders (Logger.java:270)   [15] ch.qos.logback.classic.Logger.callAppenders (Logger.java:257)   [16] ch.qos.logback.classic.Logger.buildLoggingEventAndAppend (Logger.java:421)   [17] ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus (Logger.java:383)   [18] ch.qos.logback.classic.Logger.info (Logger.java:579)   [19] com.sql.mysql.sharding.plugin.ExecutorInterceptor.intercept (ExecutorInterceptor.java:53)   [20] org.apache.ibatis.plugin.Plugin.invoke (Plugin.java:61)   [21] com.sun.proxy.$Proxy3.update (null)   [22] org.apache.ibatis.session.defaults.DefaultSqlSession.update (DefaultSqlSession.java:198)   [23] org.apache.ibatis.session.defaults.DefaultSqlSession.delete (DefaultSqlSession.java:213)   [24] org.apache.ibatis.binding.MapperMethod.execute (MapperMethod.java:67)   [25] org.apache.ibatis.binding.MapperProxy.invoke (MapperProxy.java:59)   [26] com.sun.proxy.$Proxy4.deleteRole (null)   [27] notransaction.ShardingNoTransaction.main (ShardingNoTransaction.java:24)

其实有一行代码

for (int i = 0; i < steArray.length; i++) {             if (isInFrameworkSpace(steArray[i].getClassName(), fqnOfInvokingClass, frameworkPackageList)) {                 // the caller is assumed to be the next stack frame, hence the +1.                 found = i + 1;             } else {                 if (found != LINE_NA) {                     break;                 }             }         }

关键就是这行代码isInFrameworkSpace

static boolean isInFrameworkSpace(String currentClass, String fqnOfInvokingClass, List<String> frameworkPackageList) {         // the check for org.apache.log4j.Category class is intended to support         // log4j-over-slf4j. it solves http://bugzilla.slf4j.org/show_bug.cgi?id=66         if (currentClass.equals(fqnOfInvokingClass) || currentClass.equals(LOG4J_CATEGORY) || currentClass.startsWith(SLF4J_BOUNDARY)                         || isInFrameworkSpaceList(currentClass, frameworkPackageList)) {             return true;         } else {             return false;         }     }

如果是

1）"ch.qos.logback.classic.Logger"

2)"org.apache.log4j.Category"

3)以"org.slf4j.Logger";开头

4)或者以frameworkPackageList里面的值开头的都是日志框架的

直到找到第一个我们业务自己的为止！

然后把调用栈拷贝出来，再执行下面的函数

    public String convert(ILoggingEvent le) {         StackTraceElement[] cda = le.getCallerData();         if (cda != null && cda.length > 0) {             return cda[0].getFileName();         } else {             return CallerData.NA;         }     }

Step completed: "thread=main", ch.qos.logback.core.pattern.FormattingConverter.write(), line=36 bci=5 36            String s = convert(event);  main[1] step >  Step completed: "thread=main", ch.qos.logback.core.pattern.FormattingConverter.write(), line=38 bci=6 38            if (formattingInfo == null) {  main[1] print s  s = "ExecutorInterceptor.java"

这样就获得了文件名

5)ch.qos.logback.classic.pattern.LineOfCallerConverter

这里会复用上一个步骤的结果

Step completed: "thread=main", ch.qos.logback.classic.spi.LoggingEvent.getCallerData(), line=257 bci=0 257            if (callerDataArray == null) {  main[1] print callerDataArray  callerDataArray = instance of java.lang.StackTraceElement[8] (id=2233)

/**  * Logback: the reliable, generic, fast and flexible logging framework.  * Copyright (C) 1999-2015, QOS.ch. All rights reserved.  *  * This program and the accompanying materials are dual-licensed under  * either the terms of the Eclipse Public License v1.0 as published by  * the Eclipse Foundation  *  *   or (per the licensee's choosing)  *  * under the terms of the GNU Lesser General Public License version 2.1  * as published by the Free Software Foundation.  */ package ch.qos.logback.classic.pattern;  import ch.qos.logback.classic.spi.CallerData; import ch.qos.logback.classic.spi.ILoggingEvent;  public class LineOfCallerConverter extends ClassicConverter {      public String convert(ILoggingEvent le) {         StackTraceElement[] cda = le.getCallerData();         if (cda != null && cda.length > 0) {             return Integer.toString(cda[0].getLineNumber());         } else {             return CallerData.NA;         }     }  } 

这样就获得了行号！！！

6) ch.qos.logback.classic.pattern.ThreadConverter

/**  * Logback: the reliable, generic, fast and flexible logging framework.  * Copyright (C) 1999-2015, QOS.ch. All rights reserved.  *  * This program and the accompanying materials are dual-licensed under  * either the terms of the Eclipse Public License v1.0 as published by  * the Eclipse Foundation  *  *   or (per the licensee's choosing)  *  * under the terms of the GNU Lesser General Public License version 2.1  * as published by the Free Software Foundation.  */ package ch.qos.logback.classic.pattern;  import ch.qos.logback.classic.spi.ILoggingEvent;  /**  * Return the events thread (usually the current thread).  *   * @author Ceki Gülcü  */ public class ThreadConverter extends ClassicConverter {      public String convert(ILoggingEvent event) {         return event.getThreadName();     }  } 

线程名

    public String getThreadName() {         if (threadName == null) {             threadName = (Thread.currentThread()).getName();         }         return threadName;     }

然后还有其它的一些颜色配置，这个看

http://blog.csdn.net/java_zone/article/details/54341029

就好了，需要在真实的shell上才生效，eclipse里的控制台不生效。

好，完毕！