分析info 日志
SimpleLog初始化
- SimpleLog静态初始化
- SimpleLog 构造初始化
  - 获取属性
- SimpleLog 属性总结
日志打印分析
- 是否启用日志级别 isLevelEnabled
- 打印日志
  - 打印
控制台输出

分析info 日志

public class Main {public static void main(String[] args) {Log logger = LogFactory.getLog(Main.class);//**重点**logger.info("message");}
}

SimpleLog初始化

SimpleLog静态初始化

触发初始化的地方:
//org.apache.commons.logging.impl.LogFactoryImpl::createLogFromClass
c = Class.forName(logAdapterClassName, true, currentCL);

 // Initialize class attributes.// Load properties file, if found.// Override with system properties.static {// Add props from the resource simplelog.properties// 从simplelog.properties 载入属性到 simpleLogProps 中InputStream in = getResourceAsStream("simplelog.properties");if(null != in) {try {simpleLogProps.load(in);in.close();} catch(java.io.IOException e) {// ignored}}// static protected final String systemPrefix = "org.apache.commons.logging.simplelog.";// 是否显示日志：org.apache.commons.logging.simplelog.showlogname,  默认值：falseshowLogName = getBooleanProperty( systemPrefix + "showlogname", showLogName);// org.apache.commons.logging.simplelog.showShortLogname 是否显示短日志名称  默认值：trueshowShortName = getBooleanProperty( systemPrefix + "showShortLogname", showShortName);// org.apache.commons.logging.simplelog.showdatetime 是否显示时间 默认值：false showDateTime = getBooleanProperty( systemPrefix + "showdatetime", showDateTime);if(showDateTime) {//static protected final String DEFAULT_DATE_TIME_FORMAT = "yyyy/MM/dd HH:mm:ss:SSS zzz";//static protected String dateTimeFormat = DEFAULT_DATE_TIME_FORMAT;//org.apache.commons.logging.simplelog.dateTimeFormat 时间格式化， 默认值： yyyy/MM/dd HH:mm:ss:SSS zzzdateTimeFormat = getStringProperty(systemPrefix + "dateTimeFormat",dateTimeFormat);try {dateFormatter = new SimpleDateFormat(dateTimeFormat);} catch(IllegalArgumentException e) {// If the format pattern is invalid - use the default formatdateTimeFormat = DEFAULT_DATE_TIME_FORMAT;dateFormatter = new SimpleDateFormat(dateTimeFormat);}}}

SimpleLog 构造初始化

  public SimpleLog(String name) {logName = name;// Set initial log level// Used to be: set default log level to ERROR// IMHO it should be lower, but at least info ( costin ).//设置默认级别为 info setLevel(SimpleLog.LOG_LEVEL_INFO);
// static protected final String systemPrefix = "org.apache.commons.logging.simplelog.";// Set log level from properties//org.apache.commons.logging.simplelog.log.com.aya.MainString lvl = getStringProperty(systemPrefix + "log." + logName);int i = String.valueOf(name).lastIndexOf(".");// 遍历用户包：找到对应的日志级别//org.apache.commons.logging.simplelog.log.com.aya//org.apache.commons.logging.simplelog.log.comwhile(null == lvl && i > -1) {name = name.substring(0,i);lvl = getStringProperty(systemPrefix + "log." + name);i = String.valueOf(name).lastIndexOf(".");}// org.apache.commons.logging.simplelog.defaultlog 用户配置的默认级别if(null == lvl) {lvl =  getStringProperty(systemPrefix + "defaultlog");}if("all".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_ALL);} else if("trace".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_TRACE);} else if("debug".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_DEBUG);} else if("info".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_INFO);} else if("warn".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_WARN);} else if("error".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_ERROR);} else if("fatal".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_FATAL);} else if("off".equalsIgnoreCase(lvl)) {setLevel(SimpleLog.LOG_LEVEL_OFF);}}

获取属性

从系统环境变量中获取，不为null就返回
从simpleLogProps 中获取（从simplelog.properties 载入的）

   private static String getStringProperty(String name) {String prop = null;try {prop = System.getProperty(name);} catch (SecurityException e) {; // Ignore}return (prop == null) ? simpleLogProps.getProperty(name) : prop;}

SimpleLog 属性总结

复制配置: https://blog.csdn.net/gxmark/article/details/7338253
新建配置文件：simplelog.properties
org.apache.commons.logging.simplelog.defaultlog=trace org.apache.commons.logging.simplelog.log.XXXXXX=debug org.apache.commons.logging.simplelog.showlogname=true org.apache.commons.logging.simplelog.showShortLogname=true org.apache.commons.logging.simplelog.showdatetime=true org.apache.commons.logging.simplelog.dateTimeFormat=yyyy-MM-dd hh:mm:ss

日志打印分析

    public final void info(Object message) {if (isLevelEnabled(SimpleLog.LOG_LEVEL_INFO)) {log(SimpleLog.LOG_LEVEL_INFO,message,null);}}

是否启用日志级别 isLevelEnabled

    /*** Is the given log level currently enabled?** @param logLevel is this level enabled?*/protected boolean isLevelEnabled(int logLevel) {// log level are numerically ordered so can use simple numeric// comparison// 日志级别是否大于等于当前日志级别return (logLevel >= currentLogLevel);}

打印日志

拼接日志内容
- showDateTime（时间）
- type（日志级别）
- showShortName（用户类的简单名称）
- t (异常信息)
打印

 protected void log(int type, Object message, Throwable t) {// Use a string buffer for better performanceStringBuffer buf = new StringBuffer();// Append date-time if so configuredif(showDateTime) {Date now = new Date();String dateText;synchronized(dateFormatter) {dateText = dateFormatter.format(now);}buf.append(dateText);buf.append(" ");}// Append a readable representation of the log levelswitch(type) {case SimpleLog.LOG_LEVEL_TRACE: buf.append("[TRACE] "); break;case SimpleLog.LOG_LEVEL_DEBUG: buf.append("[DEBUG] "); break;case SimpleLog.LOG_LEVEL_INFO:  buf.append("[INFO] ");  break;case SimpleLog.LOG_LEVEL_WARN:  buf.append("[WARN] ");  break;case SimpleLog.LOG_LEVEL_ERROR: buf.append("[ERROR] "); break;case SimpleLog.LOG_LEVEL_FATAL: buf.append("[FATAL] "); break;}// Append the name of the log instance if so configuredif( showShortName) {if( shortLogName==null ) {// Cut all but the last component of the name for both stylesshortLogName = logName.substring(logName.lastIndexOf(".") + 1);shortLogName =shortLogName.substring(shortLogName.lastIndexOf("/") + 1);}buf.append(String.valueOf(shortLogName)).append(" - ");} else if(showLogName) {buf.append(String.valueOf(logName)).append(" - ");}// Append the messagebuf.append(String.valueOf(message));// Append stack trace if not nullif(t != null) {buf.append(" <");buf.append(t.toString());buf.append(">");java.io.StringWriter sw= new java.io.StringWriter(1024);java.io.PrintWriter pw= new java.io.PrintWriter(sw);t.printStackTrace(pw);pw.close();buf.append(sw.toString());}// Print to the appropriate destinationwrite(buf);}

打印

    protected void write(StringBuffer buffer) {// 系统错误输出System.err.println(buffer.toString());}

控制台输出

2018-06-19 04:37:01 [INFO] Main - message

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commons-logging 分析之: org.apache.commons.logging.impl.SimpleLog