slf4j 如何启动logback,log4j源码分析

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我是靠谱客的博主缥缈蓝天，最近开发中收集的这篇文章主要介绍slf4j 如何启动logback,log4j源码分析，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

历史

知道java 日志框架的，应该知道log4j，logback，slf4j竟然是一个作者写的，我的天。为啥要写三个。。这个可以去看看相关的文章，今天讨论的门面slf4j是如何驱动logback和log4j的。
入口


//一般日志的开启都是在这里开始的。
private static final Logger logger = LoggerFactory.getLogger(EquipmentController.class);
public static Logger getLogger(Class<?> clazz) {
//从getLogger 方法中获取
Logger logger = getLogger(clazz.getName());
if (DETECT_LOGGER_NAME_MISMATCH) {
Class<?> autoComputedCallingClass = Util.getCallingClass();
if (autoComputedCallingClass != null && nonMatchingClasses(clazz, autoComputedCallingClass)) {
Util.report(String.format("Detected logger name mismatch. Given name: "%s"; computed name: "%s".", logger.getName(), autoComputedCallingClass.getName()));
Util.report("See http://www.slf4j.org/codes.html#loggerNameMismatch for an explanation");
}
}
return logger;
}
//一直跟下去，会进行初始化LoggerFactory,这个loggerFactory是不一样的
// 这个地方是 重点了 因为在初始化LoggerFacotry 的时候是需要时间的，在初始化的期间，还有源源不断的log 在打印
//slf4j 是怎么做的呢
public static ILoggerFactory getILoggerFactory() {
//开始的状态是0
然后在将其锁住 只有一个能够进入初始化
if (INITIALIZATION_STATE == 0) {
Class var0 = LoggerFactory.class;
synchronized(LoggerFactory.class) {
//双重判断 进行预防
if (INITIALIZATION_STATE == 0) {
INITIALIZATION_STATE = 1;
performInitialization();
}
}
}
switch(INITIALIZATION_STATE) {
case 1:
// 在初始化的时候 返回一个临时的factory 进行缓存
return SUBST_FACTORY;
case 2:
throw new IllegalStateException("org.slf4j.LoggerFactory in failed state. Original exception was thrown EARLIER. See also http://www.slf4j.org/codes.html#unsuccessfulInit");
case 3:
return StaticLoggerBinder.getSingleton().getLoggerFactory();
case 4:
return NOP_FALLBACK_FACTORY;
default:
throw new IllegalStateException("Unreachable code");
}
}

初始化的时候使用状态这个方式，然后只有一个进入初始化的过程，其他就进入到一个临时的缓存中，等初始化完成之后，再将其输出到正常Factory中。

//再往里面跟 就有一个方法
private static final void bind() {
String msg;
try {
Set<URL> staticLoggerBinderPathSet = null;
if (!isAndroid()) {
staticLoggerBinderPathSet = findPossibleStaticLoggerBinderPathSet();
reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
}
//重点
初始化
StaticLoggerBinder.getSingleton();
INITIALIZATION_STATE = 3;
reportActualBinding(staticLoggerBinderPathSet);
// 将缓存里面的东西进行输出
fixSubstituteLoggers();
replayEvents();
SUBST_FACTORY.clear();
} catch (NoClassDefFoundError var2) {
msg = var2.getMessage();
if (!messageContainsOrgSlf4jImplStaticLoggerBinder(msg)) {
failedBinding(var2);
throw var2;
}
INITIALIZATION_STATE = 4;
Util.report("Failed to load class "org.slf4j.impl.StaticLoggerBinder".");
Util.report("Defaulting to no-operation (NOP) logger implementation");
Util.report("See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.");
} catch (NoSuchMethodError var3) {
msg = var3.getMessage();
if (msg != null && msg.contains("org.slf4j.impl.StaticLoggerBinder.getSingleton()")) {
INITIALIZATION_STATE = 2;
Util.report("slf4j-api 1.6.x (or later) is incompatible with this binding.");
Util.report("Your binding is version 1.5.5 or earlier.");
Util.report("Upgrade your binding to version 1.6.x.");
}
throw var3;
} catch (Exception var4) {
failedBinding(var4);
throw new IllegalStateException("Unexpected initialization failure", var4);
}
}