slf4j源码简析

1 //org.slf4j.LoggerFactory的getLogger(Class)
2 public static Logger getLogger(Class clazz) {
3 //调用了getLogger(String name)
4 Logger logger &＃61; getLogger(clazz.getName());
5 return logger;
6 }

1 //org.slf4j.LoggerFactory的getLogger(String)
2 public static Logger getLogger(String name) {
3 //找到真正的LoggerFactory是关键&＃xff0c;厂商&＃xff08;比如logback&＃xff09;会实现org.slf4j.ILoggerFactory接口
4 ILoggerFactory iLoggerFactory &＃61; getILoggerFactory();
5 return iLoggerFactory.getLogger(name);
6 }

1 //org.slf4j.LoggerFactory的getILoggerFactory
2 public static ILoggerFactory getILoggerFactory() {
3 //双重检查&＃xff0c;检查是否已经绑定了相关实现
4 if (INITIALIZATION_STATE &＃61;&＃61; UNINITIALIZED) {
5 synchronized (LoggerFactory.class) {
6 if (INITIALIZATION_STATE &＃61;&＃61; UNINITIALIZED) {
7 INITIALIZATION_STATE &＃61; ONGOING_INITIALIZATION;
8 //bind
9 performInitialization();
10 }
11 }
12 }
13 switch (INITIALIZATION_STATE) {
14 case SUCCESSFUL_INITIALIZATION:
15 //具体的StaticLoggerBinder需要与具体的厂商适配&＃xff08;StaticLoggerBinder不是接口&＃xff0c;是一个具体的类&＃xff09;&＃xff0c;
16 //StaticLoggerBinder会实现org.slf4j.spi.LoggerFactoryBinder接口&＃xff0c;该接口就提供了getLoggerFactory方法&＃xff0c;
17 //getLoggerFactory会返回org.slf4j.ILoggerFactory&＃xff0c;调用org.slf4j.ILoggerFactory的getLogger就可以得到org.slf4j.Logger。
18 //这里getLoggerFactory得到的LoggerFactory
19 return StaticLoggerBinder.getSingleton().getLoggerFactory();
20 case ......
21 }
22 throw new IllegalStateException("Unreachable code");
23 }

1 //org.slf4j.LoggerFactory的performInitialization的核心逻辑在bind方法
2 private final static void bind() {
3 try {
4 Set staticLoggerBinderPathSet &＃61; null;
5 if (!isAndroid()) {
6 //findPossibleStaticLoggerBinderPathSet会寻找到所有的"org/slf4j/impl/StaticLoggerBinder.class"&＃xff0c;
7 staticLoggerBinderPathSet &＃61; findPossibleStaticLoggerBinderPathSet();
8 //如果找到了多个binder则打印这些候选者
9 reportMultipleBindingAmbiguity(staticLoggerBinderPathSet);
10 }
11 //这里进行了真正的bind&＃xff0c;slf api中并没有StaticLoggerBinder的具体类&＃xff0c;
12 //具体的StaticLoggerBinder需要与具体的厂商适配&＃xff08;logback本身就实现了StaticLoggerBinder&＃xff0c;不需要slf4j适配&＃xff0c;log4j就需要引入slf4j-log4j12依赖来实现适配&＃xff0c;slf4j-log4j12中就有StaticLoggerBinder&＃xff09;&＃xff0c;
13 //StaticLoggerBinder会有一个getSingleton静态方法&＃xff0c;通过该方法得到一个StaticLoggerBinder实例&＃xff08;单例&＃xff09;。
14 //StaticLoggerBinder会实现org.slf4j.spi.LoggerFactoryBinder接口&＃xff0c;该接口提供了getLoggerFactory方法&＃xff0c;
15 //从而可以通过StaticLoggerBinder.getSingleton().getLoggerFactory()得到org.slf4j.ILoggerFactory。
16 //可能会有多个StaticLoggerBinder&＃xff0c;选择哪一个由jvm的类加载决定。
17 StaticLoggerBinder.getSingleton();
18 INITIALIZATION_STATE &＃61; SUCCESSFUL_INITIALIZATION;
19 reportActualBinding(staticLoggerBinderPathSet);
20 fixSubstituteLoggers();
21 replayEvents();
22 // release all resources in SUBST_FACTORY
23 SUBST_FACTORY.clear();
24 } catch (NoClassDefFoundError ncde) {
25 //......
26 }
27 }