序

本文主要研究一下logback的isDebugEnabled

isDebugEnabled

public final class Loggerimplements org.slf4j.Logger, LocationAwareLogger, LoggingEventAware, AppenderAttachable<ILoggingEvent>, Serializable {//......public boolean isDebugEnabled() {return isDebugEnabled(null);}public boolean isDebugEnabled(Marker marker) {final FilterReply decision = callTurboFilters(marker, Level.DEBUG);if (decision == FilterReply.NEUTRAL) {return effectiveLevelInt <= Level.DEBUG_INT;} else if (decision == FilterReply.DENY) {return false;} else if (decision == FilterReply.ACCEPT) {return true;} else {throw new IllegalStateException("Unknown FilterReply value: " + decision);}}        }        

isDebugEnabled先通过callTurboFilters获取debug级别的FilterReply，若为DENY返回false，若为ACCEPT返回true，若为NEUTRAL则判断effectiveLevelInt是否小于等于DEBUG_INT

callTurboFilters

    /*** Method that calls the attached TurboFilter objects based on the logger and* the level.* * It is used by isYYYEnabled() methods.* * It returns the typical FilterReply values: ACCEPT, NEUTRAL or DENY.* * @param level* @return the reply given by the TurboFilters*/private FilterReply callTurboFilters(Marker marker, Level level) {return loggerContext.getTurboFilterChainDecision_0_3OrMore(marker, this, level, null, null, null);}

callTurboFilters从loggerContext获取getTurboFilterChainDecision_0_3OrMore

getTurboFilterChainDecision_0_3OrMore

ch/qos/logback/classic/LoggerContext.java

    final FilterReply getTurboFilterChainDecision_0_3OrMore(final Marker marker, final Logger logger, final Level level,final String format, final Object[] params, final Throwable t) {if (turboFilterList.size() == 0) {return FilterReply.NEUTRAL;}return turboFilterList.getTurboFilterChainDecision(marker, logger, level, format, params, t);}

该方法先判断turboFilterList是否为空，为空则返回NEUTRAL，否则执行turboFilterList.getTurboFilterChainDecision

getTurboFilterChainDecision

ch/qos/logback/classic/spi/TurboFilterList.java

    public FilterReply getTurboFilterChainDecision(final Marker marker, final Logger logger, final Level level,final String format, final Object[] params, final Throwable t) {final int size = size();// if (size == 0) {// return FilterReply.NEUTRAL;// }if (size == 1) {try {TurboFilter tf = get(0);return tf.decide(marker, logger, level, format, params, t);} catch (IndexOutOfBoundsException iobe) {return FilterReply.NEUTRAL;}}Object[] tfa = toArray();final int len = tfa.length;for (int i = 0; i < len; i++) {// for (TurboFilter tf : this) {final TurboFilter tf = (TurboFilter) tfa[i];final FilterReply r = tf.decide(marker, logger, level, format, params, t);if (r == FilterReply.DENY || r == FilterReply.ACCEPT) {return r;}}return FilterReply.NEUTRAL;}

getTurboFilterChainDecision在只有1个TurboFilter的时候执行decide方法，否则遍历TurboFilter，挨个执行decide，一但有DENY或者ACCEPT直接返回，否则最后返回NEUTRAL

小结

logback的isDebugEnabled先通过callTurboFilters获取debug级别的FilterReply，若为DENY返回false，若为ACCEPT返回true，若为NEUTRAL则判断effectiveLevelInt是否小于等于DEBUG_INT。callTurboFilters是一系列isYYYEnabled()共用的，它在turboFilterList是否为空，为空则返回NEUTRAL，在只有1个TurboFilter的时候执行decide方法，否则遍历TurboFilter，挨个执行decide，一但有DENY或者ACCEPT直接返回，否则最后返回NEUTRAL。