我们在使用logback一类的logging system的时候
总是在代码的前面部分放上这段代码private final Logger log = LoggerFactory.getLogger(AdController.class
这段代码调用了org.slf4j.LoggerFactory line:280
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public static Logger getLogger(Class clazz) {
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return getLogger(clazz.getName());
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}
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public static Logger getLogger(String name) {
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ILoggerFactory iLoggerFactory = getILoggerFactory();
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return iLoggerFactory.getLogger(name);
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}
进入 ch.qos.logback.classic.LoggerContext line:105
Logger childLogger = (Logger) loggerCache.get(name);
loggerCache定义处
private Map<String, Logger> loggerCache;
初始化代码
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public LoggerContext() {
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super();
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this.loggerCache = new ConcurrentHashMap <String, Logger>();
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this.loggerContextRemoteView = new LoggerContextVO(this);
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this.root = new Logger(Logger.ROOT_LOGGER_NAME, null, this);
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this.root.setLevel(Level.DEBUG);
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loggerCache.put(Logger.ROOT_LOGGER_NAME, root);
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initEvaluatorMap();
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size = 1;
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this.frameworkPackages = new ArrayList <String>();
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}
可以看到logger里通过name获取logger的实际上是访问了loggerCache这个支持高并发的hashmap.
以下50行代码 做了最重要的工作,请大家仔细阅读,就会明白了.其实很简单.
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public final Logger getLogger(final String name) {
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if (name == null) {
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throw new IllegalArgumentException("name argument cannot be null");
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}
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// if we are asking for the root logger, then let us return it without
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// wasting time
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if (Logger.ROOT_LOGGER_NAME.equalsIgnoreCase(name)) {
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return root;
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}
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int i = 0;
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Logger logger = root;
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// check if the desired logger exists, if it does, return it
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// without further ado.
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Logger childLogger = (Logger) loggerCache.get(name);
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// if we have the child, then let us return it without wasting time
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if (childLogger != null) {
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return childLogger;
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}
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// if the desired logger does not exist, them create all the loggers
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// in between as well (if they don't already exist)
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String childName;
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while (true) {
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int h = LoggerNameUtil.getSeparatorIndexOf(name, i);
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if (h == -1) {
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childName = name;
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} else {
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childName = name.substring(0, h);
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}
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// move i left of the last point
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i = h + 1;
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synchronized (logger) {
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childLogger = logger.getChildByName(childName);
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if (childLogger == null) {
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childLogger = logger.createChildByName(childName);
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loggerCache.put(childName, childLogger);
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incSize();
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}
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}
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logger = childLogger;
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if (h == -1) {
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return childLogger;
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}
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}
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}
比如 我们给的name是com.colamachine.calendar.CalendarService
那么他会第一次会去找com 如果没有com就创建com的logger
再去寻找com.colamachine 同上创建
再去找并创建com.colamachine.calendar
再去找并创建com.colamachine.calendar.CalendarService.
好看完了代码,这只是我一厢情愿的猜测.现在来开始
果然如此
这样的机制 在内存的开销上是否过大
对于只有6个模块的小系统,轻轻松松的mapsize达到了532个