类图

前面代码看出来最终返回的是LoggerContext这个类实现了LogFactory

成员变量

  //表示根logger
    final Logger root = new Logger("ROOT", (Logger)null, this);
    //标识创建了多少个logger
    private int size;
    //未知
    private int noAppenderWarning = 0;
    //<1>接口的实例能监听 logger context 上发生的事件,比如说日志级别的变化
    private final List<LoggerContextListener> loggerContextListenerList = new ArrayList();
    //logger缓存 get一次会存入缓存同时size++下次直接从缓存拿
    private Map<String, Logger> loggerCache = new ConcurrentHashMap();
    //loggerContextVO对象
    private LoggerContextVO loggerContextRemoteView = new LoggerContextVO(this);
    private final TurboFilterList turboFilterList = new TurboFilterList();
    private boolean packagingDataEnabled = false;
    private int maxCallerDataDepth = 8;
    //记录LoggerContext调用了几次方法
    int resetCount = 0;
    private List<String> frameworkPackages;

<1>配置方式

<?xml version="1.0" encoding="UTF-8" ?>
<configuration debug="true" scan="true" scanPeriod="60 seconds">
 
<contextListener class="com.midea.jr.credit.accounting.utils.LoggerStartupListener" />
</configuration>

LoggerFactory

getILoggerFactory

摘自:《logback源码阅读-集成slf4j初始化过程(一)》

复制代码
public static ILoggerFactory getILoggerFactory() {
/**
     * 0:未初始化
     * 1:准备初始化
     * 2:类没有实现LoggerFactoryBinder 相关方法
     * 3:获取binder成功
     * 4:没有找到相关类 
     */
    static volatile int INITIALIZATION_STATE = 0;
    //这个工厂创建NOPLogger实例 是个空实现 
    static final NOPLoggerFactory NOP_FALLBACK_FACTORY = new NOPLoggerFactory();
    public static ILoggerFactory getILoggerFactory() {
        /**
         * 判断是否初始化
         */
        if (INITIALIZATION_STATE == 0) {
            Class var0 = LoggerFactory.class;
            //加锁并判断 防止初始化后释放锁  等待的进来重复加载
            synchronized(LoggerFactory.class) {
                if (INITIALIZATION_STATE == 0) {
                    //标识正在初始化
                    INITIALIZATION_STATE = 1;
                    //<4>执行初始化化绑定
                    performInitialization();
                }
            }
        }

        switch(INITIALIZATION_STATE) {
            case 1:
                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:
                //<1>可以看到此处是根据StaticLoggerBinder 这是一个slf4j继承点 为logback实现 下面会讲 
                return StaticLoggerBinder.getSingleton().getLoggerFactory();
            case 4:
                return NOP_FALLBACK_FACTORY;
            default:
                throw new IllegalStateException("Unreachable code");
        }
    }
}

StaticLoggerBinder

<1>getLoggerFactory

org.slf4j.impl.StaticLoggerBinder#getILoggerFactory

private LoggerContext defaultLoggerContext = new LoggerContext();
public ILoggerFactory getLoggerFactory() {
        if (!this.initialized) {
            return this.defaultLoggerContext;
        } else if (this.contextSelectorBinder.getContextSelector() == null) {
            throw new IllegalStateException("contextSelector cannot be null. See also http://logback.qos.ch/codes.html#null_CS");
        } else {
            return this.contextSelectorBinder.getContextSelector().getLoggerContext();
        }
    }

LoggerContext

getLogger

ch.qos.logback.classic.LoggerContext#getLogger(java.lang.String)

   public final Logger getLogger(String name) {
        //如果name为空抛出异常 正常不会出现
        if (name == null) {
            throw new IllegalArgumentException("name argument cannot be null");
            //如果传入的是root直接返回root Logger
        } else if ("ROOT".equalsIgnoreCase(name)) {
            return this.root;
        } else {
            int i = 0;
            Logger logger = this.root;
            //从缓存中获取Logger如果没有则
            Logger childLogger = (Logger)this.loggerCache.get(name);
            if (childLogger != null) {
                return childLogger;
            } else {
                int h;
                do {
                    //<1>这里根据,号分割依次连续截取
                    h = LoggerNameUtil.getSeparatorIndexOf(name, i);
                    String childName;
                    if (h == -1) {
                        childName = name;
                    } else {
                        childName = name.substring(0, h);
                    }

                    i = h + 1;
                    synchronized(logger) {
                        //<2>会维护父子关系
                        childLogger = logger.getChildByName(childName);
                        if (childLogger == null) {
                            childLogger = logger.createChildByName(childName);
                            this.loggerCache.put(childName, childLogger);
                            //每次创建count++
                            this.incSize();
                        }
                    }

                    logger = childLogger;
                } while(h != -1);

                return childLogger;
            }
        }
    }

<1>处会依次截取创建logger并放入cache 同时维护父子关系