初五学习记

今天又是值班的一天闲着也是闲着之前LOG4J还没仔细看过今天抽空调一下记录一下学习过程

测试代码如下

首先获取Logger对象后调用info记录日志(这里我设置了等级)

在读取xml配置后进入 logmessage

这里把string打包成message后传入logmessagesafely方法

    private void logMessageSafely(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            this.logMessageTrackRecursion(fqcn, level, marker, message, throwable);        } finally {            ReusableMessageFactory.release(message);        }    }

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }

    private void tryLogMessage(final String fqcn, final StackTraceElement location, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            this.log(level, marker, fqcn, location, message, throwable);        } catch (Exception var8) {            this.handleLogMessageException(var8, fqcn, message);        }    }

这里获取配置中配置的ReliabilityStrategy 并调用其中对应的log方法

其中config是LoggerConfig对象

    @PerformanceSensitive({"allocation"})    public void log(final String loggerName, final String fqcn, final StackTraceElement location, final Marker marker, final Level level, final Message data, final Throwable t) {        List<Property> props = null;        if (!this.propertiesRequireLookup) {            props = this.properties;        } else if (this.properties != null) {            props = new ArrayList(this.properties.size());            LogEvent event = Log4jLogEvent.newBuilder().setMessage(data).setMarker(marker).setLevel(level).setLoggerName(loggerName).setLoggerFqcn(fqcn).setThrown(t).build();            for(int i = 0; i < this.properties.size(); ++i) {                Property prop = (Property)this.properties.get(i);                String value = prop.isValueNeedsLookup() ? this.config.getStrSubstitutor().replace(event, prop.getValue()) : prop.getValue();                ((List)props).add(Property.createProperty(prop.getName(), value));            }        }        LogEvent logEvent = this.logEventFactory instanceof LocationAwareLogEventFactory ? ((LocationAwareLogEventFactory)this.logEventFactory).createEvent(loggerName, marker, fqcn, location, level, data, (List)props, t) : this.logEventFactory.createEvent(loggerName, marker, fqcn, level, data, (List)props, t);        try {            this.log(logEvent, LoggerConfig.LoggerConfigPredicate.ALL);        } finally {            ReusableLogEventFactory.release(logEvent);        }    }

其中逻辑会走到17行这里会调用默认的对应的日志事件createEvent方法处理后打包成一个LogEvent对象

    private Log4jLogEvent(final String loggerName, final Marker marker, final String loggerFQCN, final Level level, final Message message, final Throwable thrown, final ThrowableProxy thrownProxy, final StringMap contextData, final ContextStack contextStack, final long threadId, final String threadName, final int threadPriority, final StackTraceElement source, final long nanoTime) {        this.instant = new MutableInstant();        this.endOfBatch = false;        this.loggerName = loggerName;        this.marker = marker;        this.loggerFqcn = loggerFQCN;        this.level = level == null ? Level.OFF : level;        this.message = message; //payload被打包到这里了        this.thrown = thrown;        this.thrownProxy = thrownProxy;        this.contextData = contextData == null ? ContextDataFactory.createContextData() : contextData;        this.contextStack = (ContextStack)(contextStack == null ? ThreadContext.EMPTY_STACK : contextStack);        this.threadId = threadId;        this.threadName = threadName;        this.threadPriority = threadPriority;        this.source = source;        if (message instanceof LoggerNameAwareMessage) {            ((LoggerNameAwareMessage)message).setLoggerName(loggerName);        }        this.nanoTime = nanoTime;    }

打包完后往下会调用this.log方法并把刚刚返回的logevent对象传进去处理

        try {            this.log(logEvent, LoggerConfig.LoggerConfigPredicate.ALL);        } finally {            ReusableLogEventFactory.release(logEvent);        }

    protected void log(final LogEvent event, final LoggerConfig.LoggerConfigPredicate predicate) {        if (!this.isFiltered(event)) { //没设置过滤器            this.processLogEvent(event, predicate); //跟到这        }    }

    private void processLogEvent(final LogEvent event, final LoggerConfig.LoggerConfigPredicate predicate) {        event.setIncludeLocation(this.isIncludeLocation());        if (predicate.allow(this)) {            this.callAppenders(event); //跟入这里 重点方法        }        this.logParent(event, predicate);    }

通过方法名称可以知道是调用appenders

appenders是控制日志输出的方式,通过设置不同的appenders可以达到不同的输出形式官方提供了以下

1、FileAppender 　　      普通地输出到本地文件2、FlumeAppender　　   将几个不同源的日志汇集、集中到一处。3、JMSQueueAppender & JMSTopicAppender　　与JMS相关的日志输出4、RewriteAppender 　  对日志事件进行掩码或注入信息5、RollingFileAppender 对日志文件进行封存（详细）6、RoutingAppender　  在输出地之间进行筛选路由7、SMTPAppender　　   将LogEvent发送到指定邮件列表8、SocketAppender　　 将LogEvent以普通格式发送到远程主机9、SyslogAppender　　 将LogEvent以RFC 5424格式发送到远程主机10、AsynchAppender 　将一个LogEvent异步地写入多个不同输出地11、ConsoleAppender　将LogEvent输出到命令行12、FailoverAppender　维护一个队列，系统将尝试向队列中的Appender依次输出LogEvent，直到有一个成功为止

我设置的是console

    @PerformanceSensitive({"allocation"})    protected void callAppenders(final LogEvent event) {        AppenderControl[] controls = this.appenders.get();        for(int i = 0; i < controls.length; ++i) {            controls[i].callAppender(event);        }    }

之后就是调用对应的callappender

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }0

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }1

callappender0->trycallappender->this.appender.append(event) //调用consoleappender的append ->tryappend->directEncodeEvent->(this.getLayout().encode)

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }2

在5行有个totext对我们的event进行处理

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }3

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }4

这里会循环调用formatter中对应的converter中format方法来进行处理

默认有11个

当调用到messagepatternconverter的format时

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }5

注意

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }6

在判断存在$的情况下且$后面是{ 会截取字符串然后调用replace方法

replace方法最终调用到substitute

    private void logMessageTrackRecursion(final String fqcn, final Level level, final Marker marker, final Message message, final Throwable throwable) {        try {            incrementRecursionDepth();            this.tryLogMessage(fqcn, this.getLocation(fqcn), level, marker, message, throwable);        } finally {            decrementRecursionDepth();        }    }7