自定义logback日志

自定义logback日志组件，自动格式化console日志，并创建 operation_log 与 audit_log文件日志。

源码分析

logger.info(msg) 的执行流程：

1. Logger#buildLoggingEventAndAppend 入口，创建 LoggingEvent 并执行logger对应的 appender
2. Logger#callAppenders 执行本logger与父logger对应的appender
3. AppenderAttachableImpl#appendLoopOnAppenders 执行当前logger的所有appender的doAppend方法
4. UnsynchronizedAppenderBase#append 执行appender类的append 方法输出日志
5. Console的appender执行到 OutputStreamAppender#subAppend
6. LayoutWrappingEncoder#encode开始转成msg
7. PatternLayoutBase#writeLoopOnConverters 一个个的生成pattern对应的字符串
8. OutputStreamAppender#writeBytes 把对应的内容写入 outputStream

因为自定义的字段比如 traceId 需要使用到 MDC, 由MDC写入LoggingEvent#mdcPropertyMap的，且只能设置一次。

public Map<String, String> getMDCPropertyMap() {
    // populate mdcPropertyMap if null
    if (mdcPropertyMap == null) {
        MDCAdapter mdc = MDC.getMDCAdapter();
        if (mdc instanceof LogbackMDCAdapter)
            mdcPropertyMap = ((LogbackMDCAdapter) mdc).getPropertyMap();
        else
            mdcPropertyMap = mdc.getCopyOfContextMap();
    }
    // mdcPropertyMap still null, use emptyMap()
    if (mdcPropertyMap == null)
        mdcPropertyMap = Collections.emptyMap();

    return mdcPropertyMap;
}

public void setMDCPropertyMap(Map<String, String> map) {
    if (mdcPropertyMap != null) {
        throw new IllegalStateException("The MDCPropertyMap has been already set for this event.");
    }
    this.mdcPropertyMap = map;

}

所以如果想通过自定义appender 注入mdc内容一定要保证此 appender 优先级放在第一位。

具体实现

1. 自定义 ConsoleAppender 替换ROOT logger 的ConsoleAppender，并放在执行顺序的第一位
2. 创建 RollingFileAppender 并加入到 ROOT logger 中

ConsoleAppender

需要放在执行位置的第一位，并删除掉应用其他的console日志。

• 通过LoggerFactory.getILoggerFactory()获取到 LoggerContext
• loggerContext.getLogger 获取到ROOT logger
• root.iteratorForAppenders()迭代所有的appender
• root.detachAppender(appender); 删除appender
• root.addAppender(appender); 增加appender

具体实现如下

private void injectRootAppender() {
    LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
    ch.qos.logback.classic.Logger root = loggerContext.getLogger(ch.qos.logback.classic.Logger.ROOT_LOGGER_NAME);
    // 首先移除所有已存在的 ConsoleAppender
    List<Appender<ILoggingEvent>> appenders = new ArrayList<>();
    // 控制台放第一个
    appenders.add(createStdConsoleAppender());
    Iterator<Appender<ILoggingEvent>> appenderIterator = root.iteratorForAppenders();
    while (appenderIterator.hasNext()) {
        Appender<ILoggingEvent> appender = appenderIterator.next();
        root.detachAppender(appender);
        if (appender instanceof ConsoleAppender) {
            continue;
        }
        appenders.add(appender);
    }
    for (Appender<ILoggingEvent> appender : appenders) {
        root.addAppender(appender);
    }
}

private ConsoleAppender<ILoggingEvent> createStdConsoleAppender() {
    LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
    CustomizedConsoleAppender appender = new CustomizedConsoleAppender();
    appender.setContext(loggerContext);
    appender.setName("CONSOLE");
    // 设置输出格式
    PatternLayoutEncoder encoder = new PatternLayoutEncoder();
    encoder.setContext(loggerContext);
    encoder.setPattern("[%d{yyyy-MM-dd HH:mm:ss.SSS}] [%X{traceId}] [%level] [%C#%M] [%thread] %msg%n");
    encoder.start();
    appender.setEncoder(encoder);
    ThresholdFilter filter = new ThresholdFilter();
    filter.setLevel("INFO");
    filter.start();
    appender.addFilter(filter);
    // 启动并添加到 root logger
    appender.start();
    return appender;
}

然后重写 CustomizedConsoleAppender 的 append 方法

public class CustomizedConsoleAppender<E> extends ConsoleAppender<E> {
    @Override
    protected void append(E eventObject) {
        MDC.put("traceId", "X123456789X");
        super.append(eventObject);
        MDC.remove("traceId");
    }
}

RollingFileAppender

loggerContext.getLogger("OperationLogger"); 会自动创建对应的logger
根据这种特性，直接通过以上方式创建logger后增加RollingFileAppender即可。

代码实现：

private void createOperationLogger() {
    // 创建OperationLogger
    LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
    RollingFileAppender<ILoggingEvent> rollingFileAppender = new RollingFileAppender<>();
    rollingFileAppender.setContext(loggerContext);
    rollingFileAppender.setName("OperationLoggerAppender");
    String filePath = "logs/operation.log";
    rollingFileAppender.setFile(filePath);
    PatternLayoutEncoder encoder = new PatternLayoutEncoder();
    encoder.setContext(loggerContext);
    encoder.setPattern("%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n");
    encoder.start();
    rollingFileAppender.setEncoder(encoder);

    SizeAndTimeBasedRollingPolicy<ILoggingEvent> rollingPolicy = new SizeAndTimeBasedRollingPolicy<>();
    rollingPolicy.setContext(loggerContext);
    rollingPolicy.setFileNamePattern("logs/operation_%d{yyyy-MM-dd}_%i.log.gz");
    rollingPolicy.setMaxFileSize(FileSize.valueOf("100mb"));
    rollingPolicy.setMaxHistory(1);
    rollingPolicy.setTotalSizeCap(FileSize.valueOf("500mb"));
    rollingPolicy.setParent(rollingFileAppender);
    rollingPolicy.start();
    // 设置滚动策略
    rollingFileAppender.setRollingPolicy(rollingPolicy);
    // 启动 appender
    rollingFileAppender.start();
    ch.qos.logback.classic.Logger operationLogger = loggerContext.getLogger("OperationLogger");
    operationLogger.addAppender(rollingFileAppender);
    operationLogger.setLevel(ch.qos.logback.classic.Level.INFO);
    operationLogger.setAdditive(false); // 防止日志消息传递到父 logger
}

其他注意点

需要注意的是，为了避免日志的丢失，应该尽早的执行以上的操作。logback的日志初始化是在 LoggingApplicationListener 中实现的。
所以可以自定义 CustomerLogAppliactionListener 来监听 ApplicationPreparedEvent 事件来执行以上操作，注意 order 设置

@Override
public int getOrder() {
    return LoggingApplicationListener.DEFAULT_ORDER + 1;
}