Sentinel-Log(JUL)

在sentinel中日志的处理都是通过RecordLog来进行，那么sentinel是如何日志实现呢？

如果业务代码中引入了sentinel-logging的话，那么会具体依赖logback等。如果没有，则使用java自带的日志框架JUL实现。对JUL的了解可以查看文章。

    static {
        try {
            // Load user-defined logger implementation first.
            // 具体可以参考sentinel-logging中的代码
            logger = LoggerSpiProvider.getLogger(LOGGER_NAME);
            if (logger == null) {
                // If no customized loggers are provided, we use the default logger based on JUL.
                logger = new JavaLoggingAdapter(LOGGER_NAME, DEFAULT_LOG_FILENAME);
            }
        } catch (Throwable t) {
            System.err.println("Error: failed to initialize Sentinel RecordLog");
            t.printStackTrace();
        }
    }

接下来具体介绍sentinel是如何实现JUL的。

在logger初始化的时候定义了logHander，具体的handler都是自定义的，主要是输出文件DataFileLogHandler和控制台ConsoleHandler

public class JavaLoggingAdapter extends BaseJulLogger implements Logger {

    private final String loggerName;
    private final String fileNamePattern;

    private final java.util.logging.Logger julLogger;
    private final Handler logHandler;

    public JavaLoggingAdapter(String loggerName, String fileNamePattern) {
        AssertUtil.assertNotBlank(loggerName, "loggerName cannot be blank");
        AssertUtil.assertNotBlank(fileNamePattern, "fileNamePattern cannot be blank");
        this.loggerName = loggerName;
        this.fileNamePattern = fileNamePattern;

        this.julLogger = java.util.logging.Logger.getLogger(loggerName);
        this.logHandler = makeLoggingHandler(fileNamePattern, julLogger);
    }

以及打印格式CspFormatter，并设置默认的日志级别为INFO ，具体读者可以查看源代码makeLoggingHandler，这里就不阐述了  。

当打印Info日志的时候，执行   log(julLogger, logHandler, Level.INFO, msg, e)

protected void log(Logger logger, Handler handler, Level level, String detail, Throwable throwable) {
        if (detail == null) {
            return;
        }
        /**
         * 移除非handler的其他handler，并添加handler
         */
        disableOtherHandlers(logger, handler);
        logger.log(level, detail, throwable);
    }