聊聊SpringBoot的LogbackLoggingSystem

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本文主要研究一下springboot的LogbackLoggingSystemdlq28资讯网——每日最新资讯28at.com

LoggingSystem

org/springframework/boot/logging/LoggingSystem.javadlq28资讯网——每日最新资讯28at.com

public abstract class LoggingSystem {	public abstract void beforeInitialize();	public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {	}	public void cleanUp() {	}	public Runnable getShutdownHandler() {		return null;	}	public Set<LogLevel> getSupportedLogLevels() {		return EnumSet.allOf(LogLevel.class);	}	public void setLogLevel(String loggerName, LogLevel level) {		throw new UnsupportedOperationException("Unable to set log level");	}	public List<LoggerConfiguration> getLoggerConfigurations() {		throw new UnsupportedOperationException("Unable to get logger configurations");	}	public LoggerConfiguration getLoggerConfiguration(String loggerName) {		throw new UnsupportedOperationException("Unable to get logger configuration");	}				}

LoggingSystem定义了beforeInitialize抽象方法，需要子类实现，，同时还提供了setLogLevel、getLoggerConfigurations、getLoggerConfiguration，默认是抛出UnsupportedOperationExceptiondlq28资讯网——每日最新资讯28at.com

NoOpLoggingSystem

static class NoOpLoggingSystem extends LoggingSystem {		@Override		public void beforeInitialize() {		}		@Override		public void setLogLevel(String loggerName, LogLevel level) {		}		@Override		public List<LoggerConfiguration> getLoggerConfigurations() {			return Collections.emptyList();		}		@Override		public LoggerConfiguration getLoggerConfiguration(String loggerName) {			return null;		}	}

NoOpLoggingSystem继承了LoggingSystem，其方法都是空操作dlq28资讯网——每日最新资讯28at.com

AbstractLoggingSystem

org/springframework/boot/logging/AbstractLoggingSystem.javadlq28资讯网——每日最新资讯28at.com

public abstract class AbstractLoggingSystem extends LoggingSystem {	protected static final Comparator<LoggerConfiguration> CONFIGURATION_COMPARATOR = new LoggerConfigurationComparator(			ROOT_LOGGER_NAME);	private final ClassLoader classLoader;	public AbstractLoggingSystem(ClassLoader classLoader) {		this.classLoader = classLoader;	}	@Override	public void beforeInitialize() {	}	@Override	public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {		if (StringUtils.hasLength(configLocation)) {			initializeWithSpecificConfig(initializationContext, configLocation, logFile);			return;		}		initializeWithConventions(initializationContext, logFile);	}	/**	 * Load sensible defaults for the logging system.	 * @param initializationContext the logging initialization context	 * @param logFile the file to load or {@code null} if no log file is to be written	 */	protected abstract void loadDefaults(LoggingInitializationContext initializationContext, LogFile logFile);	/**	 * Load a specific configuration.	 * @param initializationContext the logging initialization context	 * @param location the location of the configuration to load (never {@code null})	 * @param logFile the file to load or {@code null} if no log file is to be written	 */	protected abstract void loadConfiguration(LoggingInitializationContext initializationContext, String location,			LogFile logFile);	/**	 * Reinitialize the logging system if required. Called when	 * {@link #getSelfInitializationConfig()} is used and the log file hasn't changed. May	 * be used to reload configuration (for example to pick up additional System	 * properties).	 * @param initializationContext the logging initialization context	 */	protected void reinitialize(LoggingInitializationContext initializationContext) {	}	//......}

AbstractLoggingSystem继承了LoggingSystem，它主要是重写了initialize方法，若存在configLocation配置则执行initializeWithSpecificConfig，否则执行initializeWithConventions；它同时还定义了loadDefaults、loadConfiguration抽象方法需要子类实现dlq28资讯网——每日最新资讯28at.com

Slf4JLoggingSystem

org/springframework/boot/logging/Slf4JLoggingSystem.javadlq28资讯网——每日最新资讯28at.com

public abstract class Slf4JLoggingSystem extends AbstractLoggingSystem {	private static final String BRIDGE_HANDLER = "org.slf4j.bridge.SLF4JBridgeHandler";	public Slf4JLoggingSystem(ClassLoader classLoader) {		super(classLoader);	}	@Override	public void beforeInitialize() {		super.beforeInitialize();		configureJdkLoggingBridgeHandler();	}	@Override	public void cleanUp() {		if (isBridgeHandlerAvailable()) {			removeJdkLoggingBridgeHandler();		}	}	@Override	protected void loadConfiguration(LoggingInitializationContext initializationContext, String location,			LogFile logFile) {		Assert.notNull(location, "Location must not be null");		if (initializationContext != null) {			applySystemProperties(initializationContext.getEnvironment(), logFile);		}	}	//......}

Slf4JLoggingSystem继承了AbstractLoggingSystem，它覆盖了beforeInitialize，新增configureJdkLoggingBridgeHandler；其cleanUp方法在isBridgeHandlerAvailable的时候执行removeJdkLoggingBridgeHandler；其loadConfiguration在initializationContext不为null的时候执行applySystemPropertiesdlq28资讯网——每日最新资讯28at.com

configureJdkLoggingBridgeHandler

private void configureJdkLoggingBridgeHandler() {		try {			if (isBridgeJulIntoSlf4j()) {				removeJdkLoggingBridgeHandler();				SLF4JBridgeHandler.install();			}		}		catch (Throwable ex) {			// Ignore. No java.util.logging bridge is installed.		}	}

configureJdkLoggingBridgeHandler主要是判断是否将JUL绑定到SLF4J，是的话则removeJdkLoggingBridgeHandler，然后执行SLF4JBridgeHandler.install()dlq28资讯网——每日最新资讯28at.com

removeJdkLoggingBridgeHandler

private void removeJdkLoggingBridgeHandler() {		try {			removeDefaultRootHandler();			SLF4JBridgeHandler.uninstall();		}		catch (Throwable ex) {			// Ignore and continue		}	}	private void removeDefaultRootHandler() {		try {			Logger rootLogger = LogManager.getLogManager().getLogger("");			Handler[] handlers = rootLogger.getHandlers();			if (handlers.length == 1 && handlers[0] instanceof ConsoleHandler) {				rootLogger.removeHandler(handlers[0]);			}		}		catch (Throwable ex) {			// Ignore and continue		}	}

removeJdkLoggingBridgeHandler主要是执行removeDefaultRootHandler，以及SLF4JBridgeHandler.uninstall()dlq28资讯网——每日最新资讯28at.com

applySystemProperties

protected final void applySystemProperties(Environment environment, LogFile logFile) {		new LoggingSystemProperties(environment).apply(logFile);	}	public void apply(LogFile logFile) {		PropertyResolver resolver = getPropertyResolver();		setSystemProperty(resolver, EXCEPTION_CONVERSION_WORD, "exception-conversion-word");		setSystemProperty(PID_KEY, new ApplicationPid().toString());		setSystemProperty(resolver, CONSOLE_LOG_PATTERN, "pattern.console");		setSystemProperty(resolver, FILE_LOG_PATTERN, "pattern.file");		setSystemProperty(resolver, FILE_CLEAN_HISTORY_ON_START, "file.clean-history-on-start");		setSystemProperty(resolver, FILE_MAX_HISTORY, "file.max-history");		setSystemProperty(resolver, FILE_MAX_SIZE, "file.max-size");		setSystemProperty(resolver, FILE_TOTAL_SIZE_CAP, "file.total-size-cap");		setSystemProperty(resolver, LOG_LEVEL_PATTERN, "pattern.level");		setSystemProperty(resolver, LOG_DATEFORMAT_PATTERN, "pattern.dateformat");		setSystemProperty(resolver, ROLLING_FILE_NAME_PATTERN, "pattern.rolling-file-name");		if (logFile != null) {			logFile.applyToSystemProperties();		}	}

applySystemProperties通过LoggingSystemProperties设置了系统属性方便后续log配置文件使用dlq28资讯网——每日最新资讯28at.com

LogbackLoggingSystem

org/springframework/boot/logging/logback/LogbackLoggingSystem.javadlq28资讯网——每日最新资讯28at.com

public class LogbackLoggingSystem extends Slf4JLoggingSystem {	private static final String CONFIGURATION_FILE_PROPERTY = "logback.configurationFile";	private static final LogLevels<Level> LEVELS = new LogLevels<>();	static {		LEVELS.map(LogLevel.TRACE, Level.TRACE);		LEVELS.map(LogLevel.TRACE, Level.ALL);		LEVELS.map(LogLevel.DEBUG, Level.DEBUG);		LEVELS.map(LogLevel.INFO, Level.INFO);		LEVELS.map(LogLevel.WARN, Level.WARN);		LEVELS.map(LogLevel.ERROR, Level.ERROR);		LEVELS.map(LogLevel.FATAL, Level.ERROR);		LEVELS.map(LogLevel.OFF, Level.OFF);	}	private static final TurboFilter FILTER = new TurboFilter() {		@Override		public FilterReply decide(Marker marker, ch.qos.logback.classic.Logger logger, Level level, String format,				Object[] params, Throwable t) {			return FilterReply.DENY;		}	};	public LogbackLoggingSystem(ClassLoader classLoader) {		super(classLoader);	}	@Override	protected String[] getStandardConfigLocations() {		return new String[] { "logback-test.groovy", "logback-test.xml", "logback.groovy", "logback.xml" };	}	//......}

LogbackLoggingSystem继承了Slf4JLoggingSystem，其getStandardConfigLocations返回logback-test.groovy, logback-test.xml, logback.groovy, logback.xmldlq28资讯网——每日最新资讯28at.com

beforeInitialize

@Override	public void beforeInitialize() {		LoggerContext loggerContext = getLoggerContext();		if (isAlreadyInitialized(loggerContext)) {			return;		}		super.beforeInitialize();		loggerContext.getTurboFilterList().add(FILTER);	}

beforeInitialize方法主要是添加了TurboFilterdlq28资讯网——每日最新资讯28at.com

initialize

@Override	public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {		LoggerContext loggerContext = getLoggerContext();		if (isAlreadyInitialized(loggerContext)) {			return;		}		super.initialize(initializationContext, configLocation, logFile);		loggerContext.getTurboFilterList().remove(FILTER);		markAsInitialized(loggerContext);		if (StringUtils.hasText(System.getProperty(CONFIGURATION_FILE_PROPERTY))) {			getLogger(LogbackLoggingSystem.class.getName()).warn("Ignoring '" + CONFIGURATION_FILE_PROPERTY					+ "' system property. Please use 'logging.config' instead.");		}	}

initialize方法执行super.initialize(initializationContext, configLocation, logFile)，然后markAsInitialized(loggerContext)dlq28资讯网——每日最新资讯28at.com

loadDefaults

@Override	protected void loadDefaults(LoggingInitializationContext initializationContext, LogFile logFile) {		LoggerContext context = getLoggerContext();		stopAndReset(context);		boolean debug = Boolean.getBoolean("logback.debug");		if (debug) {			StatusListenerConfigHelper.addOnConsoleListenerInstance(context, new OnConsoleStatusListener());		}		LogbackConfigurator configurator = debug ? new DebugLogbackConfigurator(context)				: new LogbackConfigurator(context);		Environment environment = initializationContext.getEnvironment();		context.putProperty(LoggingSystemProperties.LOG_LEVEL_PATTERN,				environment.resolvePlaceholders("${logging.pattern.level:${LOG_LEVEL_PATTERN:%5p}}"));		context.putProperty(LoggingSystemProperties.LOG_DATEFORMAT_PATTERN, environment.resolvePlaceholders(				"${logging.pattern.dateformat:${LOG_DATEFORMAT_PATTERN:yyyy-MM-dd HH:mm:ss.SSS}}"));		context.putProperty(LoggingSystemProperties.ROLLING_FILE_NAME_PATTERN, environment				.resolvePlaceholders("${logging.pattern.rolling-file-name:${LOG_FILE}.%d{yyyy-MM-dd}.%i.gz}"));		new DefaultLogbackConfiguration(initializationContext, logFile).apply(configurator);		context.setPackagingDataEnabled(true);	}

loadDefaults方法通过LOG_LEVEL_PATTERN、LOG_DATEFORMAT_PATTERN、ROLLING_FILE_NAME_PATTERN以及LogbackConfigurator来初始化DefaultLogbackConfigurationdlq28资讯网——每日最新资讯28at.com

loadConfiguration

@Override	protected void loadConfiguration(LoggingInitializationContext initializationContext, String location,			LogFile logFile) {		super.loadConfiguration(initializationContext, location, logFile);		LoggerContext loggerContext = getLoggerContext();		stopAndReset(loggerContext);		try {			configureByResourceUrl(initializationContext, loggerContext, ResourceUtils.getURL(location));		}		catch (Exception ex) {			throw new IllegalStateException("Could not initialize Logback logging from " + location, ex);		}		List<Status> statuses = loggerContext.getStatusManager().getCopyOfStatusList();		StringBuilder errors = new StringBuilder();		for (Status status : statuses) {			if (status.getLevel() == Status.ERROR) {				errors.append((errors.length() > 0) ? String.format("%n") : "");				errors.append(status.toString());			}		}		if (errors.length() > 0) {			throw new IllegalStateException(String.format("Logback configuration error detected: %n%s", errors));		}	}	private void configureByResourceUrl(LoggingInitializationContext initializationContext, LoggerContext loggerContext,			URL url) throws JoranException {		if (url.toString().endsWith("xml")) {			JoranConfigurator configurator = new SpringBootJoranConfigurator(initializationContext);			configurator.setContext(loggerContext);			configurator.doConfigure(url);		}		else {			new ContextInitializer(loggerContext).configureByResource(url);		}	}

loadConfiguration方法主要是执行configureByResourceUrl，该方法通过SpringBootJoranConfigurator或者ContextInitializer的configureByResource进行配置dlq28资讯网——每日最新资讯28at.com

小结

springboot定义了LoggingSystem、AbstractLoggingSystem、Slf4JLoggingSystem，依次继承，而LogbackLoggingSystem则继承Slf4JLoggingSystem，它主要是定义了要加载的默认的配置文件logback-test.groovy, logback-test.xml, logback.groovy, logback.xml，以及loadDefaults方法，通过LOG_LEVEL_PATTERN、LOG_DATEFORMAT_PATTERN、ROLLING_FILE_NAME_PATTERN以及LogbackConfigurator来初始化DefaultLogbackConfiguration。dlq28资讯网——每日最新资讯28at.com

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