Question

SpringBoot 日志系统

• Author: HuiFer

• 源码阅读仓库: SourceHot-spring-boot

• 包路径: org.springframework.boot.logging

日志级别

• 日志级别: org.springframework.boot.logging.LogLevel

  public enum LogLevel {
      TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF
  }
  

Java 日志实现

• org.springframework.boot.logging.java.JavaLoggingSystem

  

  static {
      // KEY :  springBoot 定义的日志级别, value: jdk 定义的日志级别
      LEVELS.map(LogLevel.TRACE, Level.FINEST);
      LEVELS.map(LogLevel.DEBUG, Level.FINE);
      LEVELS.map(LogLevel.INFO, Level.INFO);
      LEVELS.map(LogLevel.WARN, Level.WARNING);
      LEVELS.map(LogLevel.ERROR, Level.SEVERE);
      LEVELS.map(LogLevel.FATAL, Level.SEVERE);
      LEVELS.map(LogLevel.OFF, Level.OFF);
  }
  

• LEVELS 对象

  protected static class LogLevels<T> {
      /**
       * key ： SpringBoot 中定义的日志级别, value: 其他日志框架的日志级别
       */
      private final Map<LogLevel, T> systemToNative;
      /**
       * key : 其他日志框架的日志级别 , value: springBoot 中定义中定义的日志级别
       */
      private final Map<T, LogLevel> nativeToSystem;
  }
  

LoggingSystem

• 抽象类

• org.springframework.boot.logging.LoggingSystem

• 一个 map 对象: SYSTEMS

  /**
   * key: 第三方日志框架的类 value: springBoot 中的处理类
   */
  private static final Map<String, String> SYSTEMS;
  
  static {
      Map<String, String> systems = new LinkedHashMap<>();
      systems.put("ch.qos.logback.core.Appender", "org.springframework.boot.logging.logback.LogbackLoggingSystem");
      systems.put("org.apache.logging.log4j.core.impl.Log4jContextFactory",
              "org.springframework.boot.logging.log4j2.Log4J2LoggingSystem");
      systems.put("java.util.logging.LogManager", "org.springframework.boot.logging.java.JavaLoggingSystem");
      SYSTEMS = Collections.unmodifiableMap(systems);
  }
  

• 各个抽象方法

  | 方法名称 | 作用 | | ----------------------- | ---------------------------------- | | beforeInitialize | 初始化之前调用，目的是减少日志输出 | | initialize | 初始化日志 | | cleanUp | 清除日志 | | getShutdownHandler | | | getSupportedLogLevels | 获取支持的日志级别 | | setLogLevel | 设置日志级别 | | getLoggerConfigurations | 获取日志配置 |

get

public static LoggingSystem get(ClassLoader classLoader) {
    // 获取系统属性
    String loggingSystem = System.getProperty(SYSTEM_PROPERTY);

    if (StringUtils.hasLength(loggingSystem)) {
        // 是不是NONE
        if (NONE.equals(loggingSystem)) {
            // 空的日志系统
            return new NoOpLoggingSystem();
        }
        return get(classLoader, loggingSystem);
    }
    // 循环所有日志,
    return SYSTEMS.entrySet().stream().filter((entry) -> ClassUtils.isPresent(entry.getKey(), classLoader))
            .map((entry) ->
            // 实例化具体日志
                get(classLoader, entry.getValue())).findFirst()
            .orElseThrow(() -> new IllegalStateException("No suitable logging system located"));
}

• 实例化日志系统

private static LoggingSystem get(ClassLoader classLoader, String loggingSystemClass) {
    try {
        Class<?> systemClass = ClassUtils.forName(loggingSystemClass, classLoader);
        Constructor<?> constructor = systemClass.getDeclaredConstructor(ClassLoader.class);
        constructor.setAccessible(true);
        return (LoggingSystem) constructor.newInstance(classLoader);
    }
    catch (Exception ex) {
        throw new IllegalStateException(ex);
    }
}

• 默认日志: org.springframework.boot.logging.logback.LogbackLoggingSystem

beforeInitialize

• 初始化之前

  

• 链路

  1. org.springframework.boot.context.logging.LoggingApplicationListener#onApplicationEvent
  2. org.springframework.boot.context.logging.LoggingApplicationListener#onApplicationStartingEvent
  3. org.springframework.boot.logging.LoggingSystem#beforeInitialize

• 因为前文中我们已知对象是：org.springframework.boot.logging.logback.LogbackLoggingSystem 直接看这个类的 beforeInitialize 方法

  @Override
  public void beforeInitialize() {
      // 日志上下文
      LoggerContext loggerContext = getLoggerContext();
      // 是否初始化
      if (isAlreadyInitialized(loggerContext)) {
          return;
      }
      // 父类方法
      super.beforeInitialize();
      // 添加过滤器
      loggerContext.getTurboFilterList().add(FILTER);
  }
  

• 初始化之前的的操作完成了初始化方法开始

initialize

• org.springframework.boot.context.logging.LoggingApplicationListener#onApplicationEnvironmentPreparedEvent

  private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
      if (this.loggingSystem == null) {
          this.loggingSystem = LoggingSystem.get(event.getSpringApplication().getClassLoader());
      }
      initialize(event.getEnvironment(), event.getSpringApplication().getClassLoader());
  }
  

• org.springframework.boot.context.logging.LoggingApplicationListener#initializeSystem

  protected void initialize(ConfigurableEnvironment environment, ClassLoader classLoader) {
      new LoggingSystemProperties(environment).apply();
      this.logFile = LogFile.get(environment);
      if (this.logFile != null) {
          this.logFile.applyToSystemProperties();
      }
      this.loggerGroups = new LoggerGroups(DEFAULT_GROUP_LOGGERS);
      // 早期 的日志级别
      initializeEarlyLoggingLevel(environment);
      // 初始化日志系统
      initializeSystem(environment, this.loggingSystem, this.logFile);
      // 初始化日志级别
      initializeFinalLoggingLevels(environment, this.loggingSystem);
      registerShutdownHookIfNecessary(environment, this.loggingSystem);
  }
  

  private void initializeSystem(ConfigurableEnvironment environment, LoggingSystem system, LogFile logFile) {
      LoggingInitializationContext initializationContext = new LoggingInitializationContext(environment);
      String logConfig = environment.getProperty(CONFIG_PROPERTY);
      if (ignoreLogConfig(logConfig)) {
          // 日志系统初始化
          system.initialize(initializationContext, null, logFile);
      }
      else {
          try {
              ResourceUtils.getURL(logConfig).openStream().close();
              system.initialize(initializationContext, logConfig, logFile);
          }
          catch (Exception ex) {
              // NOTE: We can't use the logger here to report the problem
              System.err.println("Logging system failed to initialize using configuration from '" + logConfig + "'");
              ex.printStackTrace(System.err);
              throw new IllegalStateException(ex);
          }
      }
  }
  

• org.springframework.boot.logging.logback.LogbackLoggingSystem#initialize

  @Override
  public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {
      LoggerContext loggerContext = getLoggerContext();
      if (isAlreadyInitialized(loggerContext)) {
          return;
      }
      // 日志初始化
      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.");
      }
  }
  

• org.springframework.boot.logging.AbstractLoggingSystem#initializeWithConventions

  private void initializeWithConventions(LoggingInitializationContext initializationContext, LogFile logFile) {
      String config = getSelfInitializationConfig();
      if (config != null && logFile == null) {
          // self initialization has occurred, reinitialize in case of property changes
          reinitialize(initializationContext);
          return;
      }
      if (config == null) {
          config = getSpringInitializationConfig();
      }
      if (config != null) {
          loadConfiguration(initializationContext, config, logFile);
          return;
      }
      // 加载默认配置
      loadDefaults(initializationContext, logFile);
  }
  

• org.springframework.boot.logging.logback.LogbackLoggingSystem#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);
  }
  

  @Override
  public void initialize(LoggingInitializationContext initializationContext, String configLocation, LogFile logFile) {
      LoggerContext loggerContext = getLoggerContext();
      // 是否加载过
      if (isAlreadyInitialized(loggerContext)) {
          return;
      }
      // 日志初始化
      super.initialize(initializationContext, configLocation, logFile);
      // 删除 FILTER
      loggerContext.getTurboFilterList().remove(FILTER);
      // 初始化标记
      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.");
      }
  }
  

• 标记 markAsInitialized

  private void markAsInitialized(LoggerContext loggerContext) {
      loggerContext.putObject(LoggingSystem.class.getName(), new Object());
  }
  

此时日志初始化完成。

默认配置文件

• getStandardConfigLocations 这个方法定义了默认配置文件有哪些。

  @Override
  protected String[] getStandardConfigLocations() {
      return new String[] { "logback-test.groovy", "logback-test.xml", "logback.groovy", "logback.xml" };
  }
  

• 切回 org.springframework.boot.logging.AbstractLoggingSystem#initializeWithConventions 方法

• 添加依赖

  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-logging</artifactId>
      <version>${revision}</version>
  </dependency>
  

• 添加配置文件

  

  

• 此时配置文件地址出现了

  protected String getSelfInitializationConfig() {
      // 寻找配置文件
      return findConfig(getStandardConfigLocations());
  }
  

  @Override
  protected String[] getStandardConfigLocations() {
      return new String[] { "logback-test.groovy", "logback-test.xml", "logback.groovy", "logback.xml" };
  }
  

  private String findConfig(String[] locations) {
      for (String location : locations) {
          ClassPathResource resource = new ClassPathResource(location, this.classLoader);
          if (resource.exists()) {
              return "classpath:" + location;
          }
      }
      return null;
  }
  

• 此时自定义配置文件如何获取的已经明了。

reinitialize

@Override
protected void reinitialize(LoggingInitializationContext initializationContext) {
    // 日志上下文重新设置
    getLoggerContext().reset();
    getLoggerContext().getStatusManager().clear();
    // 加载配置文件
    loadConfiguration(initializationContext, getSelfInitializationConfig(), null);
}

@Override
protected void loadConfiguration(LoggingInitializationContext initializationContext, String location,
        LogFile logFile) {
    // 父类方法
    super.loadConfiguration(initializationContext, location, logFile);
    // 获取上下文
    LoggerContext loggerContext = getLoggerContext();
    // 停止并且重启
    stopAndReset(loggerContext);
    try {
        // 配置文件加载
        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")) {
        // logback 日志操作
        JoranConfigurator configurator = new SpringBootJoranConfigurator(initializationContext);
        // 设置上下文
        configurator.setContext(loggerContext);
        // 执行配置
        configurator.doConfigure(url);
    }
    else {
        new ContextInitializer(loggerContext).configureByResource(url);
    }
}

执行配置属于 logback 操作源码不在此进行分析。