让你的spring-boot应用日志随心所欲--spring boot日志深入分析

2025-02-24 技术教程

1.spring boot日志概述

spring boot使用Commons Logging作为内部的日志系统，并且给Java Util Logging，Log4J2以及Logback都提供了默认的配置。
如果使用了spring boot的Starters，那么默认会使用Logback用于记录日志。

2.spring boot日志默认配置

我们启动一个空的spring-boot项目看一下控制台的日志

控制台的默认配置

logging.pattern.console=%clr(%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}
其中%clr为配置不同的颜色输出，支持的颜色有以下几种：

blue
cyan
faint
green
magenta
red
yellow
输出顺序分析：

1、日期和时间--精确到毫秒，并按照时间进行简单的排序，格式为：

%clr(%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}}){faint}

2、日志级别--ERROR,WARN,INFO,DEBUG,TRACE

%clr(${LOG_LEVEL_PATTERN:-%5p})

3、进程ID号

%clr(${PID:- })

4、日志内容，用"---"分隔符分开

%clr(---){faint}

5、线程名字--括在方括号中

%clr([%15.15t]){faint}

6、日志的名字--通常对应的是类名

%clr(%-40.40logger{39}){cyan}
注意：Logback没有FATAL级别（映射到ERROR）

不同日志级别对应的颜色如下

3.spring boot日志配置

可以通过application.properties或者application.yml查看所有配置

每个配置后面都有说明，就不一一赘述了。

4.spring boot日志实现原理

点击配置属性，可以进入LoggingApplicationListener这个类，

`/**

An {@link ApplicationListener} that configures the {@link LoggingSystem}. If theenvironment contains a {@code logging.config} property it will be used to bootstrap thelogging system, otherwise a default configuration is used. Regardless, logging levelswill be customized if the environment contains {@code logging.level.*} entries andlogging groups can be defined with {@code logging.group}.<p>Debug and trace logging for Spring, Tomcat, Jetty and Hibernate will be enabled whenthe environment contains {@code debug} or {@code trace} properties that aren't set to{@code "false"} (i.e. if you start your application using{@literal java -jar myapp.jar [--debug | --trace]}). If you prefer to ignore theseproperties you can set {@link #setParseArgs(boolean) parseArgs} to {@code false}.<p>By default, log output is only written to the console. If a log file is required the{@code logging.path} and {@code logging.file} properties can be used.<p>Some system properties may be set as side effects, and these can be useful if thelogging configuration supports placeholders (i.e. log4j or logback):<ul><li>{@code LOG_FILE} is set to the value of path of the log file that should be written(if any).</li><li>{@code PID} is set to the value of the current process ID if it can be determined.</li></ul>@author Dave Syer@author Phillip Webb@author Andy Wilkinson@author Madhura Bhave@since 2.0.0@see LoggingSystem#get(ClassLoader)
*/`

它实现了GenericApplicationListener接口，它默认定义了日志组DEFAULT_GROUP_LOGGERS和日志级别LOG_LEVEL_LOGGERS

private static final Map<String, List<String>> DEFAULT_GROUP_LOGGERS; static { MultiValueMap<String, String> loggers = new LinkedMultiValueMap<>(); loggers.add("web", "org.springframework.core.codec"); loggers.add("web", "org.springframework.http"); loggers.add("web", "org.springframework.web"); loggers.add("web", "org.springframework.boot.actuate.endpoint.web"); loggers.add("web", "org.springframework.boot.web.servlet.ServletContextInitializerBeans"); loggers.add("sql", "org.springframework.jdbc.core"); loggers.add("sql", "org.hibernate.SQL"); DEFAULT_GROUP_LOGGERS = Collections.unmodifiableMap(loggers); } private static final Map<LogLevel, List<String>> LOG_LEVEL_LOGGERS; static { MultiValueMap<LogLevel, String> loggers = new LinkedMultiValueMap<>(); loggers.add(LogLevel.DEBUG, "sql"); loggers.add(LogLevel.DEBUG, "web"); loggers.add(LogLevel.DEBUG, "org.springframework.boot"); loggers.add(LogLevel.TRACE, "org.springframework"); loggers.add(LogLevel.TRACE, "org.apache.tomcat"); loggers.add(LogLevel.TRACE, "org.apache.catalina"); loggers.add(LogLevel.TRACE, "org.eclipse.jetty"); loggers.add(LogLevel.TRACE, "org.hibernate.tool.hbm2ddl"); LOG_LEVEL_LOGGERS = Collections.unmodifiableMap(loggers); }

你也可以自定义logging.level和logging.group,它们都是map结构。LoggingApplicationListener重写了onApplicationEvent方法，实现日志的打印

@Override public void onApplicationEvent(ApplicationEvent event) { if (event instanceof ApplicationStartingEvent) { onApplicationStartingEvent((ApplicationStartingEvent) event); //1 } else if (event instanceof ApplicationEnvironmentPreparedEvent) { onApplicationEnvironmentPreparedEvent( (ApplicationEnvironmentPreparedEvent) event); //2 } else if (event instanceof ApplicationPreparedEvent) { onApplicationPreparedEvent((ApplicationPreparedEvent) event); //3 } else if (event instanceof ContextClosedEvent && ((ContextClosedEvent) event) .getApplicationContext().getParent() == null) { onContextClosedEvent(); //4 } else if (event instanceof ApplicationFailedEvent) { onApplicationFailedEvent(); //5 } }

第一步：根据classloader里加载的依赖决定使用哪个日志系统？

主要实现有JavaLoggingSystem，Log4J2LoggingSystem，LogbackLoggingSystem

private void onApplicationStartingEvent(ApplicationStartingEvent event) { this.loggingSystem = LoggingSystem .get(event.getSpringApplication().getClassLoader()); this.loggingSystem.beforeInitialize(); }

第二步：通过classpath，enviroment等获取参数初始化日志系统

/** * Initialize the logging system according to preferences expressed through the * {@link Environment} and the classpath. * @param environment the environment * @param classLoader the classloader */ protected void initialize(ConfigurableEnvironment environment, ClassLoader classLoader) { new LoggingSystemProperties(environment).apply(); LogFile logFile = LogFile.get(environment); if (logFile != null) { logFile.applyToSystemProperties(); } initializeEarlyLoggingLevel(environment); initializeSystem(environment, this.loggingSystem, logFile); initializeFinalLoggingLevels(environment, this.loggingSystem); registerShutdownHookIfNecessary(environment, this.loggingSystem); }

第三步：注册springBootLoggingSystem

private void onApplicationPreparedEvent(ApplicationPreparedEvent event) { ConfigurableListableBeanFactory beanFactory = event.getApplicationContext() .getBeanFactory(); if (!beanFactory.containsBean(LOGGING_SYSTEM_BEAN_NAME)) { beanFactory.registerSingleton(LOGGING_SYSTEM_BEAN_NAME, this.loggingSystem); } }

第四步和第五步：日志系统清洗

private void onContextClosedEvent() { if (this.loggingSystem != null) { this.loggingSystem.cleanUp(); } } private void onApplicationFailedEvent() { if (this.loggingSystem != null) { this.loggingSystem.cleanUp(); } }

5.自定义配置文件

日志系统自定义配置文件
Logback

logback-spring.xml, logback-spring.groovy, logback.xml, or logback.groovy

Log4j2

log4j2-spring.xml or log4j2.xml

JDK (Java Util Logging)

logging.properties

6.总结

　　spring boot日志系统封装了logback，log4j2和java log，默认情况下使用java log，一旦使用各种starts，则默认使用Log4J2，也可以通过classpath来改变，pom.xml指定

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-logging</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-log4j</artifactId> </dependency>

参考资料

【1】https://docs.spring.io/spring-boot/docs/2.1.2.RELEASE/reference/htmlsingle/#boot-features-logging-format

【2】https://www.jb51.net/article/133795.htm