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

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

阅读量：5974 次

发布时间：2019-06-19

本文共 7497 字，大约阅读时间需要 24 分钟。

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 the

environment contains a {@code logging.config} property it will be used to bootstrap the

logging system, otherwise a default configuration is used. Regardless, logging levels

will be customized if the environment contains {@code logging.level.*} entries and

logging groups can be defined with {@code logging.group}.

Debug and trace logging for Spring, Tomcat, Jetty and Hibernate will be enabled when

the 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 these

properties you can set {@link #setParseArgs(boolean) parseArgs} to {@code false}.

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.

Some system properties may be set as side effects, and these can be useful if the

logging 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
    
     > DEFAULT_GROUP_LOGGERS;    static {        MultiValueMap
     
       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
      
       > LOG_LEVEL_LOGGERS;    static {        MultiValueMap
       
         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


      
     
      org.springframework.boot
       
     
      spring-boot-starter
       
        
          
       
        org.springframework.boot
           
       
        spring-boot-starter-logging
          
        
      
     
      
     
      org.springframework.boot
       
     
      spring-boot-starter-log4j