怎么在springboot中设置默认日志框架

今天就跟大家聊聊有关怎么在springboot中设置默认日志框架，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。

环境配置：macbook； intellij idea community edition 2020.03 ； gradle 6.8.3 jdk1.8 ；

gradle引用包如下：

dependencies {  compile "com.alibaba:fastjson:1.2.75"  compile "mysql:mysql-connector-java"   //spring  compile("org.springframework.boot:spring-boot-starter")  compile("org.mybatis.spring.boot:mybatis-spring-boot-starter:2.1.4")  compile("org.springframework.boot:spring-boot-starter-web")  compile("org.springframework.boot:spring-boot-starter-actuator")   //lombok  compileOnly 'org.projectlombok:lombok'  annotationProcessor 'org.projectlombok:lombok'   //test  testCompile('org.springframework.boot:spring-boot-starter-test')  testImplementation 'io.projectreactor:reactor-test'}

springboot 默认日志使用的是logback(引入spring-boot-starter包后，就自动引入了logback-core,logback-classic两个包，当然还有slf4j的包)，当springboot启动时，org.springframework.boot.context.logging.LoggingApplicationListener，该类211行注册的监控事件会被ApplicationStartingEvent触发；如下代码所示，会调用onApplicationStartingEvent初始化loggingSystem，而使用哪个日志组件，就要看loggingSystem初始化的值了

@Override  public void onApplicationEvent(ApplicationEvent event) {    if (event instanceof ApplicationStartingEvent) {      onApplicationStartingEvent((ApplicationStartingEvent) event);    }    else if (event instanceof ApplicationEnvironmentPreparedEvent) {      onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);    }    else if (event instanceof ApplicationPreparedEvent) {      onApplicationPreparedEvent((ApplicationPreparedEvent) event);    }    else if (event instanceof ContextClosedEvent        && ((ContextClosedEvent) event).getApplicationContext().getParent() == null) {      onContextClosedEvent();    }    else if (event instanceof ApplicationFailedEvent) {      onApplicationFailedEvent();    }  }   private void onApplicationStartingEvent(ApplicationStartingEvent event) {    this.loggingSystem = LoggingSystem.get(event.getSpringApplication().getClassLoader());    this.loggingSystem.beforeInitialize();  }

如下图是org.springframework.boot.logging.LoggingSystem类里面get函数的内容：首先会从system.getProperty中获取className，新生成的项目，取到的这个值都为空，SYSTEM_PROPERTY是一个固定值，就是该类的名字；那么loggingSystem的值就是从SYSTEM_FACTORY.getLoggingSystem(classLoader);获取到的；接下来我们得看LoggingSystemFactory.fromSpringFactories.getLoggingSystem取的值是什么了；

public static final String SYSTEM_PROPERTY = LoggingSystem.class.getName();private static final LoggingSystemFactory SYSTEM_FACTORY = LoggingSystemFactory.fromSpringFactories();public static LoggingSystem get(ClassLoader classLoader) {    String loggingSystemClassName = System.getProperty(SYSTEM_PROPERTY);    if (StringUtils.hasLength(loggingSystemClassName)) {      if (NONE.equals(loggingSystemClassName)) {        return new NoOpLoggingSystem();      }      return get(classLoader, loggingSystemClassName);    }    LoggingSystem loggingSystem = SYSTEM_FACTORY.getLoggingSystem(classLoader);    Assert.state(loggingSystem != null, "No suitable logging system located");    return loggingSystem;  }   private static LoggingSystem get(ClassLoader classLoader, String loggingSystemClassName) {    try {      Class<?> systemClass = ClassUtils.forName(loggingSystemClassName, classLoader);      Constructor<?> constructor = systemClass.getDeclaredConstructor(ClassLoader.class);      constructor.setAccessible(true);      return (LoggingSystem) constructor.newInstance(classLoader);    }    catch (Exception ex) {      throw new IllegalStateException(ex);    }  }

LoggingSystemFactory是一个接口，它的实现类在spring-boot-start有4个，其中3个是在内部内类实现，DelegatingLoggingSystemFactory（JavaLoggingSystem，Log4J2LoggingSystem，LogbackLoggingSystem，内部类实现）。上面SYSTEM_FACTORY的实现就是DelegatingLoggingSystemFactory这个类，如下代码中delegates的值为JavaLoggingSystem，Log4J2LoggingSystem，LogbackLoggingSystem；三个类具体的加载逻辑在SpringFactoriesLoader.loadFactories函数中，最终返回的loggingSystem就是前面函数返回列表中的第一个；SpringFactoriesLoader.loadFactories 才是决定springboot默认会使用哪个日志组件关键：该类是spring的核心组件类，在spring-core包中，org.springframework.core.io.support.SpringFactoriesLoader；loggingSystem的值=LogbackLoggingSystem

public interface LoggingSystemFactory {     LoggingSystem getLoggingSystem(ClassLoader classLoader);     static LoggingSystemFactory fromSpringFactories() {   return new DelegatingLoggingSystemFactory(      (classLoader) -> SpringFactoriesLoader.loadFactories(LoggingSystemFactory.class, classLoader));  } }class DelegatingLoggingSystemFactory implements LoggingSystemFactory {   private final Function<ClassLoader, List<LoggingSystemFactory>> delegates;     DelegatingLoggingSystemFactory(Function<ClassLoader, List<LoggingSystemFactory>> delegates) {   this.delegates = delegates;  }   @Override  public LoggingSystem getLoggingSystem(ClassLoader classLoader) {   List<LoggingSystemFactory> delegates = (this.delegates != null) ? this.delegates.apply(classLoader) : null;   if (delegates != null) {     for (LoggingSystemFactory delegate : delegates) {      LoggingSystem loggingSystem = delegate.getLoggingSystem(classLoader);      if (loggingSystem != null) {        return loggingSystem;      }     }   }   return null;  } }

看完上述内容，你们对怎么在springboot中设置默认日志框架有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注编程网行业资讯频道，感谢大家的支持。