【Logback】SpringBoot自动配置Logback全解_springboot logback

一、Logback详解

如果对logback不了解，先参照以下三篇了解一下

1. 【Logback】＜configuration＞标签详解
2. 【Logback】＜appender＞标签详解
3. 【Logback】＜logger＞、＜root＞标签详解

二、Spring Boot自动配置

Spring Boot默认是使用Logback的，并且提供了自动配置，以下对Spring Boot中Logback自动配置Starters的使用说明，基于Spring Boot 2.3.12.RELEASE版本

2.1、控制台输出

默认控制台输出 ERROR 、 WARN 和 INFO 级日志，可以配置来调整

1. yml配置文件方式

debug: true
# 或者
# trace: true
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2. 启动参数

通过启动参数 --level如--debug的方式来控制日志级别

java -jar myapp.jar --debug
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源码： org.springframework.boot.context.logging.LoggingApplicationListener#initializeEarlyLoggingLevel

	private LogLevel springBootLogging = null;
	
	private void initializeEarlyLoggingLevel(ConfigurableEnvironment environment) {
		if (this.parseArgs && this.springBootLogging == null) {
			if (isSet(environment, "debug")) {
				this.springBootLogging = LogLevel.DEBUG;
			}
			if (isSet(environment, "trace")) {
				this.springBootLogging = LogLevel.TRACE;
			}
		}
	}
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2.2、配置文件名称

默认加载名为：logback-spring.xml, logback-spring.groovy, logback.xml, or logback.groovy的配置文件

2.3、配置文件加载顺序

Spring的加载顺序：logback.xml --> application.properties --> logback-spring.xml
注意：日志系统是在Spring上下文之前创建的，因此不能使用@PropertySource配置，建议使用 logback-spring.xml
下文会讲到<springProfile>、<springProperty>标签和此有关系

2.4、日志级别设置

语法： logging.level.<logger-name>=<level>

yml配置使用示例：

logging:
  level:
   root: warn  #root设置为warn级别
   org.springframework.web: debug  #name=org.springframework.web的logger设置为debug级别
   org.hibernate: error   #name=org.hibernate的logger设置为debug级别
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2.5、日志分组

可以把<logger>分组，通过组名来统一配置<logger>的设置

2.5.1、properties使用示例

# 将org.apache.catalina、org.apache.coyote、org.apache.tomcat三个logger设为tomcat组
logging.group.tomcat=org.apache.catalina, org.apache.coyote, org.apache.tomcat
# 将tomcat组的日志级别设置为 TRACE
logging.level.tomcat=TRACE

# 将sql组的日志级别设置为 DEBUG
logging.level.sql=DEBUG
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2.5.2、Spring Boot提供的默认分组

2.4、Spring Boot自定义日志配置

默认值定义位置

1. org.springframework.boot.logging.logback.DefaultLogbackConfiguration
2. org\springframework\boot\spring-boot\2.3.12.RELEASE\spring-boot-2.3.12.RELEASE.jar!\org\springframework\boot\logging\logback\base.xml
3. org\springframework\boot\spring-boot\2.3.12.RELEASE\spring-boot-2.3.12.RELEASE.jar!\org\springframework\boot\logging\logback\defaults.xml
4. org\springframework\boot\spring-boot\2.3.12.RELEASE\spring-boot-2.3.12.RELEASE.jar!\org\springframework\boot\logging\logback\console-appender.xml
5. org\springframework\boot\spring-boot\2.3.12.RELEASE\spring-boot-2.3.12.RELEASE.jar!\org\springframework\boot\logging\logback\file-appender.xml

注意：

xml中变量默认值按logback的语法： ${name:-value}
yml或者properties中使用默认值要按spel表达式 ${name:value}，没有-

2.5、Spring Boot扩展xml变量引用标签

源码：org.springframework.boot.logging.logback.SpringBootJoranConfigurator

class SpringBootJoranConfigurator extends JoranConfigurator {

	private LoggingInitializationContext initializationContext;

	SpringBootJoranConfigurator(LoggingInitializationContext initializationContext) {
		this.initializationContext = initializationContext;
	}

	@Override
	public void addInstanceRules(RuleStore rs) {
		super.addInstanceRules(rs);
		Environment environment = this.initializationContext.getEnvironment();
		rs.addRule(new ElementSelector("configuration/springProperty"), new SpringPropertyAction(environment));
		rs.addRule(new ElementSelector("*/springProfile"), new SpringProfileAction(environment));
		rs.addRule(new ElementSelector("*/springProfile/*"), new NOPAction());
	}
}
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2.5.1、Profile-specific Configuration使用示例

就是对spring.profiles.active的支持，支持某些配置在指定配置文件激活时才有效
示例：

<springProfile name="staging">
    <!-- configuration to be enabled when the "staging" profile is active -->
</springProfile>

<springProfile name="dev | staging">
    <!-- configuration to be enabled when the "dev" or "staging" profiles are active -->
</springProfile>

<springProfile name="!production">
    <!-- configuration to be enabled when the "production" profile is not active -->
</springProfile>
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2.5.2、Environment Properties使用示例

支持在logback-spring.xml中通过<springProperty>引用properties或者yml中的环境变量
示例：

<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host"
        defaultValue="localhost"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
    <remoteHost>${fluentHost}</remoteHost>
    ...
</appender>
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2.6、自定义异常日志输出

1、Spring Boot 提供了一个对异常日志转换器WhitespaceThrowableProxyConverter来自定义logback的异常处理，实现异常日志前后添加空行。
2、Seata-server的源码对Spring Boot的WhitespaceThrowableProxyConverter又做了增强，添加了 ==> <==配置

2.6.1、Spring Boot

package org.springframework.boot.logging.logback;

import ch.qos.logback.classic.pattern.ThrowableProxyConverter;
import ch.qos.logback.classic.spi.IThrowableProxy;
import ch.qos.logback.core.CoreConstants;

/**
 * {@link ThrowableProxyConverter} that adds some additional whitespace around the stack
 * trace.
 *
 * @author Phillip Webb
 * @since 1.0.0
 */
public class WhitespaceThrowableProxyConverter extends ThrowableProxyConverter {

	@Override
	protected String throwableProxyToString(IThrowableProxy tp) {
		return CoreConstants.LINE_SEPARATOR + super.throwableProxyToString(tp) + CoreConstants.LINE_SEPARATOR;
	}

}
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2.6.2、seata server

1. 期望自定义格式：

==>

异常信息

<==

2. 代码实现，摘自 seata-server

package com.qbhj.logback.logback;

import ch.qos.logback.classic.pattern.ExtendedThrowableProxyConverter;
import ch.qos.logback.classic.spi.IThrowableProxy;
import ch.qos.logback.core.CoreConstants;

/**
 * 摘自 seata-server
 */
public class ExtendedWhitespaceThrowableProxyConverter extends ExtendedThrowableProxyConverter {

    @Override
    protected String throwableProxyToString(IThrowableProxy tp) {
        return "==>" + CoreConstants.LINE_SEPARATOR + super.throwableProxyToString(tp)
                + "<==" + CoreConstants.LINE_SEPARATOR + CoreConstants.LINE_SEPARATOR;
    }
}
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3. 使用

• xml配置

<!-- The custom conversion rules -->
<conversionRule conversionWord="wEx2" converterClass="com.qbhj.logback.logback.ExtendedWhitespaceThrowableProxyConverter"/>

<!-- 引用，日志格式最后添加了%wEx2 -->
<springProperty name="FILE_LOG_PATTERN" source="logging.pattern.file" 
        defaultValue="%d{yyyy-MM-dd HH:mm:ss.SSS} %5p --- [%30.30t] %-40.40logger{39} : %m%n%wEx2"/>
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• java

    /**
     * 自定义日志格式：异常转换
     */
    @GetMapping("/custom")
    public void customThrowableProxyConverter() {
        RuntimeException runtimeException = new RuntimeException("测试logback 异常！");
        log.error("logback自定义日志格式......", runtimeException);
    }
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4. 效果演示

14:41:29.461  INFO --- [     http-nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 3 ms
14:41:29.477 ERROR --- [     http-nio-8080-exec-1] c.qbhj.logback.controller.LogController  : logback自定义日志格式......
==>
java.lang.RuntimeException: 测试logback 异常！
    at com.qbhj.logback.controller.LogController.customThrowableProxyConverter(LogController.java:46)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

  。。。。。。

    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
<==
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三、参考资料

https://docs.spring.io/spring-boot/docs/2.3.12.RELEASE/reference/html/spring-boot-features.html#boot-features-logging
https://gitee.com/mirrors/Seata/blob/2.x/server/src/main/java/io/seata/server/logging/logback/ExtendedWhitespaceThrowableProxyConverter.java