How Springboot uses Logback to implement log configuration

Overview

By default, SpringBoot internally uses logback as the framework for system log implementation, which outputs logs to the console and does not write them to log files. If configured in application.properties or application.yml, only simple scenarios, saving paths, log formats, etc. can be configured. Complex scenarios (distinguishing between info and error logs, generating a log file every day, etc.) cannot be satisfied, so you can only customize the configuration file logback-spring.xml or logback.xml.

Detailed explanation of logback configuration

First, let’s understand logback.

logback is mainly divided into three modules:

• logback-core: is the basic module of the other two modules

• logback-classic: It is an extension of the core module, equivalent to an improved version of log4j. The classic module implements the Slf4j API, so it can be easily switched with other log frameworks directly.

• logback-access: Integrate with the Servlet container to provide http access log functionality.

logback configuration

1.application .properties

# Log printing information configuration
logging. config=classpath:logback-spring.xml

##2.logback-spring.xml

<?mybatis version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="60 seconds" debug="false">
    <contextName>logback</contextName>
    <!--输出到控制台-->
    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <!-- <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
             <level>ERROR</level>
         </filter>-->
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} %contextName [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <appender name="file" class="ch.qos.logback.core.rolling.RollingFileAppender"><!-- 日志文件会滚动 -->
        <!-- 文件路径 -->
        <file>./logs/gf_scanning.log</file><!-- 当前的日志文件存放路径 -->
        <!-- 日志滚动策略 -->
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- 历史日志文件的存放路径和名称 -->
            <fileNamePattern>./logs/gf_scanning.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <!-- 日志文件最大的保存历史 数量-->
            <maxHistory>30</maxHistory>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>10MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
        </rollingPolicy>
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} %contextName [%thread] %-5level %logger{36} - %msg%n</pattern> <!-- 日志文件中日志的格式 -->
        </encoder>
    </appender>
    <root level="info">
        <appender-ref ref="console"/>
        <appender-ref ref="file"/>
    </root>
</configuration>

Abnormal situation

Encountered something strange The problem is that after configuring logback according to the above configuration, most projects can run normally and save logs to files, but one project reports an error when starting.

java.lang.IllegalStateException: Could not initialize Logback logging from classpath:logback-spring.xml ... Caused by: ch.qos.logback.core.joran.spi.JoranException: Parser configuration error occurred

Logging system failed to initialize using configuration from 'classpath:logback-spring.xml'
java.lang.IllegalStateException: Could not initialize Logback logging from classpath:logback-spring.xml
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.loadConfiguration(LogbackLoggingSystem.java:168)
    at org.springframework.boot.logging.AbstractLoggingSystem.initializeWithSpecificConfig(AbstractLoggingSystem.java:66)
    at org.springframework.boot.logging.AbstractLoggingSystem.initialize(AbstractLoggingSystem.java:57)
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.initialize(LogbackLoggingSystem.java:132)
    at org.springframework.boot.context.logging.LoggingApplicationListener.initializeSystem(LoggingApplicationListener.java:316)
    at org.springframework.boot.context.logging.LoggingApplicationListener.initialize(LoggingApplicationListener.java:282)
    at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEnvironmentPreparedEvent(LoggingApplicationListener.java:240)
    at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:216)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:176)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:169)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:143)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:131)
    at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:85)
    at org.springframework.boot.SpringApplicationRunListeners.lambda$environmentPrepared$2(SpringApplicationRunListeners.java:66)
    at java.util.ArrayList.forEach(ArrayList.java:1257)
    at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:120)
    at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:114)
    at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:65)
    at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:339)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:297)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
    at cn.piesat.ScanningApplication.main(ScanningApplication.java:18)
Caused by: ch.qos.logback.core.joran.spi.JoranException: Parser configuration error occurred
    at ch.qos.logback.core.joran.event.SaxEventRecorder.buildSaxParser(SaxEventRecorder.java:89)
    at ch.qos.logback.core.joran.event.SaxEventRecorder.recordEvents(SaxEventRecorder.java:57)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:151)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:110)
    at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:53)
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.configureByResourceUrl(LogbackLoggingSystem.java:188)
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.loadConfiguration(LogbackLoggingSystem.java:165)
    ... 22 more
Caused by: org.xml.sax.SAXNotSupportedException: Feature: http://xml.org/sax/features/external-general-entities
    at org.apache.crimson.parser.XMLReaderImpl.setFeature(XMLReaderImpl.java:211)
    at org.apache.crimson.jaxp.SAXParserImpl.setFeatures(SAXParserImpl.java:143)
    at org.apache.crimson.jaxp.SAXParserImpl.7e51f00a783d7eb8f68358439dee7daf(SAXParserImpl.java:126)
    at org.apache.crimson.jaxp.SAXParserFactoryImpl.newSAXParserImpl(SAXParserFactoryImpl.java:113)
    at org.apache.crimson.jaxp.SAXParserFactoryImpl.setFeature(SAXParserFactoryImpl.java:141)
    at ch.qos.logback.core.joran.event.SaxEventRecorder.buildSaxParser(SaxEventRecorder.java:82)
    ... 28 more
Disconnected from the target VM, address: '127.0.0.1:64222', transport: 'socket'

Process finished with exit code 1

可能是由于jar包冲突，在pom文件中单独引入logback-core的依赖后，问题解决。

<!-- logback 日志 -->
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-core</artifactId>
    <version>1.1.7</version>
</dependency>
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.1.7</version>
    <exclusions>
        <exclusion>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
        </exclusion>
    </exclusions>
</dependency>

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