The Basic Settings of LogBack

In Java (Spring Boot) applications, the LogBack logging framework is often used to log, or it can be simplified with @Slf4j annotations in Lombok. To customize the output of the log, a configuration file named logback.xml is typically configured in the project.

pom.xml 文件

In the most basic case, a dependency library is required

<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.1.2</version>
</dependency>

If used with lombok, you can define two dependent libraries

<!-- Lombok and Log -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.16.14</version>
</dependency>
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.1.2</version>
</dependency>
<!-- End: Lombok and Log -->

Configuration in logback.xml

In maven projects, logback.xml files are typically placed in the project’s src/main/resources directory. Here are some basics to make it easy for you to quickly build your own project log configuration

The most basic configuration:

<configuration>
    <appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <pattern>%date [%thread] %-5level %logger{80} - %msg%n</pattern>
        </layout>
    </appender>
    <root>
        <level value="debug"/>
        <appender-ref ref="stdout"/>
    </root>
</configuration>

In the most basic configuration, we simply output the logs to the screen.

If we need to log the log in a local file, we usually need to add the following configuration information:

<substitutionProperty name="logbase" value="${user.dir}/logs/ "/>
<!-- File output log (file size policy for file output, more than the specified size to file backup) -->
<appender name="logfile"
          class="ch.qos.logback.core.rolling.RollingFileAppender">
    <Encoding>UTF-8</Encoding>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
        <File>${logbase}%d{yyyy-MM-dd}.log</File>
        <FileNamePattern>${logbase}.%d{yyyy-MM-dd}.log.zip
        </FileNamePattern>
    </rollingPolicy>
    <triggeringPolicy
            class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
        <MaxFileSize>2MB</MaxFileSize>
    </triggeringPolicy>
    <layout class="ch.qos.logback.classic.html.HTMLLayout">
        <pattern>%date%level%thread%10logger%file%line%msg</pattern>
    </layout>
</appender>

In the configuration, a variable named logbase is first declared, indicating the directory where the log files are stored. To prevent a single log file from being too large, a rollover mode of log files is declared.

After adding the file configuration, the full logback .xml as follows:

<configuration>
    <appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <pattern>%date [%thread] %-5level %logger{80} - %msg%n</pattern>
        </layout>
    </appender>

     <substitutionProperty name="logbase" value="${user.dir}/logs/ "/>
    <appender name="logfile"
              class="ch.qos.logback.core.rolling.RollingFileAppender">
        <Encoding>UTF-8</Encoding>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <File>${logbase}%d{yyyy-MM-dd}.log</File>
            <FileNamePattern>${logbase}.%d{yyyy-MM-dd}.log.zip
            </FileNamePattern>
        </rollingPolicy>
        <triggeringPolicy
                class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
            <MaxFileSize>2MB</MaxFileSize>
        </triggeringPolicy>
        <layout class="ch.qos.logback.classic.html.HTMLLayout">
            <pattern>%date%level%thread%10logger%file%line%msg</pattern>
        </layout>
    </appender>  

    <root>
        <level value="debug"/>
        <appender-ref ref="stdout"/>
        <appender-ref ref="logfile"/>
    </root>
</configuration>

Of course, we can also configure the log to be written to the database, and the following shows the configuration when storing the mySQL database as the log:

<appender name="DB" class="ch.qos.logback.classic.db.DBAppender">
    <connectionSource class="ch.qos.logback.core.db.DriverManagerConnectionSource">
         <driverClass>com.mysql.jdbc.Driver</driverClass>
         <url>jdbc:mysql://localhost:3306/logs</url>
         <user>logUser</user>
         <password>123456</password>
    </connectionSource>
</appender>