需要將日誌列印在本專案中，於是調整logback.xml中日誌生成路徑，並在application.propeties中添加了變數。。結果讀取不到。並且生成的log目錄為XXX_IS_UNDEFINED。

主要問題就是沒有讀取到application.properties檔案，所以解決辦法為在logback.xml中新增一個屬性

<property resource="application.properties" />

application.properties：

loggingroot  = ${user.dir}/output

logback.xml如下：

 <?xml version="1.0" encoding="UTF-8"?>
 

<configuration>
    <include resource="org/springframework/boot/logging/logback/defaults.xml" />
    <property resource="application.properties" />

    <property name="APP_NAME" value="demo" />
    <property name="LOG_PATH" value="${loggingRoot}/logs" />
    <property name="LOG_FILE"
 
 value="${LOG_PATH}/application.log" />

    <appender name="APPLICATION"
              class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_FILE}</file>
        <encoder>
            <pattern>${FILE_LOG_PATTERN}</pattern>
        </encoder
 
>
        <rollingPolicy
                class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <maxHistory>7</maxHistory>
            <maxFileSize>50MB</maxFileSize>
            <totalSizeCap>20GB</totalSizeCap>
        </rollingPolicy>
    </appender>

    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>${CONSOLE_LOG_PATTERN}</pattern>
            <charset>utf8</charset>
        </encoder>
    </appender>

    <root level="INFO">
        <appender-ref ref="CONSOLE" />
        <appender-ref ref="APPLICATION" />
    </root>

</configuration>