Spring Boot 2.7.7-SNAPSHOT Logback配置报错：找不到指定Appender

问题 #

使用Spring Boot v2.7.7-SNAPSHOT，尝试从application.yaml读取配置到logback-spring.xml时，始终报错：

Could not find an appender named [appender_name_IS_UNDEFINED].

已附相关配置文件及错误堆栈，按错误提示调整配置后仍未解决。

application.yaml 配置 #

server:
  port: 80
app:
  logging-to:console
logging:
  level:
    "[org.springframework]": INFO
    "[com.med4pan.cloudapp]": DEBUG

logback-spring.xml 配置 #

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org.springframework.boot/looging/logback/defaults.xml"/>
    <include resource="org.springframework.boot/logging/logback/console-appender.xml" />
    <springProperty scope="context" name="CONSOLE_PATTERN" source="application.console-pattern"/>
    <springProperty scope="context" name="appender_name" source="app.logging-to"/>
    
    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%black(%d{ISO8601}) %highlight(%-5level) [%blue(%t)] %yellow(%C{1.}): %msg%n%throwable</pattern>
            <charset>UTF-8</charset>
        </encoder>
    </appender>

    <appender name="file" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>Cloud-Panel-Logs.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>Cloud-Panel-Logs.%d{yyyy-MM}.log</fileNamePattern>
            <maxHistory>6</maxHistory>
            <totalSizeCap>1GB</totalSizeCap>
        </rollingPolicy>
        <encoder>
            <pattern>%black(%d{ISO8601}) %highlight(%-5level) [%blue(%t)] %yellow(%C{1.}): %msg%n%throwable</pattern>    
            <charset>UTF-8</charset>
        </encoder>
    </appender>

    <appender name="ASYNC_CONSOLE" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="${appender_name}"/>
        <discardingThreshold>0</discardingThreshold>
        <queueSize>100000</queueSize>
        <includeCallerData>false</includeCallerData>
        <neverBlock>false</neverBlock>
    </appender>

    <root level="INFO">
        <appender-ref ref="ASYNC_CONSOLE"/>
    </root>
    <logger name="org.springframework.web" level="DEBUG"/>
</configuration>

错误堆栈 #

Caused by: java.lang.IllegalStateException: java.lang.IllegalStateException: Logback configuration error detected: 
ERROR in ch.qos.logback.core.joran.action.AppenderRefAction - Could not find an appender named [appender_name_IS_UNDEFINED]. Did you define it below instead of above in the configuration file?
ERROR in ch.qos.logback.core.joran.action.AppenderRefAction - See http://logback.qos.ch/codes.html#appender_order for more details.
ERROR in ch.qos.logback.classic.AsyncAppender[ASYNC_CONSOLE] - No attached appenders found.
    at org.springframework.boot.context.logging.LoggingApplicationListener.initializeSystem(LoggingApplicationListener.java:344)
    at org.springframework.boot.context.logging.LoggingApplicationListener.initialize(LoggingApplicationListener.java:298)
    at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEnvironmentPreparedEvent(LoggingApplicationListener.java:246)
    at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:223)
    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.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    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:343)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:301)
    at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:136)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:141)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:90)
    ... 87 common frames omitted

解决方案 #

• 修正YAML格式错误：application.yaml中logging-to:console缺少冒号后的空格，YAML语法要求键值对冒号后必须加空格，改为：

  app:
    logging-to: console
  

  这是导致配置无法读取、出现appender_name_IS_UNDEFINED的核心原因。

• 修复logback配置文件拼写错误：logback-spring.xml中第一个include标签的looging拼写错误，应为logging，修正后：

  <include resource="org.springframework.boot/logging/logback/defaults.xml"/>
  

  错误拼写会导致默认配置加载失败，影响Spring上下文对logback配置的解析。

• 可选：添加默认值避免未配置时出错：在springProperty标签中添加defaultValue属性，防止配置未正确加载时出现类似错误，例如：

  <springProperty scope="context" name="appender_name" source="app.logging-to" defaultValue="console"/>
  

完成以上修改后，重启应用即可正常读取配置并加载对应的appender。

内容的提问来源于stack exchange，提问作者Hridoy