Springboot項目啓動報錯：Failed to create converter for [%clr] keyword

完整報錯信息如下：

Exception in thread "main" java.lang.IllegalStateException: Logback configuration error detected: 
ERROR in ch.qos.logback.core.pattern.parser.Compiler@7a362b6b - There is no conversion class registered for composite conversion word [clr]
ERROR in ch.qos.logback.core.pattern.parser.Compiler@7a362b6b - Failed to create converter for [%clr] keyword
ERROR in ch.qos.logback.core.pattern.parser.Compiler@7a362b6b - There is no conversion class registered for composite conversion word [clr]
ERROR in ch.qos.logback.core.pattern.parser.Compiler@7a362b6b - Failed to create converter for [%clr] keyword
	at org.springframework.boot.logging.logback.LogbackLoggingSystem.loadConfiguration(LogbackLoggingSystem.java:166)
	at org.springframework.boot.logging.AbstractLoggingSystem.initializeWithConventions(AbstractLoggingSystem.java:82)
	at org.springframework.boot.logging.AbstractLoggingSystem.initialize(AbstractLoggingSystem.java:60)
	at org.springframework.boot.logging.logback.LogbackLoggingSystem.initialize(LogbackLoggingSystem.java:114)
	at org.springframework.boot.context.logging.LoggingApplicationListener.initializeSystem(LoggingApplicationListener.java:264)
	at org.springframework.boot.context.logging.LoggingApplicationListener.initialize(LoggingApplicationListener.java:237)
	at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEnvironmentPreparedEvent(LoggingApplicationListener.java:200)
	at org.springframework.boot.context.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:173)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
	at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:74)
	at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:54)
	at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:358)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:317)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1255)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1243)
	at com.kaka.jtest.springboot.Application.main(Application.java:24)

前因

看到網上說，可以指定日誌的顏色。使用方法：在日誌配置文件中的pattern節點中，加上%clr即可，格式：%clr(日誌內容){顏色}

支持的顏色：

• blue
• cyan
• faint
• green
• magenta
• red
• yellow

於是我就在控制檯輸出試了試，沒想到項目起不來了。日誌配置如下，主要看pattern中的內容：

<!--1.控制檯輸出日誌 ConsoleAppender-->
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <!-- encoder 默認配置爲PatternLayoutEncoder -->
    <encoder>
        <pattern>%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){green}---%magenta([%thread])---%clr(%-5level)---%blue([%c])---%green([%L])---[traceId:%X{traceId}]---[%msg]%n</pattern>
    </encoder>
</appender>

解決

日誌配置文件（logback-spring.xml）中，引入springboot的默認日誌配置。

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

原理

pattern節點中使用百分號（%）開頭的關鍵字，都會對應一個轉換器。這些轉換器可以自己擴展開發，但需要在配置文件中指定關鍵字對應的轉換器類。這也就能解釋報錯中的信息：

There is no conversion class registered for composite conversion word [clr]

所以springboot中顏色關鍵字clr，也應該指定一個對應的轉換器類，否則就會報找不到對應的轉換器的錯誤！其實clr的轉換器類springboot已經開發的，我們僅需指定下即可。我們看下引入的文件：org/springframework/boot/logging/logback/defaults.xml 就明白了。

我們引入的這個defaults.xml文件中，springboot已經給我們制定好clr對應的轉換器類了。