Why my java app using logback in docker container print nothing ?

[xingya1822]

the logback.xml is in the jar:

the logback.xml just using console to log:

<configuration>
  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
    </encoder>
  </appender>

  <root level="debug">
    <appender-ref ref="STDOUT" />
  </root>
</configuration>

but why my container print nothing, except this line:

SLF4J(I): Connected with provider of type [ch.qos.logback.classic.spi.LogbackServiceProvider]

I am using 1.5.7 version.

maybe this is a silly question, please someone help.