logback-spring.xml

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

  <!-- sets some suggested spring boot defaults -->
  <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
  <springProperty name="app_name" source="spring.application.name"/>

  <!--
    When springforge.logging.json-format in the Spring properties is set to true, the logs will be
    in Logstash JSON format. Otherwise, the logs will be standard colorized Spring Boot logging.
    The springProperty attribute makes the eh.logging.json-format spring property accessible here.
  -->
  <springProperty name="springforge_logging_json_format" source="springforge.logging.json-format"/>
  <if condition='p("springforge_logging_json_format").equals("true")'>
    <then>
      <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder class="net.logstash.logback.encoder.LogstashEncoder">
          <fieldNames>
            <timestamp>ts</timestamp>
          </fieldNames>
          <timeZone>UTC</timeZone>
          <customFields>{"app_name":"${app_name}"}</customFields>
        </encoder>
      </appender>
    </then>
    <else>
      <!-- includes an appender named CONSOLE -->
      <include resource="org/springframework/boot/logging/logback/console-appender.xml"/>
    </else>
  </if>

  <!-- register all appenders -->
  <root level="INFO">
    <appender-ref ref="CONSOLE"/>
  </root>
</configuration>