Logback JsonLayout printing all logs on the same line

You need to set appendLineSeparator option to true for ch.qos.logback.contrib.json.classic.JsonLayout. Example of this:

<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <layout class="ch.qos.logback.contrib.json.classic.JsonLayout">
        <jsonFormatter class="ch.qos.logback.contrib.jackson.JacksonJsonFormatter" />
        <timestampFormat>yyyy-MM-dd' 'HH:mm:ss.SSS</timestampFormat>
        <appendLineSeparator>true</appendLineSeparator>
    </layout>
</appender>

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