Logback Filter not working.

[SageJustus]

demo: https://github.com/SageJustus/question/tree/main/demo7

dependency

id("org.springframework.boot") version "3.4.4"

JpaFilter

package com.sage.local

import ch.qos.logback.classic.spi.ILoggingEvent
import ch.qos.logback.core.filter.Filter;
import ch.qos.logback.core.spi.FilterReply

class JpaFilter : Filter<ILoggingEvent>() {
    override fun decide(event: ILoggingEvent): FilterReply {
        val result = event.message.startsWith("Start")
        println(event.message)
        println(result)
        return if (result) FilterReply.DENY else FilterReply.NEUTRAL
    }
}

logback.xml

<configuration scan="true" debug="true">
    <!-- use Spring default values -->
    <include resource="org/springframework/boot/logging/logback/defaults.xml"/>

    <conversionRule conversionWord="clr" converterClass="org.springframework.boot.logging.logback.ColorConverter"/>

    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
            <level>${CONSOLE_LOG_THRESHOLD}</level>
        </filter>
        <encoder>
            <pattern>${CONSOLE_LOG_PATTERN}</pattern>
            <charset>${CONSOLE_LOG_CHARSET}</charset>
        </encoder>
    </appender>

    <appender name="Jpa" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="com.sage.local.JpaFilter"/>
        <encoder>
            <pattern>${CONSOLE_LOG_PATTERN}</pattern>
            <charset>${CONSOLE_LOG_CHARSET}</charset>
        </encoder>
    </appender>

    <logger name="com.sage.local.Demo7ApplicationKt" level="info">
        <appender-ref ref="Jpa"/>
    </logger>

    <root level="error">
        <appender-ref ref="CONSOLE"/>
    </root>

</configuration>

Start the springboot project. output:

Starting Demo7ApplicationKt using Java 21.0.5 with PID 48596 (C:\JavaProjects\question\demo7\build\classes\kotlin\main started by Administrator in C:\JavaProjects\question\demo7)
true
2025-04-07T19:55:52.014+08:00  INFO 48596 --- [           main] com.sage.local.Demo7ApplicationKt        : Starting Demo7ApplicationKt using Java 21.0.5 with PID 48596 (C:\JavaProjects\question\demo7\build\classes\kotlin\main started by Administrator in C:\JavaProjects\question\demo7)

The returned FilterReply.DENY value has no effect.

When I use logback alone, the filter works well

[mhalbritter]

Does it work if you use logback-spring.xml instead of logback.xml?

[SageJustus]

Does it work if you use logback-spring.xml instead of logback.xml?

@mhalbritter use logback-spring.xml not working.

JpaFilter#decide method has been run, just return value not working.

[mhalbritter]

I can't imagine this setup to be working on Logback without Spring Boot either. Your problem is that loggers are additive: https://logback.qos.ch/manual/configuration.html#cumulative

By default, appenders are cumulative: a logger will log to the appenders attached to itself (if any) as well as all the appenders attached to its ancestors. Thus, attaching the same appender to multiple loggers will cause logging output to be duplicated.

Your filter is working, it's just that the CONSOLE logger is printing the line again.

Do it like this and it works:

    <logger name="com.sage.local.Demo7ApplicationKt" level="info" additivity="false">
        <appender-ref ref="Jpa"/>
    </logger>