SpringBoot GraalVM Native Image编译阶段禁用Logback的方法

问题背景 #

编译SpringBoot GraalVM Native Image时，Logback会被自动调用初始化，编译日志示例如下：

[INFO] --- maven-surefire-plugin:3.5.0:test (default-test) @ myproject ---
[INFO] Tests are skipped.
[INFO] 
[INFO] --- spring-boot-maven-plugin:3.4.0-M3:process-aot (process-aot) @ myproject ---
15:32:58,782 |-INFO in ch.qos.logback.core.model.processor.AppenderModelHandler - Processing appender named [STDOUT]
15:32:58,785 |-INFO in ch.qos.logback.core.model.processor.AppenderModelHandler - About to instantiate appender of type [ch.qos.logback.core.ConsoleAppender]
15:32:58,795 |-INFO in ch.qos.logback.core.model.processor.ImplicitModelHandler - Assuming default type [ch.qos.logback.classic.encoder.PatternLayoutEncoder] for [encoder] property
15:32:58,800 |-INFO in ch.qos.logback.core.model.processor.ModelInterpretationContext@78641d23 - value "LOGS_HOST_IS_UNDEFINED" substituted for "${LOGS_HOST}"
[...]

构建过程中主应用会启动，Logback随之初始化，但构建阶段通常不需要配置生产环境的日志变量，而Logback配置文件中包含依赖环境变量的配置（比如Loki Appender）：

<appender name="LOKI" class="com.github.loki4j.logback.Loki4jAppender">
        <metricsEnabled>true</metricsEnabled>
        <http>
            <url>${LOGS_HOST}</url>
            <auth>
                <username>${LOGS_USER}</username>
                <password>${LOGS_TOKEN}</password>
            </auth>
        </http>
        <format>
            <label>

这会导致构建时因变量缺失触发初始化失败，错误日志如下：

Logging system failed to initialize using configuration from 'null'
java.lang.IllegalStateException: Could not initialize Logback logging from classpath:logback-spring.xml
    at org.springframework.boot.logging.logback.LogbackLoggingSystem.lambda$loadConfiguration$2(LogbackLoggingSystem.java:262)
[...]
Caused by: java.lang.IllegalArgumentException: URI with undefined scheme
    at java.net.http/jdk.internal.net.http.common.Utils.newIAE(Utils.java:378)
    at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.checkURI(HttpRequestBuilderImpl.java:79)
    at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:71)
    at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:43)
    at com.github.loki4j.client.http.JavaHttpClient.<init>(JavaHttpClient.java:50)
    [...]

直接移除Logback依赖会导致运行时丢失日志，不可行，以下是几种可行的解决方法：

可行解决方案 #

1. 构建阶段临时提供默认环境变量 #

在Maven构建命令中直接指定缺失的环境变量默认值，让Logback初始化时能获取到有效值，这些默认值仅用于构建阶段，不影响运行时：

mvn native:compile -DLOGS_HOST=http://localhost:3100 -DLOGS_USER=default -DLOGS_TOKEN=default

2. 通过Spring Profiles区分构建与运行环境 #

方法A：单独创建构建用Logback配置

创建一个简化的logback-build.xml配置文件，仅保留基础的ConsoleAppender，去掉依赖环境变量的Loki等第三方Appender：

<configuration>
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss} %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <root level="info">
        <appender-ref ref="STDOUT" />
    </root>
</configuration>

构建时指定使用该配置：

mvn native:compile -Dlogging.config=classpath:logback-build.xml

方法B：在主配置中用Profiles控制Appender加载

在主logback-spring.xml中，给依赖环境变量的Appender加上Spring Profile判断，仅在非构建环境加载：

<appender name="LOKI" class="com.github.loki4j.logback.Loki4jAppender">
    <springProfile name="!build">
        <metricsEnabled>true</metricsEnabled>
        <http>
            <url>${LOGS_HOST}</url>
            <auth>
                <username>${LOGS_USER}</username>
                <password>${LOGS_TOKEN}</password>
            </auth>
        </http>
        <format>
            <label>
                <!-- 其他配置 -->
            </label>
        </format>
    </springProfile>
</appender>

构建时激活build Profile：

mvn native:compile -Dspring.profiles.active=build

3. 禁用AOT阶段的日志初始化（Spring Boot 3.2+） #

Spring Boot 3.2及以上版本支持通过系统属性spring.aot.logging.enabled=false直接禁用AOT处理阶段的日志系统初始化，从根源上避免Logback在构建时启动：

mvn native:compile -Dspring.aot.logging.enabled=false

内容的提问来源于stack exchange，提问作者PatPanda