Spring Boot 3升级遇LoggerFactory冲突问题求助

问题背景 #

我们正将应用升级至Spring Boot 3，运行时出现LoggerFactory冲突问题。通过Slf4j使用Logback作为日志实现，引入了spring-boot-starter-logging模块，未在build.gradle中指定Slf4j或Logback的版本。

依赖详情 #

集成测试运行时类路径的日志相关依赖如下：

integrationTestRuntimeClasspath - Runtime classpath of source set 'integration test'.
+--- net.logstash.logback:logstash-logback-encoder:6.6
|    \--- com.fasterxml.jackson.core:jackson-databind:2.12.0 -> 2.14.2
|         +--- com.fasterxml.jackson.core:jackson-annotations:2.14.2
|         |    \--- com.fasterxml.jackson:jackson-bom:2.14.2
|         |         +--- com.fasterxml.jackson.core:jackson-annotations:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.core:jackson-core:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.core:jackson-databind:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.datatype:jackson-datatype-guava:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.datatype:jackson-datatype-jdk8:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.module:jackson-module-parameter-names:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.dataformat:jackson-dataformat-cbor:2.14.2 (c)
|         |         +--- com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.14.2 (c)
|         |         \--- com.fasterxml.jackson.datatype:jackson-datatype-joda:2.14.2 (c)
|         +--- com.fasterxml.jackson.core:jackson-core:2.14.2
|         |    \--- com.fasterxml.jackson:jackson-bom:2.14.2 (*)
|         \--- com.fasterxml.jackson:jackson-bom:2.14.2 (*)
+--- org.springframework.boot:spring-boot-starter-logging -> 3.0.5
|    \--- ch.qos.logback:logback-classic:1.4.6
|         +--- ch.qos.logback:logback-core:1.4.6
|         \--- org.slf4j:slf4j-api:2.0.4 -> 2.0.7
+--- org.springframework:spring-context -> 6.0.7
|    +--- org.springframework:spring-aop:6.0.7
|    |    +--- org.springframework:spring-beans:6.0.7
|    |    |    \--- org.springframework:spring-core:6.0.7
|    |    |         \--- org.springframework:spring-jcl:6.0.7
|    |    \--- org.springframework:spring-core:6.0.7 (*)
|    +--- org.springframework:spring-beans:6.0.7 (*)
|    +--- org.springframework:spring-core:6.0.7 (*)
|    \--- org.springframework:spring-expression:6.0.7
|         \--- org.springframework:spring-core:6.0.7 (*)
+--- org.springframework:spring-beans -> 6.0.7 (*)
+--- com.fasterxml.jackson.core:jackson-databind:{strictly 2.14.2} -> 2.14.2 (*)
+--- com.fasterxml.jackson.core:jackson-annotations:{strictly 2.14.2} -> 2.14.2 (*)
+--- org.apache.tomcat.embed:tomcat-embed-core:9.0.69
|    \--- org.apache.tomcat:tomcat-annotations-api:9.0.69 -> 10.1.7
+--- commons-logging:commons-logging:1.1.3 -> 1.2

现有配置 #

多模块构建的所有模块中应用了以下排除规则和依赖：

configurations.all {
    // Short version cache so we don't accidentally use old versions
    resolutionStrategy.cacheDynamicVersionsFor 10, 'minutes'
    exclude group: 'org.apache.logging.log4j', module: 'log4j-to-slf4j'
    exclude group: 'org.apache.logging.log4j', module: 'log4j-api'
    exclude group: 'org.slf4j', module: 'jul-to-slf4j'
    exclude group: 'org.slf4j', module: 'slf4j-log4j'
    exclude group: 'org.slf4j', module: 'slf4j-log4j12'
}

dependencies {
    implementation 'net.logstash.logback:logstash-logback-encoder:6.6'
    implementation 'org.springframework.boot:spring-boot-starter-logging'

错误信息 #

运行集成测试时出现如下错误：

Caused by: java.lang.IllegalArgumentException: LoggerFactory is not a Logback LoggerContext but Logback is on the classpath. Either remove Logback or the competing implementation (class org.slf4j.helpers.SubstituteLoggerFactory loaded from file: .../.gradle/caches/modules-2/files-2.1/org.slf4j/slf4j-api/2.0.7/41eb7184ea9d556f23e18b5cb99cad1f8581fc00/slf4j-api-2.0.7.jar). If you are using WebLogic you will need to add 'org.slf4j' to prefer-application-packages in WEB-INF/weblogic.xml: org.slf4j.helpers.SubstituteLoggerFactory

奇怪的是，只有部分集成测试受影响，其余测试运行正常。

编辑：调试发现org.slf4j.LoggerFactory初始化时返回的是SubstituteLogger。

解决方案建议 #

1. 检查类路径加载顺序 #

部分测试失败说明类加载顺序存在差异，SubstituteLoggerFactory被优先加载。可以通过以下方式排查：

• 为失败的测试添加JVM参数-verbose:class，查看日志类的加载顺序，确认是否有其他类库提前触发了SLF4J初始化。
• 检查测试类的依赖，是否某个测试引入了特殊依赖，导致SLF4J在Logback之前被初始化。

2. 强制SLF4J与Logback版本对齐 #

Spring Boot 3.0.5依赖的SLF4J版本是2.0.4，当前被升级到了2.0.7，虽版本兼容，但可强制锁定版本避免潜在问题：

configurations.all {
    resolutionStrategy.force 'org.slf4j:slf4j-api:2.0.4'
    resolutionStrategy.force 'ch.qos.logback:logback-classic:1.4.6'
    resolutionStrategy.force 'ch.qos.logback:logback-core:1.4.6'
}

3. 排查测试初始化逻辑 #

部分测试可能在Spring Boot上下文初始化前就尝试获取Logger，此时Logback还未加载，SLF4J会用SubstituteLoggerFactory作为占位符。可以：

• 检查测试类是否使用了@BeforeClass等提前执行的代码，其中包含日志操作。
• 确保所有测试都通过Spring Boot的@SpringBootTest或相关注解初始化上下文，保证Logback先完成加载。

4. 移除commons-logging依赖 #

Spring的spring-jcl模块已替代commons-logging，但当前依赖中仍有commons-logging:1.2，可排除该依赖避免冲突：

configurations.all {
    exclude group: 'commons-logging', module: 'commons-logging'
}

5. 升级logstash-logback-encoder版本 #

当前使用的logstash-logback-encoder 6.6版本需确认与Logback 1.4.6（Spring Boot 3.0.5依赖）的兼容性，可升级到适配版本（如7.4及以上）：

implementation 'net.logstash.logback:logstash-logback-encoder:7.4'

内容的提问来源于stack exchange，提问作者Ben Green