Spring Modulith导致@ConfigurationProperties类CGLIB子类生成异常

问题描述 #

我们基于Kotlin搭建了Spring Boot项目，使用Spring Modulith管控模块边界，包结构如下：

my.company.myapp
-> MySpringBootApp
-> config
   -> SpringSecurityConfig.kt
   -> SecurityProperties.kt
-> usecase1
   -> <fleshed out implementation for use case 1>
-> usecase2..usecaseN
   -> no implementation as of yet

SecurityProperties类代码：

@ConfigurationProperties(prefix = "security")
data class SecurityProperties(
    val users: List<User>
)

data class User(
    val username: String,
    val password: String,
    val roles: Set<Role>
)

enum class Role {
    MONITORING,
    API_USER
}

使用TestContainers时，在src/test/kotlin编写了本地启动类：

object MyLocalSpringBootApp {

    @JvmStatic
    fun main(args: Array<String>) {
        fromApplication<MySpringBootApp>()
            .with(ContainersConfig::class.java)
            .run(*args)
    }
}

启动时抛出异常：

...
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class my.company.myapp.config.SecurityProperties: Common causes of this problem include using a final class or a non-visible class
    at org.springframework.aop.framework.CglibAopProxy.buildProxy(CglibAopProxy.java:227)
    at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:160)
    at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:110)
    at org.springframework.modulith.observability.ModuleTracingSupport.addAdvisor(ModuleTracingSupport.java:58)
    at org.springframework.modulith.observability.ModuleTracingSupport.addAdvisor(ModuleTracingSupport.java:42)
    at org.springframework.modulith.observability.ModuleTracingBeanPostProcessor.lambda$postProcessAfterInitialization$0(ModuleTracingBeanPostProcessor.java:92)
    at java.base/java.util.Optional.map(Optional.java:260)
    at org.springframework.modulith.observability.ModuleTracingBeanPostProcessor.postProcessAfterInitialization(ModuleTracingBeanPostProcessor.java:87)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:437)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1776)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:599)
    ... 51 common frames omitted

已使用带spring插件的kotlin-maven-plugin，理论上不可变Kotlin数据类不应出现final类问题。

临时解决方法 #

• 移除pom.xml中所有Spring Modulith依赖，应用可正常启动；
• 为SecurityProperties添加冗余@Configuration注解并保留Spring Modulith依赖，应用可正常启动；
• 将"config"下的类移至"usecase1"目录，应用可正常启动，但推测实现其他用例后会失效。

疑问 #

该问题是配置/使用不当，还是Spring Modulith的Bug？

更多细节 #

• Spring Boot 3.2.1
• Spring Modulith 1.1.2
• Kotlin 1.9.21
• kotlin-maven-plugin配置：

<plugin>
        <groupId>org.jetbrains.kotlin</groupId>
        <artifactId>kotlin-maven-plugin</artifactId>
        <version>${kotlin.version}</version>
        <executions>
            <execution>
                <id>compile</id>
                <goals>
                    <goal>compile</goal>
                </goals>
                <configuration>
                    <sourceDirs>
                        <sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
                    </sourceDirs>
                </configuration>
            </execution>
            <execution>
                <id>test-compile</id>
                <goals>
                    <goal>test-compile</goal>
                </goals>
                <configuration>
                    <sourceDirs>
                        <sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
                    </sourceDirs>
                </configuration>
            </execution>
        </executions>
        <configuration>
            <args>
                <arg>-Xjsr305=strict</arg>
                <arg>-opt-in=kotlin.RequiresOptIn</arg>
                <arg>-java-parameters</arg>
            </args>
            <compilerPlugins>
                <plugin>spring</plugin>
                <plugin>jpa</plugin>
            </compilerPlugins>
        </configuration>
        <dependencies>
            <dependency>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-allopen</artifactId>
                <version>${kotlin.version}</version>
            </dependency>
            <dependency>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-noarg</artifactId>
                <version>${kotlin.version}</version>
            </dependency>
        </dependencies>
    </plugin>

根因分析 #

这并非Spring Modulith的Bug，而是Kotlin allopen插件的默认配置未覆盖@ConfigurationProperties注解导致的：

1. Spring Modulith的ModuleTracingBeanPostProcessor会为跨模块调用的Bean生成CGLIB代理，用于模块间调用追踪；
2. Kotlin数据类默认是final的，spring插件（即allopen）仅会自动开放带有@Configuration、@Controller、@Service等Spring stereotype注解的类；
3. @ConfigurationProperties不在allopen默认开放的注解列表中，因此SecurityProperties仍为final类，CGLIB无法生成其子类，触发异常。

临时解决方法的原理：

• 移除Spring Modulith依赖后，ModuleTracingBeanPostProcessor不存在，不会触发代理创建；
• 添加@Configuration注解后，allopen插件将类改为非final，CGLIB可生成代理；
• 移至usecase1目录后，该类被识别为模块内部Bean，Spring Modulith暂时跳过代理逻辑，但后续跨模块调用时仍可能复现问题。

正确解决方案 #

方案1：让@ConfigurationProperties类被allopen插件处理

修改kotlin-maven-plugin的配置，添加@ConfigurationProperties到开放注解列表：

<plugin>
    <groupId>org.jetbrains.kotlin</groupId>
    <artifactId>kotlin-maven-plugin</artifactId>
    <!-- 其他配置不变 -->
    <configuration>
        <!-- 其他args不变 -->
        <compilerPlugins>
            <plugin>spring</plugin>
            <plugin>jpa</plugin>
        </compilerPlugins>
        <pluginOptions>
            <option>spring:annotation=org.springframework.boot.context.properties.ConfigurationProperties</option>
        </pluginOptions>
    </configuration>
    <!-- 其他依赖不变 -->
</plugin>

此方案会自动将所有带有@ConfigurationProperties的类改为非final，从根本上解决CGLIB代理问题。

方案2：排除SecurityProperties被模块追踪代理

自定义Spring配置，让ModuleTracingBeanPostProcessor跳过该类：

@Configuration
class CustomModuleTracingConfiguration {
    @Bean
    fun moduleTracingBeanPostProcessor(applicationModules: ApplicationModules): ModuleTracingBeanPostProcessor {
        return ModuleTracingBeanPostProcessor(applicationModules)
            .excludeBeansOfType(SecurityProperties::class.java)
    }
}

方案3：将config包标记为共享模块

在Spring Modulith中，共享模块的Bean不会被视为跨模块调用的代理目标。可通过application-modules.properties配置：

spring.modulith.modules.config.name=config
spring.modulith.modules.config.shared=true

或在包上添加@Module(shared = true)注解（需确保包被Spring扫描到）。

内容的提问来源于stack exchange，提问作者Oliver Plaehn