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Java 9模块下Kotlin项目同模块符号访问报错的非导出包解决办法

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API 探路者
2026-8-25
问题描述

我有一个极简Kotlin演示项目，完整代码如下：

package com.example.demo

import io.swagger.annotations.Api

@Api(tags = [API_NAME])
class DemoClass

const val API_NAME = "demo"

fun main() = println("Hello World!")

原本运行正常，添加Java 9模块系统后，在src/main/kotlin下创建了module-info.java，内容如下：

module com.example.demo {
    requires swagger.annotations;
    requires kotlin.stdlib;
}

出现编译错误：

E:\demo\src\main\kotlin\com\example\demo\DemoClass.kt:[5,18] Symbol is declared in module 'com.example.demo' which does not export package 'com.example.demo'

问题出在@Api注解中使用的API_NAME常量。虽然在module-info.java中导出com.example.demo包可以解决问题，但不想这么做，求其他解决办法。

使用Maven作为构建工具，pom.xml配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>11</java.version>
        <kotlin.version>1.7.10</kotlin.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>io.swagger</groupId>
            <artifactId>swagger-annotations</artifactId>
            <version>1.6.6</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-test</artifactId>
            <version>${kotlin.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <sourceDirectory>src/main/kotlin</sourceDirectory>
        <testSourceDirectory>src/test/kotlin</testSourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <args>
                        <arg>-Xjsr305=strict</arg>
                    </args>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                    </compilerPlugins>
                    <jvmTarget>1.8</jvmTarget>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

</project>

mvn clean install -e的完整输出：

[INFO] Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO]
[INFO] --------------------------< com.example:demo >--------------------------
[INFO] Building demo 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:3.2.0:clean (default-clean) @ demo ---
[INFO] Deleting E:\demo\target
[INFO]
[INFO] --- maven-resources-plugin:3.2.0:resources (default-resources) @ demo ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Using 'UTF-8' encoding to copy filtered properties files.
[INFO] Copying 1 resource
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.10.1:compile (default-compile) @ demo ---
[INFO] Required filename-based automodules detected: [swagger-annotations-1.6.6.jar]. Please don't publish this project to a public artifact repository!
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to E:\demo\target\classes
[INFO]
[INFO] --- kotlin-maven-plugin:1.7.10:compile (compile) @ demo ---
[INFO] Applied plugin: 'spring'
[ERROR] E:\demo\src\main\kotlin\com\example\demo\DemoClass.kt: (5, 18) Symbol is declared in module 'com.example.demo' which does not export package 'com.example.demo'
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  3.825 s
[INFO] Finished at: 2022-07-16T01:49:05+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.jetbrains.kotlin:kotlin-maven-plugin:1.7.10:compile (compile) on project demo: Compilation failure
[ERROR] E:\demo\src\main\kotlin\com\example\demo\DemoClass.kt:[5,18] Symbol is declared in module 'com.example.demo' which does not export package 'com.example.demo'
[ERROR]
[ERROR] -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.jetbrains.kotlin:kotlin-maven-plugin:1.7.10:compile (compile) on project demo: Compilation failure
E:\demo\src\main\kotlin\com\example\demo\DemoClass.kt:[5,18] Symbol is declared in module 'com.example.demo' which does not export package 'com.example.demo'

    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:215)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:972)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:293)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:196)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
Caused by: org.jetbrains.kotlin.maven.KotlinCompilationFailureException: Compilation failure
E:\demo\src\main\kotlin\com\example\demo\DemoClass.kt:[5,18] Symbol is declared in module 'com.example.demo' which does not export package 'com.example.demo'

    at org.jetbrains.kotlin.maven.MavenPluginLogMessageCollector.throwKotlinCompilerException (MavenPluginLogMessageCollector.java:111)
    at org.jetbrains.kotlin.maven.KotlinCompileMojoBase.execute (KotlinCompileMojoBase.java:212)
    at org.jetbrains.kotlin.maven.K2JVMCompileMojo.execute (K2JVMCompileMojo.java:222)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:972)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:293)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:196)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
[ERROR]
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
解决方案

有几种不需要导出整个包的解决办法：

1. 使用字符串字面量替代常量

直接在@Api注解中写字符串字面量，绕过模块访问检查：

@Api(tags = ["demo"])
class DemoClass

这种方法最简单，适合常量值不需要复用的场景。

2. 将常量移至未命名包（默认包）

把API_NAME常量放到默认包中，默认包的内容对模块内部是可见的：

// 去掉package声明，直接定义常量
const val API_NAME = "demo"

然后在DemoClass.kt中引用：

package com.example.demo

import io.swagger.annotations.Api
import API_NAME

@Api(tags = [API_NAME])
class DemoClass

fun main() = println("Hello World!")

注意：默认包在模块化系统中不推荐长期使用，但能快速解决问题。

3. 使用opens指令而非exports

如果需要保留常量在原包中，但不想导出整个包供外部模块调用，可以使用opens指令开放包给反射访问——因为Swagger注解在运行时需要反射读取值，opens只允许反射访问，不会让包内的类/常量被其他模块直接引用：

module com.example.demo {
    requires swagger.annotations;
    requires kotlin.stdlib;
    opens com.example.demo to swagger.annotations;
}

这种方式更符合模块化设计原则，既满足Swagger的反射需求，又不会把包暴露给所有模块。

4. 把常量放在专门的开放包中

创建一个新的包，比如com.example.demo.constants，在module-info.java中导出或开放这个包，把API_NAME移到该包下：

// com/example/demo/constants/ApiConstants.kt
package com.example.demo.constants

const val API_NAME = "demo"

修改module-info.java：

module com.example.demo {
    requires swagger.annotations;
    requires kotlin.stdlib;
    opens com.example.demo.constants to swagger.annotations;
    // 或者如果不需要反射限制，直接导出：exports com.example.demo.constants;
}

然后在DemoClass中引用：

package com.example.demo

import io.swagger.annotations.Api
import com.example.demo.constants.API_NAME

@Api(tags = [API_NAME])
class DemoClass

fun main() = println("Hello World!")

这种方式更规整，适合有多个需要对外暴露的常量的场景。

内容的提问来源于stack exchange，提问作者findusl

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最近更新时间：2026.08.25 20:39:19