Java无法访问Kotlin的伙伴

Question

我试图在java代码中使用kotlinx序列化。我遇到的问题是，我不能在java代码中使用Companion对象来访问由kotlin序列化插件生成的静态序列化器()方法。下面是标记可序列化类的kotlin代码：

@kotlinx.serialization.Serializable
data class MyData(private val data: String)

我的mavem pom.xml文件如下所示

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>org.example</groupId>
<artifactId>TestProject</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
    <maven.compiler.source>18</maven.compiler.source>
    <maven.compiler.target>18</maven.compiler.target>
    <kotlin.version>1.7.0</kotlin.version>
    <serialization.version>1.3.3</serialization.version>
</properties>

<dependencies>
    <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>
    <!-- https://mvnrepository.com/artifact/org.jetbrains.kotlinx/kotlinx-serialization-protobuf-jvm -->
    <dependency>
        <groupId>org.jetbrains.kotlinx</groupId>
        <artifactId>kotlinx-serialization-json-jvm</artifactId>
        <version>1.3.3</version>
    </dependency>

</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-plugin</artifactId>
            <version>${kotlin.version}</version>
            <executions>
                <execution>
                    <id>compile</id>
                    <phase>compile</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
                <execution>
                    <id>test-compile</id>
                    <phase>test-compile</phase>
                    <goals>
                        <goal>test-compile</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <jvmTarget>1.8</jvmTarget>
                <compilerPlugins>
                    <plugin>kotlinx-serialization</plugin>
                </compilerPlugins>
            </configuration>
            <dependencies>
                <dependency>
                    <groupId>org.jetbrains.kotlin</groupId>
                    <artifactId>kotlin-maven-serialization</artifactId>
                    <version>${kotlin.version}</version>
                </dependency>
            </dependencies>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>17</source>
                <target>17</target>
            </configuration>
        </plugin>
    </plugins>
</build>

我编写的java代码如下(它不编译，因为它找不到Companion对象)：

public class Main {

public static void main(String[] args) {
    MyData.Companion.serializer();
}

}

我可以访问其他kotlin类的Companion对象(例如，Companio.serializer() of JsonElement)，但不能访问由kotlinx序列化插件自动生成的Companion。另外，自动生成的目标类包含Companion对象，下面是代码：

    // IntelliJ API Decompiler stub source generated from a class file
// Implementation of methods is not available

@kotlinx.serialization.Serializable public final data class MyData public constructor(data: kotlin.String) {
    public companion object {
    }

    @kotlin.Deprecated public constructor(seen1: kotlin.Int, data: kotlin.String?, serializationConstructorMarker: kotlinx.serialization.internal.SerializationConstructorMarker?) { /* compiled code */ }

    private final val data: kotlin.String /* compiled code */

    private final operator fun component1(): kotlin.String { /* compiled code */ }

    @kotlin.Deprecated public object `$serializer` : kotlinx.serialization.internal.GeneratedSerializer<MyData> {
    }
}

UPD:我可以访问我尝试过的自动生成的复制方法。

UPD:这是intellij的截图

​

Answer 1

这似乎只是IntelliJ的Kotlin编译器插件的一个问题。尽管IDEA认为您的Java代码中有错误，但实际上仍然可以在命令行上编译它(或者使用Maven或Gradle)，并且运行得很好。