java - 有没有办法在 GraalVM 原生镜像中使用 kotlin.random.Random

Question

我尝试使用 Kotlin 构建一个简单的应用程序，该应用程序在 GraalVM native 镜像上使用 kotlin.random.Random 类。
但这在运行时失败。堆栈跟踪见下文。

作为一种解决方法，您可以使用 java 标准 java.util.Random 类。

有人能告诉我如何使用 Kotlin 类型吗？

App.kt

import kotlin.random.Random

fun main(args: Array<String>) {
   println(Random.nextInt())
}

Dockerfile

############################################################################
# Graal Native Image Early-Access Build
#
# Make sure you configured Docker to use at least 6gb ram!
# build from project root dir with: docker build -t example-kotlin-random-graalvm-native:1.0.0-SNAPSHOT .
# run with: docker run -d example-kotlin-random-graalvm-native:1.0.0-SNAPSHOT
############################################################################
#####
# The builder image to build the native app
#####
FROM findepi/graalvm:native as builder
LABEL stage=builder

WORKDIR /builder
COPY ./build/libs/app-all.jar ./app.jar
RUN native-image \
    --no-fallback \
    --static \
    -jar app.jar

#####
# The actual image to run
#####
FROM alpine:3.9
RUN apk --no-cache add ca-certificates

# App
WORKDIR /app
COPY --from=builder /builder/app .
EXPOSE $PORT
ENTRYPOINT ["./app"]

运行时错误

Exception in thread "main" java.lang.ExceptionInInitializerError

at com.oracle.svm.core.hub.ClassInitializationInfo.initialize(ClassInitializationInfo.java:290)

at java.lang.Class.ensureInitialized(DynamicHub.java:475)

at kotlin.random.Random.<clinit>(Random.kt:242)

at com.oracle.svm.core.hub.ClassInitializationInfo.invokeClassInitializer(ClassInitializationInfo.java:350)

at com.oracle.svm.core.hub.ClassInitializationInfo.initialize(ClassInitializationInfo.java:270)

at com.example.AppKt.main(App.kt:8)

Caused by: java.lang.InstantiationException: Type `kotlin.internal.jdk8.JDK8PlatformImplementations` can not be instantiated reflectively as it does not have a no-parameter constructor or the no-parameter constructor has not been added explicitly to the native image.

at java.lang.Class.newInstance(DynamicHub.java:793)

at kotlin.internal.PlatformImplementationsKt.<clinit>(PlatformImplementations.kt:41)

... 6 more

最小工作示例项目 here

Answer 1

您必须修改reflections rules
将以下内容添加到 native-image 参数:

-H:ReflectionConfigurationFiles=/path/to/reflectconfig

并将受影响的类的规则放入reflectionconfig文件中:

[{
    "name" : "kotlin.internal.jdk8.JDK8PlatformImplementations",
    "allDeclaredConstructors" : true,
    "allPublicConstructors" : true,
    "allDeclaredFields" : true,
    "allPublicFields" : true,
    "allDeclaredMethods" : true,
    "allPublicMethods" : true
}]

或者，您也可以使用相同的文件指定 init 方法， read this