Shadow jar 缺少常见的 Java 类

Question

I'm packaging a shadow jar of my app. The app uses kotlin and some external dependencies. All dependencies are in my jar but i get the following exception during runtime:

java.lang.NoSuchMethodError: java.util.Optional.isEmpty()Z

The Z at the end is always there; I don't where it comes from.

I checked multiple example of build.gradle files and mine seems to be good.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.github.jengelman.gradle.plugins:shadow:6.1.0'
    }
}

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.3.72'
    id 'com.github.johnrengelman.shadow' version '6.1.0'
}

group 'com.bancarelvalentin'
apply plugin: 'com.github.johnrengelman.shadow'
apply plugin: 'kotlin'
apply plugin: 'java'


repositories {
    mavenCentral()
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib"
    implementation "com.discord4j:discord4j-core:3.1.0"
    implementation "com.natpryce:konfig:1.6.10.0"
    implementation "org.json:json:20200518"
    implementation "ch.qos.logback:logback-classic:1.2.3"
    implementation "org.slf4j:slf4j-api:1.7.30"

}

shadowJar {
    archiveBaseName.set('DreamBot')
    archiveClassifier.set('')
    archiveVersion.set('0.0.0')
    mergeServiceFiles()
    manifest {
        attributes 'Main-Class': 'com.bancarelvalentin.dreambot.Main'
    }
}

I have trouble identifying the exact problem is it my java install that is not working properly or is it my jar missing stuff ?

Thanks for your help !

Answer 1

Your runtime Java Version is lower than the compile-time Java version

Optional.isEmpty() is from JDK 11+, its not in JDK 8,9

the build.gradle is fine.

just run with JDK 11