使用Gradle构建Kotlin + Java 9项目

问题描述

我对Gradle（和Java 9，说实话）相当新，我正在尝试使用Gradle构建一个简单的库项目，它是Java 9和Kotlin的混合体。更详细地说，Java中有一个接口，Kotlin中有一个实现;我会在Kotlin做一切，但 modules-info.java 无论如何都是java，所以我决定这样做。

I'm fairly new to Gradle (and Java 9, to be honest), and I'm trying to use Gradle to build a simple library project that is a mix of Java 9 and Kotlin. More in detail, there is an interface in Java and an implementation in Kotlin; I'd do everything in Kotlin, but the modules-info.java is java anyway, so I decided to do things this way.

我在IntelliJ Idea上构建，外部定义了1.2.0 kotlin插件和gradle 4.3.1。

I'm building on IntelliJ Idea, with the 1.2.0 kotlin plugin and gradle 4.3.1 defined externally.

文件系统架构是：

+ src
  + main
    + java
      + some.package
        - Roundabout.java [an interface]
      - module-info.java
    + kotlin
      + some.package.impl
        - RoundaboutImpl.kt [implementing the interface]

module-info.java 是：

module some.package {
  requires kotlin.stdlib;
  exports some.package;
}

和 build.gradle 是：

buildscript {
    ext.kotlin_version = '1.2.0'

    repositories {
        mavenCentral()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

group 'some.package'
version '1.0-PRE_ALPHA'

apply plugin: 'java-library'
apply plugin: 'kotlin'

tasks.withType(JavaCompile) {
    options.encoding = 'UTF-8'
}

sourceCompatibility = 9

compileJava {
    dependsOn(':compileKotlin')
    doFirst {
        options.compilerArgs = [
                '--module-path', classpath.asPath,
        ]
        classpath = files()
    }
}

repositories {
    mavenCentral()
}

dependencies {
    compile group: 'org.jetbrains.kotlin', name: 'kotlin-stdlib', version: "$kotlin_version"
    testCompile group: 'junit', name: 'junit', version: '4.12'
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

请注意，我必须在java编译任务中指定模块路径，否则编译将失败：

Notice that I had to specify a module path on the java compile task, or the compilation fails with:

无论如何，现在这个构建失败并出现此错误，我无法弄清楚如何解决它：

Anyway, now this build fails with this error, and I can't figure out how to solve it:

import some.package.impl.RoundaboutImpl;

import some.package.impl.RoundaboutImpl;

错误：找不到符号

返回新的RoundaboutImpl<>（queueSize，parallelism，worker，threadPool）;

return new RoundaboutImpl<>(queueSize, parallelism, worker, threadPool);

我认为编译的Kotlin部分正常，然后java部分失败，因为它没有看到kotlin方面，可以这么说。

I think that the Kotlin part of the compilation is going ok, then the java part fails because it doesn't "see" the kotlin side, so to speak.

我想我应该以某种方式告诉它在类路径中加载已编译的kotlin类;但是（首先）我如何在gradle中做到这一点？和（第二）甚至可能？我认为你不能在Java 9中混合模块路径和类路径。

I think I should tell it somehow to to load the already compiled kotlin classes in the classpath; but (first) how do I do this in gradle? and (second) is it even possible? I think you can't mix module path and class path in Java 9.

我该如何解决这个问题？我认为这是一种非常常见的情况，因为每个java9风格的模块都是混合语言模块（因为 module-info.java ），所以我想我我在这里遗漏了一些非常基本的东西。

How can I solve this? I think it is a pretty common situation, as every java9-style module will be a mixed-language module (because of module-info.java), so I think I'm missing something really basic here.

提前致谢！

推荐答案

解决了！将kotlin编译目录设置为与Java相同的目录就足够了：

Solved! It was sufficient to set the kotlin compilation dir to the same dir as Java:

compileKotlin.destinationDir = compileJava.destinationDir

现在可以使用同一棵树或不同树木中的来源;但有一个怪癖： jar 任务会生成一个包含所有条目重复的jar。我将继续努力解决这个问题。

It works now, both with the sources in the same tree or in different trees; but with a quirk: the jar task produces a jar with all the entries duplicated. I'll work on fix this, next.

感谢所有人！

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