找不到gradle拼图模块

问题描述

我尝试运行一个使用Java 9模块的非常简单的gradle项目，但收到以下错误.

I try to run a very simple gradle project which uses java 9 modules, but i receive the following error.

/home/vadim/IdeaProjects/test_modules/src/main/java/module-info.java:2: error: module not found: HdrHistogram
    requires HdrHistogram;
             ^

这里是 https://github.com/vad0/test_modules .主类基本上什么都不做.

Here is it https://github.com/vad0/test_modules.The main class does basically nothing.

package app;

import org.HdrHistogram.Histogram;

public class RunHdr {
    public static void main(String[] args) {
        final Histogram histogram = new Histogram(5);
        System.out.println(histogram);
    }
}

它仅使用一种依赖性:HdrHistogram.根据官方gradle教程 https://docs，我在build.gradle中包含了此魔术命令. gradle.org/current/samples/sample_java_modules_multi_project.html .

It uses only one dependency: HdrHistogram. I included this magic command in build.gradle according to official gradle tutorial https://docs.gradle.org/current/samples/sample_java_modules_multi_project.html.

java {
    modularity.inferModulePath = true
}

整个build.gradle看起来像这样.

The whole build.gradle looks like this.

plugins {
    id 'java'
}

group 'org.example'
version '1.0-SNAPSHOT'

repositories {
    mavenCentral()
}

java {
    modularity.inferModulePath = true
}

dependencies {
    compile group: 'org.hdrhistogram', name: 'HdrHistogram', version: '2.1.12'
    testCompile group: 'junit', name: 'junit', version: '4.12'
}

module.info看起来像这样

module.info looks like this

module test.modules.main {
    requires HdrHistogram;
}

我已经阅读了许多有关Jigsaw的教程以及与之相关的一大堆stackoverflow问题，但是仍然无法使这个简单的示例生效.我该如何解决?

I have already read a number of tutorials on Jigsaw and a whole bunch of stackoverflow questions related to it, but still can't make this simple example work. How do i fix it?

谢谢

推荐答案

不幸的是，gradle并未将每个jar都视为一个模块(简单来说).如果要了解确切是如何gradle构建module-path(而不是class-path)的，则可能要从此处，特别是在 isModuleJar 方法.很容易理解(尽管花了我近两天的时间来设置gradle和调试问题)，您要使用的依赖项:gradle表示它不是模块(没错，但是我也不知道它是正确的).要使其非常正确，请gradle 会将您的依赖项添加到CLASSPATH ，但在下一行:它将 not 将您的依赖项添加到module-path，因为如果isModuleJar中的过滤器失败.

Unfortunately, gradle does not treat every jar as a module (in simple words). If you want to find out how exactly is gradle building the module-path (as opposed to class-path), you probably want to start from here, specifically at the isModuleJar method. It's pretty easy to understand (though it took me almost two days to set-up gradle and debug the problem out) that the dependency that you are trying to use : gradle says that it is not a module (it isn't wrong, but I am not sure it is correct either). To make it very correct, gradle will add your dependency to the CLASSPATH, but in the very next line: it will not add your dependency to the module-path, because if fails the filter in isModuleJar.

我不知道这是否是错误，或者是否是故意的，但是解决方案很简单:

I do not know if this is a bug or not, or may be this is on purpose, but the solution is easy:

plugins.withType(JavaPlugin).configureEach {
   java {
       modularity.inferModulePath = true
   }

   tasks.withType(JavaCompile) {
      doFirst {
          options.compilerArgs = [
                 '--module-path', classpath.asPath,
          ]
          classpath = files()
    }
}

您将其故意添加到路径中.我将其标记为缺陷，让我们看看他们怎么说.

you add it to the path, on purpose. I will flag this as a defect and let's see what they have to say.

编辑

更好的是，使用由gradle提交者编写的插件:

Even better, use a plugin that is written by a gradle commiter:

plugins {
    id 'java'
    id 'de.jjohannes.extra-java-module-info' version "0.1"
}

最简单的选择是:

extraJavaModuleInfo {
     automaticModule("HdrHistogram-2.1.12.jar", "HdrHistogram")
}

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