Gradle build - add module path

Question

My question: How do I set a module path for gradle build?

I\'ve become comfortable working with Java modules from the command line. I do a frequent exe

Answer 1

Since Gradle 6.4 you can used set the inferModulePath property on the project Java plugin to automatically set the module path:

subprojects {
    plugins.withType(JavaPlugin).configureEach {
        java {
            modularity.inferModulePath = true
            sourceCompatibility = JavaVersion.VERSION_11
            targetCompatibility = JavaVersion.VERSION_11
        }
    }
}

Answer 2

First please note: I am on Gradle 6.6.1 with Java 15.

This is what I have observed:

1. in order to make the compile work, every project needs:

   java {
       modularity.inferModulePath = true
   }
   

2. this can be turned on at root build.gradle via

    subprojects {
        apply plugin: "java"
        java {
            modularity.inferModulePath = true
        }
    }
   

3. in order to use modulepath with gradle run (ServiceLoader working WITHOUT META-INF, reflection restrictions ...) you have to use following application section:

   application {
        mainModule = 'org.gradle.sample.app' // name defined in module-info.java
        mainClass = 'org.gradle.sample.Main'
        // DO NOT USE   mainClassName = 'org.gradle.sample.Main'
   }
   

Took me quite some time to put all together from several Gradle pages --- but it is all here.

Note:

This will not but non-modular jars to the module-path.

Answer 3

I know it can be confusing, but it can definitely be done by gradle. You will need to use a multiproject build to have this work. In your top-most build.gradle, do this:

subprojects {
    apply plugin: 'java'

    sourceCompatibility = 1.9

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

In your settings.gradle:

rootProject.name = 'module-testing'

include 'src:greetMod'
include 'src:appMod'

Everything inside appMod should be moved into a folder called appModSrc. Do the same for greetMod so use greetModSrc.

---

greetMod

Directory structure:

├── build.gradle
└── greetModSrc
    ├── greetPack
    │   └── Hello.java
    └── module-info.java

build.gradle

sourceSets {
    main {
        java {
            srcDirs 'greetModSrc'
        }
    }
}

---

appMod

Directory structure:

├── appModSrc
│   ├── appPack
│   │   └── Entry.java
│   └── module-info.java
└── build.gradle

build.gradle

plugins {
    id 'application'
}

sourceSets {
    main {
        java {
            srcDirs 'appModSrc'
        }
    }
}

application {
    mainClassName 'appPack.Entry'
}

jar {
    doFirst {
        manifest {
            attributes('ModuleMainClass': mainClassName)
        }
    }
}

dependencies {
    implementation project(':src:greetMod')
}

---

With this setup, you can simply run ./gradlew :src:appMod:run:

> Task :src:appMod:run
Greetings from Hello class!

You can download the idea project here: https://github.com/smac89/multi-java9-gradle