Gradle多根多模块项目构建问题：Jar无法运行及IntelliJ运行异常

Hey there! Let's tackle your problems one by one—getting those component Jars to run properly and fixing the IntelliJ execution quirks.

1. Align Project Structure with settings.gradle #

Your current settings.gradle doesn't match your actual project directory hierarchy, which is likely causing hidden dependency resolution issues. Update it to reflect the components/ and modules/ folder structure:

// settings.gradle
rootProject.name = 'gradle_root_project'
// Include components with their correct directory paths
include 'components:software_component_a', 'components:software_component_b'
// Include modules under the modules folder
include 'modules:module_a', 'modules:module_b', 'modules:module_c', 'modules:module_d'

This ensures Gradle recognizes all subprojects correctly, so your component projects can reference modules without path errors.

2. Fix Component Dependency References #

Update your software component's build.gradle to use the corrected project paths from the updated settings.gradle:

// components/software_component_a/build.gradle
plugins {
    id 'java'
    id 'application'
    id 'io.freefair.lombok' version '4.1.1'
}

application {
    mainClassName = 'io.cloudsystem.Controller' // Double-check this class has a valid main() method!
}

dependencies {
    // Match project paths to what's defined in settings.gradle
    implementation project(':modules:module_a')
    implementation project(':modules:module_b')
    implementation project(':modules:module_c')
    // Add module_d if your component depends on it
}

3. Generate Runnable Fat Jars #

The default jar task only packages your component's code, not its dependencies—this is why your current Jar won't run. Use one of these methods to create a self-contained runnable Jar:

Option A: Use the Shadow Plugin (Simpler) #

Add the Shadow plugin to your component's build.gradle to automatically build a "fat jar" with all dependencies included:

plugins {
    // ... existing plugins ...
    id 'io.freefair.shadow' version '8.1.0' // Pick a version compatible with your Gradle setup
}

shadowJar {
    mergeServiceFiles()
    manifest {
        attributes 'Main-Class': 'io.cloudsystem.Controller'
    }
}

Build the runnable Jar with:

gradle :components:software_component_a:shadowJar

The Jar will be located at components/software_component_a/build/libs/software_component_a-2.0.0-all.jar (the -all suffix marks it as a fat jar).

Option B: Manual Fat Jar Task #

If you prefer avoiding extra plugins, define a custom fatJar task in your component's build.gradle:

task fatJar(type: Jar) {
    manifest {
        attributes 'Main-Class': 'io.cloudsystem.Controller'
    }
    // Include all runtime dependencies
    from { configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) } }
    // Include your component's compiled code
    with jar
}

Build it with:

gradle :components:software_component_a:fatJar

The Jar will be in components/software_component_a/build/libs/software_component_a-2.0.0.jar.

4. Fix IntelliJ Execution Problems #

• Refresh Gradle Configuration: In IntelliJ, open the Gradle panel (right sidebar), click the refresh icon ("Reload All Gradle Projects") to ensure the IDE picks up your updated settings.
• Run the Component Directly: Instead of running the root project, find your component's run task in the Gradle panel: gradle_root_project > components > software_component_a > Tasks > application > run. Right-click and select "Run"—this will execute your component with all dependencies loaded properly.
• Validate Main Class: Confirm io.cloudsystem.Controller has a valid public static void main(String[] args) method—this is required for the application plugin to launch your code.

5. Clean Up Root Project Config #

Move the test and JavaCompile settings into the subprojects block in your root build.gradle so all subprojects inherit them (right now they only apply to the root project):

// root build.gradle
plugins {
    id 'java'
    id 'io.freefair.lombok' version '4.1.1'
}

subprojects {
    apply plugin: 'java'
    apply plugin: 'io.freefair.lombok'
    sourceCompatibility = '1.8'
    group = 'io.cloudsystem'
    version = '2.0.0'
    compileJava.options.encoding = 'UTF-8'
    compileTestJava.options.encoding = 'UTF-8'
    javadoc.options.encoding = 'UTF-8'
    repositories {
        mavenCentral()
    }
    dependencies {
        testImplementation 'org.junit.jupiter:junit-jupiter-api:5.5.2'
        testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.5.2'
    }
    // Apply JUnit Platform to all subproject tests
    test {
        useJUnitPlatform()
    }
    // Enforce UTF-8 encoding for all subproject Java compiles
    tasks.withType(JavaCompile) {
        options.encoding = 'UTF-8'
    }
}

After making these changes, run gradle clean build to rebuild everything from scratch, then test the runnable Jar and IntelliJ execution again.

内容的提问来源于stack exchange，提问作者Felix Gaebler