Gradle에서 Java 멀티 프로젝트 만들기

단일 프로젝트에서 jar 파일 만들기

gradle 프로젝트 만들기

$ gradle init

Select type of project to generate:
  1: basic
  2: application
  3: library
  4: Gradle plugin
Enter selection (default: basic) [1..4] 1

Select build script DSL:
  1: Groovy
  2: Kotlin
Enter selection (default: Groovy) [1..2] 1

Project name (default: JavaMultiProject): 

> Task :init
Get more help with your project: https://guides.gradle.org/creating-new-gradle-builds

BUILD SUCCESSFUL in 6s
2 actionable tasks: 2 executed

build.gradle 파일 수정

apply plugin: 'java'
apply plugin: 'application'

sourceCompatibility = 11
targetCompatibility = 11

repositories {
    jcenter()
}

dependencies {
}

mainClassName = 'App'
jar {
    manifest {
        attributes 'Main-Class': "App"
    }
}

소스 생성

public class App {
    public static void main(String[] args) {
        System.out.println("Hello");
    }
}

build와 실행을 시도합니다.

$ gradle build

BUILD SUCCESSFUL in 2s
5 actionable tasks: 1 executed, 4 up-to-date

$ java -jar build/libs/JavaMultiProject.jar 
Hello

다중 프로젝트 만들기

.(JavaMultiProject)
├── bar  (アプリケーションプロジェクト)
│   ├── src
│   ├── build.gradle
├── foo  (アプリケーションプロジェクト)
│   ├── src
│   ├── build.gradle
├── share  (共通ライブラリとして利用するプロジェクト)
│   ├── src
│   ├── build.gradle
├── build.gradle
├── setting.gradle

$ mkdir -p bar/src/main/java
$ mkdir -p foo/src/main/java
$ mkdir -p share/src/main/java

setting.gradle 수정

rootProject.name = 'JavaMultiProject'
include 'foo', 'bar', 'share'

build.gradle 수정

allprojects {
}

subprojects {
    apply plugin: 'java'

    sourceCompatibility = 11
    targetCompatibility = 11

    repositories {
        jcenter()
    }
}

apply plugin: 'application'

dependencies {
    implementation project(":share")
}

mainClassName = 'com.example.Bar'
jar {
    manifest {
        attributes 'Main-Class': "com.example.Bar"
    }
    from configurations.compileClasspath.collect { it.isDirectory() ? it : zipTree(it) }
}

$ java -jar bar/build/libs/bar.jar 
Exception in thread "main" java.lang.NoClassDefFoundError: com/example/Hello
    at com.example.Bar.main(Bar.java:5)
Caused by: java.lang.ClassNotFoundException: com.example.Hello
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    ... 1 more

apply plugin: 'application'

dependencies {
    implementation project(":share")
}

mainClassName = 'com.example.Foo'
jar {
    manifest {
        attributes 'Main-Class': "com.example.Foo"
    }
    from configurations.compileClasspath.collect { it.isDirectory() ? it : zipTree(it) }
}

package com.example;

public class Bar {
    public static void main(String[] args) {
        var hello = new Hello("Bar");
        System.out.println(hello.say());
    }
}

package com.example;

public class Foo {
    public static void main(String[] args) {
        var hello = new Hello("Foo");
        System.out.println(hello.say());
    }
}

package com.example;

public class Hello {
    private final String name;
    public Hello(String name) {
        this.name = name;
    }

    public String say() {
        return name + " Hello!";
    }
}

$ gradle :bar:build

BUILD SUCCESSFUL in 804ms
7 actionable tasks: 7 up-to-date

$ ls -l bar/build/libs/
total 8
-rw-r--r--  1 ysaito  staff  1591  4 29 21:15 bar.jar

$ jar xvf bar.jar 
  META-INF/が作成されました
 META-INF/MANIFEST.MFが展開されました
  com/が作成されました
  com/example/が作成されました
 com/example/Bar.classが展開されました
 com/example/Hello.classが展開されました

$ java -jar bar/build/libs/bar.jar 
Bar Hello!
$ java -jar foo/build/libs/foo.jar 
Foo Hello!