Here are 4 ways to do this. Note that the first 3 methods modify the existing Jar task of Gradle.
Method 1: Placing library files beside the result JAR
This method does not need application or any other plugins.
tasks.jar {
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
manifest.attributes["Class-Path"] = configurations
.runtimeClasspath
.get()
.joinToString(separator = " ") { file ->
"libs/${file.name}"
}
}
Note that Java requires us to use relative URLs for the Class-Path attribute. So, we cannot use the absolute path of Gradle dependencies (which is also prone to being changed and not available on other systems). If you want to use absolute paths, maybe this workaround will work.
Create the JAR with the following command:
./gradlew jar
The result JAR will be created in build/libs/ directory by default.
After creating your JAR, copy your library JARs in libs/ sub-directory of where you put your result JAR. Make sure your library JAR files do not contain space in their file name (their file name should match the one specified by ${file.name} variable above in the task).
Method 2: Embedding the libraries in the result JAR file (fat or uber JAR)
This method too does not need any Gradle plugin.
tasks.jar {
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
val dependencies = configurations
.runtimeClasspath
.get()
.map(::zipTree) // OR .map { zipTree(it) }
from(dependencies)
duplicatesStrategy = DuplicatesStrategy.EXCLUDE
}
Creating the JAR is exactly the same as the previous method.
Method 3: Using the Shadow plugin (to create a fat or uber JAR)
plugins {
id("com.github.johnrengelman.shadow") version "6.0.0"
}
// Shadow task depends on Jar task, so these configs are reflected for Shadow as well
tasks.jar {
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
}
Create the JAR with this command:
./gradlew shadowJar
See Shadow documentations for more information about configuring the plugin.
Method 4: Creating a new task (instead of modifying the Jar task)
tasks.create("MyFatJar", Jar::class) {
group = "my tasks" // OR, for example, "build"
description = "Creates a self-contained fat JAR of the application that can be run."
manifest.attributes["Main-Class"] = "com.example.MyMainClass"
duplicatesStrategy = DuplicatesStrategy.EXCLUDE
val dependencies = configurations
.runtimeClasspath
.get()
.map(::zipTree)
from(dependencies)
with(tasks.jar.get())
}
Running the created JAR
java -jar my-artifact.jar
The above solutions were tested with:
- Java 17
- Gradle 7.1 (which uses Kotlin 1.4.31 for .kts build scripts)
See the official Gradle documentation for creating uber (fat) JARs.
For more info about manifests, see Oracle Java Documentation: Working with Manifest files.
For difference between tasks.create() and tasks.register() see this post.
Your resource files will be included in the JAR file automatically (assuming they were placed in classpath: /src/main/resources/ directory or any custom directory set as resources root in the build file). Here is how to access a resource file in your code (note the / at the start of names):
- Kotlin
val vegetables = MyClass::class.java.getResource("/vegetables.txt").readText()
// Alternative ways:
// val vegetables = object{}.javaClass.getResource("/vegetables.txt").readText()
// val vegetables = MyClass::class.java.getResourceAsStream("/vegetables.txt").reader().readText()
// val vegetables = object{}.javaClass.getResourceAsStream("/vegetables.txt").reader().readText()
- Java
var stream = MyClass.class.getResource("/vegetables.txt").openStream();
// OR var stream = MyClass.class.getResourceAsStream("/vegetables.txt");
var reader = new BufferedReader(new InputStreamReader(stream));
var vegetables = reader.lines().collect(Collectors.joining("\n"));
