Running jar results in ClassNotFoundException (Gradle)

Question

So I'm relatively inexperienced on how gradle works, and I need some help getting my jar working. My application generates some files through the terminal. However, when I try to run the jar, it gives me an error.

build.gradle:

plugins {
    id 'java'
}

group 'me.tl0x'
version '1.0'

repositories {
    mavenCentral()
}

jar {
    manifest {
        attributes (
                'Main-Class': 'me.tl0x.Main'
        )
    }
}

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'

    implementation 'org.freemarker:freemarker:2.3.29'
    implementation 'com.google.code.gson:gson:2.8.6'
    implementation 'org.jline:jline:3.21.0'
    implementation 'org.fusesource.jansi:jansi:2.4.0'

}

test {
    useJUnitPlatform()
}

Error Message:

PS C:\Path> java -jar ./build/libs/FabricModGenerator-1.0.jar
Exception in thread "main" java.lang.NoClassDefFoundError: org/jline/terminal/TerminalBuilder
        at me.tl0x.terminal.Interface.<init>(Interface.java:29)
        at me.tl0x.Main.main(Main.java:48)
Caused by: java.lang.ClassNotFoundException: org.jline.terminal.TerminalBuilder
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:636)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:182)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519)
        ... 2 more

Any help would be greatly appreciated.

Answer 1

It's basically because your classpath doesn't include "jline" and the other stuffs required by your application.

• Just use the application plugin and let that do the right thing (this is the right answer...)

But if it's a utility thing that you're doing...

• Create a task that does the right thing and just run it via gradle (since you have no arguments)

def asFileUrl(filepath) {
  return "file:///" + new java.net.URI(null, filepath, null).toASCIIString();
}


task LauncherJar(type: Jar) {
    appendix = "launcher"
    ext.launcherClasspath = { ->
      def verifyLibs = [
              configurations.runtimeClasspath.collect { asFileUrl(it.getCanonicalPath()) }.join(' '),
              asFileUrl(jar.archivePath.getCanonicalPath())
              ]
      return verifyLibs.join(' ')
    }
    manifest {
        attributes ("Class-Path": launcherClasspath())
    }
}

task execMyJar(type: JavaExec, dependsOn: [jar, LauncherJar]) {
    group = 'Execution'
    description = 'Do The thing that needs doing'
    classpath = files(LauncherJar.archivePath)
    mainClass = 'me.tl0x.Main'
}

Then you can just do gradle execMyJar.

Note that here, I'm creating a launcher jar with the Class-Path element in the Manifest file. The reason for that is to avoid the situation (Windows only?) where your command line is too long... It might not matter in your case since you haven't got that many dependencies listed (but I don't know about transitive dependencies).