Kotlin Gradle build is not running - gradle

Question

I have a Spring Boot application backed with Kotlin as the language, and Gradle as the build system. So basically I'm trying to build a fat jar out of the application source and dependencies, which can be run using Java command line tool.
Gradle build script:
apply plugin: 'java'
apply plugin: 'kotlin'
apply plugin: "kotlin-spring"
apply plugin: 'org.springframework.boot'
group 'myapp'
version '1.0'
buildscript {
ext.kotlin_version = '1.2.21' // Required for Kotlin integration
ext.spring_boot_version = '1.5.4.RELEASE'
repositories {
jcenter()
mavenCentral()
}
dependencies {
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version" // Required for Kotlin integration
classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlin_version" // See https://kotlinlang.org/docs/reference/compiler-plugins.html#kotlin-spring-compiler-plugin
classpath "org.springframework.boot:spring-boot-gradle-plugin:$spring_boot_version"
}
}
sourceSets {
main.java.srcDirs += 'src/main/kotlin/'
test.java.srcDirs += 'src/test/kotlin/'
}
jar {
zip64 true
manifest {
attributes 'Main-Class': 'app.main.ApplicationKt'
}
from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
}
sourceCompatibility = 1.8
repositories {
mavenCentral()
jcenter()
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlin_version"
compile("org.jetbrains.kotlin:kotlin-reflect")
compile group: 'com.typesafe', name: 'config', version: '1.3.2'
compile 'org.springframework.boot:spring-boot-starter-web'
compile group: 'org.apache.camel', name: 'camel-spring-boot-starter', version: '2.20.2'
compile group: 'org.springframework.boot', name: 'spring-boot-starter-data-redis', version: '2.0.0.RELEASE'
compile group: 'org.apache.camel', name: 'camel-quartz2', version: '2.20.2'
compile group: 'org.apache.camel', name: 'camel-http4', version: '2.20.2'
compile group: 'org.apache.camel', name: 'camel-docker', version: '2.20.2'
compile group: 'org.apache.camel', name: 'camel-aws', version: '2.20.2'
compile group: 'com.jayway.jsonpath', name: 'json-path', version: '2.4.0'
compile group: 'redis.clients', name: 'jedis', version: '2.9.0'
compile group: 'joda-time', name: 'joda-time', version: '2.9.9'
compile group: 'net.gpedro.integrations.slack', name: 'slack-webhook', version: '1.4.0'
compile group: 'org.json', name: 'json', version: '20180130'
compile group: 'org.jfree', name: 'jfreechart', version: '1.5.0'
testCompile group: 'junit', name: 'junit', version: '4.12'
}
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
If I run the project using gradle command then it runs fine. But when I build the jar and try ti run it complains with the below error:-
Error: Could not find or load main class app.main.ApplicationKt
Application.kt:-
#SpringBootApplication
#ImportResource("classpath*:camel-context.xml")
#ComponentScan("app")
class Application
fun main(args:Array<String>){
SpringApplication.run(Application::class.java, *args)
}
Not sure where exactly I'm doing anything wrong.

Answer 1

In Application.kt, you do not have a package declaration. From the documentation:
All the contents (such as classes and functions) of the source file are contained by the package declared. So, in the example above, the full name of baz() is foo.bar.baz, and the full name of Goo is foo.bar.Goo.
If the package is not specified, the contents of such a file belong to "default" package that has no name.
You can look into the build/classes directory to inspect what packages the classes were compiled into.
To fix this issue, add package app.main to the top of the Application.kt file.

Answer 2

for some reason I encountered the same error but my package was declared. I copied the package deleted the line and pasted, saved, reloaded the project and the application ran. I don´t have a logical explanation for this, but that is how I solved this error.