"No main manifest attribute" when creating Kotlin jar using IntelliJ IDEA

When creating a jar from my Kotlin code and running it, it says "No main manifest attribute".
When looking at the manifest.mf, it has this content:

Manifest-Version: 1.0

When looking at the file in the source, it has this content:

Manifest-Version: 1.0
Main-Class: MyMainClass

When manually copying the source manifest to the jar, it runs perfectly.

[Screenshot of my artifact settings][1]



[1]:

If any of the dependent jars has a `MANIFEST.MF` file, it will override your custom one which defines the `Main-Class`.

In order to address this problem you should do the following:

- Disable the [alphabetical ordering](

)
- [Change items ordering](

) so that item which has `META-INF/MANIFEST.MF` file is the first in the list
- Your custom `MANIFEST.MF` will be picked up by IntelliJ IDEA and [displayed for the jar](

) artifact.

See the [related issue](

[To see links please register here]

) for more details.

You can also use Gradle or Maven to generate the fat jar instead.

I got this error with Gradle and Kotlin.
I had to add in my `build.gradle.kts` an explicit manifest attribute:

```
tasks.withType<Jar> {
manifest {
attributes["Main-Class"] = "com.example.MainKt"
}
}
```

From the [gradle documentation][1], it's better to create a fatJar task to englobe all of the runtime dependencies in case you encounter `java.lang.NoClassDefFoundError` errors

[1]:

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1.Add the following task definition in the build script

tasks.jar {
manifest {
attributes["Main-Class"] = "MainKt"
}
configurations["compileClasspath"].forEach { file: File ->
from(zipTree(file.absoluteFile))
}
}

2. Then the jar tasks (Tasks | build | jar) again from the right hand sidebar.

**For Spring boot apps:**

What worked for me (gradle kotlin) in build.gradle.kts

1) add spring boots plugin &. apply dependency management

```
plugins {
id("org.springframework.boot") version "2.6.7"
}
apply(plugin = "io.spring.dependency-management")
```

2) set your main class
```
springBoot {
mainClass.set("com.example.Application")
}
```

Found this all by reading up on spring-boot docs found [here](

[To see links please register here]

)

So far the simplest and best solution I've found is using [Ktor Gradle Plugin][1]

plugins {
id("io.ktor.plugin") version "2.2.3" // Check if it's latest
}

application {
mainClass.set("com.example.ApplicationKt")
}

ktor {
fatJar {
archiveFileName.set("fat.jar")
}
}

Run it with ./gradlew buildFatJar


[1]:

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