c

build.gradle

@@ -17,8 +17,13 @@ dependencies {
 }
 
 jar {
+    manifest {
+        attributes(
+                "Manifest-Version": 1.0,
+                "Main-Class": "org.example.Main")
+    }
     archiveName = 'app.jar'
-    from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
+    from { configurations.compileClasspath.collect { it.isDirectory() ? it : zipTree(it) } }
     into('assets') {
         from 'assets'
     }

build/tmp/jar/MANIFEST.MF

@@ -0,0 +1,3 @@
+Manifest-Version: 1.0
+Main-Class: org.example.Main
+