Unable to change Main-Class property within Manifest.mf - spring

Question

I am upgrading a springboot app from 1.X to 2.1.3.RELEASE. My Springboot is a multi module project setup which is triggered using a java command something similar to this.
java -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5088 -Drun.jvmArguments="-Xdebug" -Dloader.path=C:\code\build\libs\dir\ -jar C:\code\build/libs/core.jar --spring.config.location=C:\config\application.properties
This is how the project structure looks like
App
Common
Core (has the main class)
Sub
Before the upgrade : Manifest.mf file of core.jar looks like this
Manifest-Version: 3.2.15.signature.LOCALDEV
Project-Name: core
Built-By: dkumar
Built-Date: 2020-11-10 16:09
Project-Version: 3.2.15.signature.LOCALDEV
Spring-Boot-Version: 1.5.1.RELEASE
Main-Class: org.springframework.boot.loader.PropertiesLauncher
Git-Branch: signature
Start-Class: com.demo.Main
Spring-Boot-Classes: BOOT-INF/classes/
Git-Commit-Hash: signature
Project-Group: com.demo.print
Spring-Boot-Lib: BOOT-INF/lib/
After the upgrade. This what the manifest.mf file looks like
Manifest-Version: 3.1.87.upgradespring.LOCALDEV
Git-Branch: upgradespring
Project-Name: core
Built-By: dkumar
Built-Date: 2020-11-18 18:15
Start-Class: com.demo.Main
Git-Commit-Hash: upgradespring
Project-Group: com.demo.print
Project-Version: 3.1.87.upgradespring.LOCALDEV
Main-Class: org.springframework.boot.loader.JarLauncher
Before the upgrade the following property in my Core build.gradle took care of using org.springframework.boot.loader.PropertiesLauncher which inturn used -Dloader.path to load all the Sub (subprojects) jars on to the classpath
springBoot{
mainClass = "com.demo.Main"
layout = "ZIP"
}
After the upgrade, the layout property is now deprecated in 2.1.3.RELEASE and the Main-Class is now changed to Main-Class: org.springframework.boot.loader.JarLauncherand this doesn't support the usage of -Dloader.path (I think). Because of this I always get No bean found error when i try to invoke a class of Sub (subproject). This happens because -Dloader.path fails to include the JARS from subproject onto the classpath. Before the upgrade I could see the relevant jars on the class path.
I tried several ways to change the Main-Class attribute within the manifest to use PropertiesLaucher but none seem to have worked. I have also looked at the plugin documentation and tried something similar but that to didn't work
https://docs.spring.io/spring-boot/docs/2.1.3.RELEASE/gradle-plugin/reference/html/#packaging-executable-configuring-properties-launcher
I think by changing the Main-class I can solve this problem but I am not sure how to do that.
Any suggestions or idea would be helpful. All comments are welcome. I will update the question if the need arises.
I apologize in advance as i am unable to place a larger code snippet due corporate policies.

Answer 1

I was able to resolve this by adding the following properties
bootJar {
manifest {
attributes(
'Main-Class': 'org.springframework.boot.loader.PropertiesLauncher',
'Spring-Boot-Classes': 'BOOT-INF/classes/',
'Spring-Boot-Lib': 'BOOT-INF/lib/'
)
}
}
Only this should work as well within the manifest:
'Main-Class': 'org.springframework.boot.loader.PropertiesLauncher'