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intermittent "No main class is found." errors from the Spring Boot Dashboard in visual studio code

November 30, 2022

I’m just getting started with Java and I prefer Visual Studio Code over Eclipse. I downloaded the popular Java extensions for it including the Spring Boot tools (including Dashboard). When I switch to the Spring Boot Dashboard and click the Run or Debug button, I sometimes get a "No main class is found." popup error message and nothing starts. If I restart vscode, sometimes it works with the project that previously didn’t, but another project that worked in the past is now throwing this error. It doesn’t always happen with the same project. It all seems very random about when this exception is thrown. I have about 6 microservices projects (Eureka discovery, gateway, config server, different business logic), and it’s hard to get all 6 to start. I can reliably start them with the default Run and Debug option or via jars – and they all always work.

All the projects were created with Spring Initializr and they do indeed have a main function:

package ...;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class ...ApiGatewayApplication {

        public static void main(String[] args) {
               SpringApplication.run(...ApiGatewayApplication.class, args);
        }
}