1、根項目gradle.properties

org.gradle.jvmargs=-Xmx256m -XX:MetaspaceSize=256m -XX:+HeapDumpOnOutOfMemoryError 

systemProp.SERVICE_NAMESPACE=myns

2、build.gradle

run {
    systemProperties System.getProperties()
}

3、java

public class TestApplication {
    public static void main(String[] args) {
        System.out.println(System.getProperty("SERVICE_NAMESPACE"));
        SpringApplication.run(TestApplication.class, args);
    }
}

完成。