1. SpringBoot version: 2.5.0

2.Environment Variable Prefixes

https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.5-Release-Notes#environment-variable-prefixes

3.

@SpringBootApplication
public class MyApp {

    public static void main(String[] args) {
        SpringApplication application = new SpringApplication(MyApp.class);
        application.setEnvironmentPrefix("myapp");
        application.run(args);
    }
}

4.the application.properties

myapp.server.port=8000
  1. but the server port is 8080(default) or not 8000(myapp.server.port)
021-05-22 21:33:44.323  INFO 9759 --- [           main] noxus.com.draven.prefix.MyApp            : Starting MyApp using Java 1.8.0_231 on draven with PID 9759 (/Users/draven/Documents/documents/java/documents/draven-springboot/noxus-draven-springboot-2.5.x/noxus-draven-2.5.x-prefix/target/classes started by draven in /Users/draven/Documents/documents/java/documents/draven-springboot)
2021-05-22 21:33:44.326  INFO 9759 --- [           main] noxus.com.draven.prefix.MyApp            : No active profile set, falling back to default profiles: default
2021-05-22 21:33:44.936  INFO 9759 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-05-22 21:33:44.943  INFO 9759 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-05-22 21:33:44.943  INFO 9759 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.46]
2021-05-22 21:33:44.991  INFO 9759 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-05-22 21:33:44.991  INFO 9759 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 632 ms
2021-05-22 21:33:45.243  INFO 9759 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2021-05-22 21:33:45.251  INFO 9759 --- [           main] noxus.com.draven.prefix.MyApp            : Started MyApp in 5.137 seconds (JVM running for 38.743)
2021-05-22 21:33:45.252  INFO 9759 --- [           main] o.s.b.a.ApplicationAvailabilityBean      : Application availability state LivenessState changed to CORRECT

Comment From: snicoll

@maoxiaoxiong adding a property in application.properties does not constitute a system environment variables. This feature is limited to those as the focus is to be used when several Spring Boot apps are running in the same OS environment.