How to configure port for a Spring Boot application

As said in docs either set server.port as system property using command line option to jvm -Dserver.port=8090 or add application.properties in /src/main/resources/ with

server.port=8090

For a random port use:

server.port=0

Similarly add application.yml in /src/main/resources/ with:

server:
  port: 8090