How to concat strings in application.yaml?

Question

I want to add two lines in a yaml file, or rather, I want the instance-id field to contain the result of adding the values of the port and name fields I tried using +, tried through various tags that I saw in similar questions, like !join, !concat (java says they don't exist). But nothing worked in the end. Is there a solution?

Example yaml (Sorry, i dont know how to load yaml here):

server:
  port: &port 62000
spring:
  application:
    name: &appname 'appname'
eureka:
  client:
    service-url:
      defaultZone: 'http://localhost:8081/eureka/'
  instance:
    instance-id: here should be *appname + ":" + *port (result appname:62000)

Answer 1

This won't work for YAML in general, but it will work in Spring Boot, since you can use Property Placeholders, and thus reference other properties from within a property value:

server:
  port: 62000
spring:
  application:
    name: 'appname'
eureka:
  client:
    service-url:
      defaultZone: 'http://localhost:8081/eureka/'
  instance:
    instance-id: ${spring.application.name}:${server.port}

This also works with environment variables, btw.