spring application.yml reference list from another property

Question

I have property file application-dev.yml with content:

spring.profiles: dev
config.some.value:
- ELEMENT1
- ELEMENT2

and another application-staging.yml with content:

spring.profiles: staging
config.some.value:
- ELEMENT1
- ELEMENT2
- ELEMENT3

so I basically do not know size of list. When I reference this list in main application.yml like this:

some.value: ${config.some.value}

I get Failed to convert property value of type 'java.lang.String' to required type 'java.util.List' for property 'value'. How to reference it correctly?

Chinchilla

so what do you wanna do exactly? you wanna include staging and dev in default application.yml? – Wiley

Answer 1

Solution

One way would be to use comma-separated lists in your profiles:

• application-dev.yml

spring.profiles: dev
config.some.value: ELEMENT1,ELEMENT2

• application-staging.yml

spring.profiles: staging
config.some.value: ELEMENT1,ELEMENT2,ELEMENT3

Then you should be able to access it in application.yml

some.value: ${config.some.value}

This solution doesn't require knowing list size upfront.

Explanation

The reason why this is working is described here. Specifically:

YAML lists are represented as comma-separated values (useful for simple String values) and also as property keys with [index] dereferencers, for example this YAML:
servers:
    - dev.bar.com
    - foo.bar.com
Would be transformed into these properties:
servers=dev.bar.com,foo.bar.com
servers[0]=dev.bar.com
servers[1]=foo.bar.com

In particular this means, that if you specify comma-separated list of strings in application.yml and define List<String> as value in @ConfigurationProperties, spring configuration properties binder will convert that comma-separated list of string to List<Strings>.

Fishtail

Answer 2

MyProfile:
SomeValues: 
    - ELEMENT1
    - ELEMENT2
     -ELEMENT3
    - ELEMENT4

---
MyProfile:   
someValues: 
    - ELEMENT1
    - ELEMENT2



@Configuration
@EnableConfigurationProperties
@ConfigurationProperties
public class YAMLConfig {


    private List<String> SomeValues= new ArrayList<>();

    // standard getters and setters

}

To Access properties

  @Autowired
   private YAMLConfig myConfig;


 private List<String> SomeValues= myConfig.SomeValues();

This worked for me

Cordate

I cannot change code. I need to do it only in .yml files. – Chinchilla

Answer 3

When using String arrays the first and only element CAN be joined by commas - the final result is the same as a list. Meaning that you can set your variable like this:

config.some.value: ELEMENT1, ELEMENT2, ELEMENT3

then, at your profile section, you can reference the configuration value as it were a normal string:

someValues: ${config.some.value}

Constitutional

Answer 4

This is the best way to create .yml file with multiple values:

spring:
  profiles: dev
  config:
    some:
      values: ELEMENT1,ELEMENT2

When we are using .yml files, we recommend pulling apart each word. To read values use:

@Value("${spring.config.some.values}")    
private String[] values;

I hope it helps you.

Lituus