Spring Boot YAML: set null property value

Question

I'm having trouble setting null as a property value.

This is how the value is defined in YAML file:

my-property: null

This is how I inject it in code:

@Value("${my-property}")
private String myProperty;

For some reason, Spring keeps injecting an empty string ("") instead of null . Am I missing something or is this an error in Spring?

Answer 1

Try to use instead of $ use this # . Or try this @Value("${<my-property>}")

Answer 2

You can't, but this is not because YAML. YAML supports null as per:

Empty field in yaml

This is because of a Spring processor class, which turns "null" values into empty strings, see here:

https://github.com/spring-projects/spring-framework/issues/19986

Answer 3

I had a similar use case, and had to go through quite a bit of trial and error.

The following two-step solution worked for me

1. Don't define my-property in the YAML file. This way Spring cannot (annoyingly) inject a stringified value like "" or "~" or "null" , and will be forced to look for a default value.

2. Use #{null} as the default value. This is an SpEL expression that evaluates to null .

In your example, it will be

@Value("${my-property:#{null}}")
private String myProperty;

Be careful not to mess up with the curly brackets.