How to define null object value for key-value pair in yaml in Spring Boot?

Question

This is how my configuration looks now:

• this is a key-value = map configuration
• key is a number as an ID
• value is an object as a person
• for the 3rd and 4th I wanted to setup null as person object

setup:
    identifications:
        1:
            name: John
            age: 50
        2:
            name: Sarah
            agen: 40
        3: null
        4:
        5:
            name: Joe
            age: 20

These are the java classes:

@Component
@ConfigurationProperties(prefix = "setup")
public class Setup {

    private Map<Integer, Person> identifications;
    
    getter/setter
    
    public static class Person {
    
        private String name;
        private Integer age;
        
        getters/setters
    
    }

}

After starting spring boot application, I get the following exception:

Caused by: org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [java.lang.String] to type [my.package.Setup.Person]

If I delete the 3rd and 4th (the null ones), the application starts successfully. So it has a problem to insert a key into the map with null value. Is it possible somehow? I know that maps can have null values. But I don't know how to specify null object as a value in yml.

Answer 1

• I assume, you don't want to leave those 2 keys all together from yaml for documentation purposes or something because leaving them have the same effect on the created map

• See this issue. Springs YamlProcessor translates null and empty to "" . https://github.com/spring-projects/spring-boot/issues/8873

• If you define a static method like this in person, it will work

    public static Person of(String value) {
      if (value.trim().isEmpty())
        return null;
      throw new IllegalArgumentException();
    }