How to use @ConfigurationProperties annotation in Spring Boot

Question

I am trying to apply @ConfigurationProperties annotation to get a map from application.yml file to places in code where I need it.

Here is the code I have so far:

application.yml

repository:
    type:
      big: big
      small: small
      medium: medium
    to:
     database:
      something: "STRING"

configuration.java

@Configuration
@EnableConfigurationProperties
public class SnowflakeRepositoryConfig {

        @Bean
        @ConfigurationProperties(prefix = "repository.type")
        public DatabaseTypeMapping databaseTypeMapping() {
            return new DatabaseTypeMapping();
        }
    
        public static class DatabaseTypeMapping {
            public Map<Type, Type> typeMappingMigration;
    
            public void setMapping(Map<Type, Type> typeMappingMigration) {
                this.typeMappingMigration = typeMappingMigration; }
        }

@Bean
@ConfigurationProperties(prefix = "repository.to.database")
public BrandToDatabaseProperties brandToDatabaseProperties() {
    return new BrandToDatabaseProperties();
}

public static class BrandToDatabaseProperties {
    public Map<Brand, String> mapping;

    public void setMapping(Map<Brand, String> mapping) {
        this.mapping = mapping;
    }
}

And in config file I am applying it to serviceImpl class like this:

    @Bean
    public UserDataService getUserData(BrandToDatabaseProperties brandToDatabaseProperties, DatabaseTypeMapping databaseTypeMapping){
       return new UserDataServiceImpl(brandToDatabaseProperties.mapping, databaseTypeMapping.typeMappingMigration);
    }

In serviceImpl.java class, I include it like this:

    public class UserDataServiceImpl implements UserDataService {
    
        private final Map<Type, Type> typeMappingMigration;
        private final Map<Brand, String> brandToDatabaseMapping;
    
        public UserDataServiceImpl(Map<Brand, String> brandToDatabaseMapping, Map<Type, Type> typeMappingMigration) {
this.brandToDatabaseMapping = Collections.unmodifiableMap(brandToDatabaseMapping);    
            this.typeMappingMigration = Collections.unmodifiableMap(typeMappingMigration);    
        }

When I try to start my application, I am getting the following error:

Failed to instantiate [service.UserDataService]: Factory method 'getUserData' threw exception; nested exception is java.lang.NullPointerException

What am I missing here?

Answer 1

You don't need to declare a bean of type DatabaseTypeMapping . Move the ConfigurationProperties annotation to the class, and let component scan pick it up. Alternatively, you can specify the class name in the EnableConfigurationProperties annotation.

I can't be sure but I think ConfigurationProperties isn't supposed to be declared on a method, it doesn't make sense logically.