spring boot @Value Could not resolve placeholder

@Configuration
public class PropertySourcePlaceholderConfig {
    @Bean
    public PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer(){
        PropertySourcesPlaceholderConfigurer configurer = new PropertySourcesPlaceholderConfigurer();
        configurer.setIgnoreUnresolvablePlaceholders(true);
        return configurer;
    }

}