What does @ConfigurationProperties do, and how is it different from @Value?

@ConfigurationProperties binds an entire group of related, hierarchical configuration properties (e.g. everything under app.mail.*) into a single strongly-typed POJO with matching fields, all at once, with built-in validation support. @Value injects one individual property at a time into one field — @ConfigurationProperties is the better choice once you have more than a couple of related settings, since it avoids a long list of scattered @Value fields.