Binding external configurations to POJO classes

package com.sanhaoxuesheng.demo.config;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.convert.DurationUnit;

import lombok.Data;

import java.time.Duration;
import java.time.temporal.ChronoUnit;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Data
@ConfigurationProperties(prefix = "app")
public class AppProperties {
    private String name;
    private String description;
    private String uploadDir;
    private Duration connectTimeout = Duration.ofMillis(1000);
    @DurationUnit(ChronoUnit.SECONDS)
    private Duration readTimeout = Duration.ofSeconds(30);
    private final Security security = new Security();

    @Data
    public static class Security {
        private String username;
        private String password;
        private List<String> roles = new ArrayList<>();
        private boolean enabled;
        private Map<String, String> permissions = new HashMap<>();
    }
}

@SpringBootApplication
@EnableConfigurationProperties(AppProperties.class)
public class DemoApplication {

	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}

}

@Autowired
   AppProperties appProperties;
   
   @GetMapping("/hello")
   public String hello() {

       System.out.println(appProperties);
       return "hello world";
   }