# application.yml
app:
  name: MySpringBootApp
  version: 1.0.0

@Component
public class AppConfig {
    @Value("${app.name}")
    private String appName;
    @Value("${app.version}")
    private String version;
}

# application.yml
database:
  host: 192.168.1.100
  port: 3307
  username: admin
  password: secret123

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties(prefix = "database") // 對(duì)應(yīng) yml 中 database 開(kāi)頭的配置
public class DatabaseConfig {
    private String host = "localhost";
    private int port = 3306;
    private String username;
    private String password;

    // 必須有 getter/setter（或用 Lombok @Data）
    public String getHost() { return host; }
    public void setHost(String host) { this.host = host; }
    public int getPort() { return port; }
    public void setPort(int port) { this.port = port; }
    // ... 其他 setter/getter
}

@Service
public class UserService {
    private final DatabaseConfig dbConfig;

    public UserService(DatabaseConfig dbConfig) {
        this.dbConfig = dbConfig;
    }

    public void connect() {
        System.out.println("連接數(shù)據(jù)庫(kù): " + dbConfig.getHost() + ":" + dbConfig.getPort());
    }
}

# application.yml
app:
  security:
    jwt:
      secret: mySecretKey
      expire-hours: 24
    cors:
      allowed-origins:
        - http://localhost:3000
        - https://myapp.com

@Component
@ConfigurationProperties(prefix = "app")
public class AppProperties {
    private Security security = new Security();

    public static class Security {
        private Jwt jwt = new Jwt();
        private Cors cors = new Cors();

        public static class Jwt {
            private String secret;
            private int expireHours;
            // getters/setters
        }

        public static class Cors {
            private List<String> allowedOrigins = new ArrayList<>();
            // getter/setter
        }
        // getters/setters
    }
    // getter for security
}

@Component
@ConfigurationProperties(prefix = "xxx")
public class XxxProperties { ... }

@Configuration
@EnableConfigurationProperties({DatabaseConfig.class, AppProperties.class})
public class AppConfig { }