解读@ConfigurationProperties和@value的区别

  // 配置类定义
  @Component
  @ConfigurationProperties(prefix = "app.datasource")
  public class DataSourceConfig {
      private String url;
      private String username;
      private int maxPoolSize;
      // Getters and Setters
  }
  
// 业务类调用
@Service
public class DataSourceService {
    @Autowired
    private DataSourceConfig dataConfig; // 直接注入配置对象

    public void connect() {
        System.out.println("Connecting to: " + dataConfig.getUrl() + ":" + dataConfig.getUsername());
    }
}

 # application.properties
 app.datasource.url=jdbc:mysql://localhost:3306/db
 app.datasource.username=power
 app.datasource.max-pool-size=10

app:
  datasource:
    url: jdbc:mysql://localhost:3306/db
    username: power
   maxPoolSize: 10

/ 配置类定义（无需 @Component）
@ConfigurationProperties(prefix = "app.mail")
public class MailConfig {
    private String host;
    private int port;
    // getter/setter
}

// 主启动类显式启用
@SpringBootApplication
@EnableConfigurationProperties(MailConfig.class)
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

// 业务类调用（构造器注入）
@Service
public class MailService {
    private final MailConfig mailConfig;

    public MailService(MailConfig mailConfig) {
        this.mailConfig = mailConfig;
    }
}

@Component
public class MyService {
    @Value("${app.feature.enabled:false}")
    private boolean featureEnabled;

    @Value("#{systemProperties['user.timezone']}")
    private String timezone;
}

app:
  servers:
    - name: server1
      ip: 192.168.1.1
    - name: server2
      ip: 192.168.1.2

@ConfigurationProperties(prefix = "app")
public class AppConfig {
    private List<Server> servers;
    // Getters and Setters
}

@Value("${app.servers[0].name}")
private String server1Name;

@ConfigurationProperties(prefix = "app")
@Validated
public class AppConfig {
    @NotNull
    private String name;
    @Min(1)
    private int maxConnections;
}

@Value("${app.name:DefaultApp}")
private String appName;