@Import

@Import([...]) adds beans that the component scan does not find: configuration classes from elsewhere, or code that registers beans.

Why

@ComponentScan finds the beans in one directory and below. Use @Import on a configuration class when you need something else:

• a configuration or component class outside the scanned directories (shared code, a legacy module);
• a BeanRegistrar, which registers beans in code;
• an ImportSelector, which returns more BeanModules to load, chosen at startup;
• an ImportBeanDefinitionRegistrar, which registers full bean definitions.

The generator creates registrars and selectors with their no-argument constructor.

Imports share the importing class's conditions. If the importing class is skipped (by @Profile or a condition), what it imports is skipped too.

Example

import 'package:spring_core_dart/spring_core_dart.dart';
// Declared in another package, outside the scanned directory.
import 'package:legacy_billing/legacy_billing.dart' show LegacyBillingConfig;

class Mailer {
  Mailer(this.host);
  final String host;
}

// Registers a mailer only when a mail host is configured.
class MailRegistrar implements BeanRegistrar {
  const MailRegistrar();

  @override
  void register(BeanRegistry registry, Environment environment) {
    final host = environment.getProperty('mail.host');
    if (host != null) {
      registry.registerBean<Mailer>((_) => Mailer(host), name: 'mailer');
    }
  }
}

// Only for production: the imports are skipped in other profiles too.
@Configuration()
@Profile(['prod'])
@Import([LegacyBillingConfig, MailRegistrar])
class ProductionConfig {}

Parameters

In Spring (Java)

@Configuration
@Profile("prod")
@Import({LegacyBillingConfig.class, MailRegistrar.class})
class ProductionConfig {}

Differences that matter:

• An ImportSelector returns BeanModules, not class names, and receives no annotation metadata of the importing class.
• Registrars are created with their no-argument constructor. There is no reflection to pass the importing class's metadata.

See also

• @ComponentScan
• BeanRegistrar
• BeanModule
• @Configuration
• @Conditional, @Profile