Configuration class

Marks a class whose Bean methods create beans.

Use it for objects you cannot annotate yourself (a class from another package, a connection built from properties) or that need setup code: each @Bean method returns one bean, and its parameters are injected. The class itself is a bean too.

By default (proxyBeanMethods true) the container creates a generated subclass whose @Bean methods return the container's bean. So when one @Bean method calls another, it gets the existing singleton, not a second object (a prototype-scoped @Bean still gives a new instance per call). Static @Bean methods are not intercepted. Because of the subclass, a class with instance @Bean methods must be extendable (not final, sealed or interface) and have a public generative constructor; otherwise the build fails. With proxyBeanMethods false ("lite" mode) the methods run as written: take other beans as method parameters instead of calling the methods.

@Lazy, @Profile and conditions on the class apply to all its @Bean methods, unless a method says otherwise (@Lazy(false)).

@Configuration()
class DataConfig {
  // Opened with the URL from the configuration files.
  @Bean(initMethod: 'connect')
  Connection connection(@Value(r'${db.url}') String url) =>
      Connection(url);

  @Bean()
  UserStore userStore(Connection connection) => UserStore(connection);

  @Bean()
  Clock clock() => SystemClock();

  @Bean()
  Scheduler scheduler() => Scheduler(clock()); // the clock singleton
}

@Configuration(proxyBeanMethods: false)
class LiteConfig {
  @Bean()
  Clock clock() => SystemClock();
}

Spring (Java), where the subclass is made with CGLIB:

@Configuration
class DataConfig {
  @Bean(initMethod = "connect")
  Connection connection(@Value("${db.url}") String url) {
    return new Connection(url);
  }

  @Bean
  UserStore userStore(Connection connection) {
    return new UserStore(connection);
  }

  @Bean Clock clock() { return new SystemClock(); }

  @Bean Scheduler scheduler() { return new Scheduler(clock()); }
}

@Configuration(proxyBeanMethods = false)
class LiteConfig {
  @Bean Clock clock() { return new SystemClock(); }
}

Inheritance

• Object
• Component
• Configuration

Constructors

Configuration({String? name, bool proxyBeanMethods = true})

Declares the configuration class; name replaces the default bean name.

const

Properties

hashCode → int

The hash code for this object.

no setter, inherited

name → String?

The bean name; null gives the class name in lowerCamelCase.

final, inherited

proxyBeanMethods → bool

Whether a generated subclass makes @Bean methods return the container's beans (default true). With false the methods are called as written, which avoids the subclass and its restrictions.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited