ImportSelector class abstract interface

Code that chooses, at startup, which modules of beans to add.

Use it when a whole group of beans depends on the configuration, for example S3 storage or disk storage depending on a property. Each alternative is a BeanModule (a @ComponentScan of its own directory), and the selector returns the ones to load. Most applications use @Profile or conditions instead.

Put the class in @Import([...]) (it needs a no-argument constructor) or pass an instance to context.register(...). It may implement EnvironmentAware, BeanFactoryAware and ResourceLoaderAware; those are called before selectImports. It runs while the importing class is parsed, once that class's parse-phase conditions have matched. The selected modules are parsed at once, and their classes are read before the importing class, with their own conditions. They are not registered when the importing class is skipped in the registerBean phase, unless another kept class imports them too.

// The storage beans follow the `storage` property.
class StorageSelector implements ImportSelector, EnvironmentAware {
  late Environment _environment;

  @override
  void setEnvironment(Environment environment) =>
      _environment = environment;

  @override
  List<BeanModule> selectImports() =>
      _environment.getProperty('storage') == 's3' ? [s3Beans] : [diskBeans];
}

Spring (Java):

class StorageSelector implements ImportSelector, EnvironmentAware {
  public String[] selectImports(AnnotationMetadata metadata) {
    return new String[] {"s3".equals(env.getProperty("storage"))
        ? S3Config.class.getName() : DiskConfig.class.getName()};
  }
}

Unlike Spring it returns modules (there is no class loading by name) and gets no annotation metadata of the importing class.

Properties

hashCode → int

The hash code for this object.

no setter, inherited

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

selectImports() → List<BeanModule>

Returns the modules to load; an empty list adds nothing.

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited