Allow manually registered bean definitions to specify a generic type to participate in generics qualifier resolution [SPR-13898]

[spring-projects-issues]

Oliver Drotbohm opened SPR-13898 and commented

Currently the qualifier resolution inspecting generics is restricted to either the bean type or the return type of a factory methods (as implemented in GenericTypeAwareAutowireCandidateResolver.checkGenericTypeMatch(…)). However, if you want to register bean definitions for generic types manually (to back an @Enable… annotation for example) there's no way to pass the generics information to the container to prevent ambiguities from happening.

Take this scenario for example. declaring a PluginRegistry of the Spring Plugin library in Java configuration looks like this.

@Configuration
class Config {

  @Bean
  public PluginRegistry<MyPlugin, MyDelimiter> myPluginRegistry(List<? extends MyPlugin> plugins) {
    return OrderAwarePluginRegistry.create(plugins);
  }
}

With a bean definition like this the container considers the generics information returned at the method return type and can disambiguate the registry returned from a PluginRegistry<MyOtherPlugin> defined in the same way.

However, the library also provides a shortcut for this configuration to easily configure multiple registries:

@Configuration
@EnablePluginRegistries({MyPlugin.class, MyOtherPlugin.class})
class Config {}

The annotation implementation is backed by a PluginRegistriesBeanDefinitionRegistrar that registers BeanDefinition instances for each of the plugin types listed. However, it's currently impossible to forward the generics information which is totally available at this point to the container. It would be great if there was a way to predict a ResolvableType instead of a raw Class by some means on the BeanDefinition. Looks like a new method RootBeanDefinition.getResolvableType() could expose either a manually defined one or the one derived from the factory method's return type and thus simplify the check in getReturnTypeForFactoryMethod(…) to the assignability to the DependencyDescriptor.

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Issue Links:

• Allow programmatic registration of bean definitions with a ResolvableType [SPR-14580] #19149 Allow programmatic registration of bean definitions with a ResolvableType ("duplicates")

[spring-projects-issues]

Oliver Drotbohm commented

It looks like this scenario here could be implemented with the fixes for #19149 in place, right?

[spring-projects-issues]

Juergen Hoeller commented

Indeed, this is more or less asking for the same thing...