Using Generics as Autowiring Qualifiers

In addition to the @Qualifier annotation, you can use Java generic types as an implicit form of qualification. For example, suppose you have the following configuration:

Java

@Configuration
public class MyConfiguration {

  @Bean
  public StringStore stringStore() {
    return new StringStore();
  }

  @Bean
  public IntegerStore integerStore() {
    return new IntegerStore();
  }
}

Assuming that the preceding beans implement a generic interface, (that is, Store<String> and Store<Integer>), you can @Autowire the Store interface and the generic is used as a qualifier, as the following example shows:

Java

@Autowired
private Store<String> s1; // <String> qualifier, injects the stringStore bean

@Autowired
private Store<Integer> s2; // <Integer> qualifier, injects the integerStore bean

Generic qualifiers also apply when autowiring lists, Map instances and arrays. The following example autowires a generic List:

Java

// Inject all Store beans as long as they have an <Integer> generic
// Store<String> beans will not appear in this list
@Autowired
private List<Store<Integer>> s;