使用泛型作为自动装配限定符

除了 @Qualifier 注解之外，您还可以使用 Java 泛型作为一种隐式限定形式。例如，假设您有以下配置

  • Java

  • Kotlin

@Configuration
public class MyConfiguration {

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

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

	@Bean
	fun stringStore() = StringStore()

	@Bean
	fun integerStore() = IntegerStore()
}

假设前面的 bean 实现了一个泛型接口（即 Store<String> 和 Store<Integer>），您可以 @Autowire Store 接口，并且泛型用作限定符，如下例所示

  • Java

  • Kotlin

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

@Autowired
private Store<Integer> s2; // <Integer> qualifier, injects the integerStore bean
@Autowired
private lateinit var s1: Store<String> // <String> qualifier, injects the stringStore bean

@Autowired
private lateinit var s2: Store<Integer> // <Integer> qualifier, injects the integerStore bean

泛型限定符也适用于自动装配列表、Map 实例和数组。以下示例自动装配一个泛型 List

  • Java

  • Kotlin

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