@Bean注解方法中接口类型的注入采集

Question

使用Spring并给出几个实现公共接口的类，如何在方法级别引用使用@Bean注释实现该接口的所有类？

我希望检索所有实现实例，对每个实例应用一些逻辑，然后返回一个托管Map<String, Animal>对象，该对象可以注入到其他类或组件中。

公共接口

public interface Animal {

   String makeNoise();

}

public interface Person {

   String getOccupation();

}

动物实现#1

public Dog implements Animal {

   @Override
   String makeNoise() {
      return "Bark! Bark!";
   }

} 

动物实现#2

public Cat implements Animal {

   @Override
   String makeNoise() {
      return "Meow! Meow!";
   }

} 

Person实现#1

public Developer implements Person {

   @Override
   public String getOccupation() {
      return "Software Engineer";
   }

}

Person实现#2

public Lawyer implements Person {

   @Override
   public String getOccupation() {
      return "Litigator";
   }

}

Configuration

@Configuration
public class Initialize {

   //<snip> Beans created for Developer, and Lawyer objects </snip>

   @Bean
   Map<String, Developer> getDevelopers(List<Developer> developers) { // This is fine
      return new HashMap<>(...);
   }

   @Bean
   Map<String, Lawyer> getLawyers(List<Person> people) { // Spring wires this dependency fine
      return new HashMap<>(...);
   }

   @Bean
   Map<String, Dog> getOwners(Map<String, Person> owners) { // Spring reports it cannot auto-wire this dependency
                                                            // what do I do here? 
   }

}

任何帮助都将不胜感激，谢谢！

Answer 1

需要利用与List的协方差。见下面的伪代码/代码片段。

@Configuration
public class Initialize {

   //<snip> Beans created for Developer, and Lawyer objects </snip>

   @Bean
   Map<String, Developer> getDevelopers(List<Developer> developers) {
      return new HashMap<>(...);
   }

   @Bean
   Map<String, Lawyer> getLawyers(List<Person> people) {
      return new HashMap<>(...);
   }

   @Bean
   Map<String, Dog> getOwners(List<Map<String, ? extends Person>> owners) { // Spring will auto-wire the "owners" variable 
                                                                            // with all bean objects that match this signature 
                                                                            // (✅ Map<String, Lawyer>, ✅ Map<String, Developer> ...)

   }

}

资源：

• Spring: get all Beans of certain interface AND type

Answer 2

试试这种配置。这里唯一的一点是，集合中bean的顺序是随机的，不能被控制。

    @Configuration
    public class CollectionConfig {

        @Bean
        public Animal getCat() {
            return new Cat();
        }

        @Bean
        public Animal getDog() {
            return new Dog();
        }

        @Bean
        Map<String, Animals> gatherAnimals(List<Animals> animals) {
           // any code
        }
    }

下面是关于那个https://www.baeldung.com/spring-injecting-collections的更多信息