带有几个接口实现的Spring Autowire注释

Question

假设您有一个接口

public interface A {
  public void doSomething();
}

和两个实现类

@Component(value="aImpl1")
public class AImpl1 implements A {

}

@Component(value="aImpl2")
public class AImpl2 implements A{

}

@Component
public class MyClass {
  @Autowire
  A a;
}

Answer 1

假设您已经有数百个接口和实现（正如您在评论中所说），并且您不想重构所有代码······然后是一个棘手的问题...这是一个棘手的解决方案：

您可以创建自定义BeanDefinitionRegistryPostProcessor并实现方法PostProcessBeanDefinitionRegistry或PostProcessBeanFactory。

通过这种方式，您可以在实例化和注入所有bean定义之前访问它们。执行逻辑，找出每个接口的首选实现，然后将该接口设置为主要实现。

@Component
public class CustomBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {

    @Override
    public void postProcessBeanDefinitionRegistry(
            BeanDefinitionRegistry registry) throws BeansException {

          // this method can be used to set a primary bean, although 
          // beans defined in a @Configuration class will not be avalable here.

    }

    @Override
    public void postProcessBeanFactory(
            ConfigurableListableBeanFactory beanFactory) throws BeansException {     

        // here, all beans are available including those defined by @configuration, @component, xml, etc.

        // do some magic to somehow find which is the preferred bean name for each interface 
        // you have access to all bean-definition names with: beanFactory.getBeanDefinitionNames()
        String beanName = "aImpl2"; // let's say is this one

        // get the definition for that bean and set it as primary
        beanFactory.getBeanDefinition(beanName).setPrimary(true)

    }



}

另一方面，它们确实可以在PostProcessBeanFactory中使用。