如何在拥有对象（也就是@Autowired）上的注释条件下为@Autowire字段提供其他bean？

Question

I have a config class that provides two implemenations of the same base bean interface. I want these to be used conditionally based on what annotation the owning class was autowired with.

The usage of the "owning" class:

public class MyController
{
    @Autowired
    private OwnerInterface baseOwner;

    @Autowired
    @MyAnnotation
    private OwnerInterface specialOwner;
}

The owning class:

public class OwningClass implements OwnerInterface
{
    //This is the one I want to supply a conditional bean for
    @Autowired
    private MyBeanInterface someBean;
}

This is a pesudo-code of the config class:

@Configuration
public class ConfigClass
{
    @Bean
    //Should I use a different conditional?
    //And if I make a static method to use here, how would I pass the owning class to it?
    @ConditionalOnExpression(...elided...)
    public MyBeanInterface getNormalBeanInterface()
    {
        return new MyBeanInterfaceImpl();
    }

    @Bean
    @ConditionalOnExpression(...elided.../* MyAnnotation */)
    public MyBeanInterface getSpecialBeanInterface()
    {
        return new MyBeanInterfaceForMyAnnotation();
    }
}

For the conditional, is there a way to pass the owning object to it? I would use a static method like:

@ConditionalOnExpression(
    "#{T(MyAnnotationVerifier).isAnnotatedBy(ownignObject))}"
)

Is there a better solution?

I don't want to use AOP because that's during use of the application and adds overhead to every call. If I can instead provide the bean, then it will happen at startup when the objects are created.

Can I use a different @Conditional annotation to do this?

Answer 1

If the decision has to be made statically (like your @MyAnnotation), you can alternatively use @Primary

@Bean
@Primary
public MyBeanInterface getNormalBeanInterface()
{
    return new MyBeanInterfaceImpl();
}

@Bean
public MyBeanInterface getSpecialBeanInterface()
{
    return new MyBeanInterfaceForMyAnnotation();
}

This way, you can auto-wire by Type and it will always refer to the bean with @Primary

---

Alternative to this: use auto-wire by name

public class ConfigClass {
    @Bean
    public MyBeanInterface normalBean(){
        return new MyBeanInterfaceImpl();
    }

    @Bean
    public MyBeanInterface specialBean(){
        return new MyBeanInterfaceForMyAnnotation();
    }
}

public class MyController {
    @Autowired
    private OwnerInterface normalBean;

    @Autowired
    private OwnerInterface specialBean;
}

To Note here: the variable names ( specialBean / normalBean ) here in MyController match exactly with the @Bean methods in ConfigClass

Hope this helps you.