创建RequestScope bean或回退到单例

Question

I need to create RequestScope bean to handle web code in a specific way, however this code can sometimes be called from non web thread and in that case I need to use standard Singleton.

Is there any good pattern to fallback during bean creation process based on the web thread availability?

The only thing that I can think of at this moment is to try to create bean with BeanFactory.getBean and return Singleton on BeanCreationException .

Answer 1

The solution below allows to get singleton or get/create request scope bean based on the execution context.

interface Consumer{}
class SingletonConsumer implements Consumer{}
class WebRequestBasedConsumer implements Consumer{}


class ConsumerFactory {
    private final BeanFactory beanFactory;
    private final SingletonConsumer singletonConsumer;

    Consumer getConsumer() {
        if (RequestContextHolder.getRequestAttributes() != null) {
            return beanFactory.getBean(WebRequestBasedConsumer.class);
        }
        return singletonConsumer;
    }
}

Answer 2

If I understand your requirement correctly, you can define two beans of the same class but configured them with different bean names and different scopes . Then use @Qualifer to differentiate which bean (ie which scoped of the bean) you want to inject.

For example ,the bean definitions look like:

@Bean(name="singletonFoo")
@Scope(scopeName = "singleton") //can omit it as the default scope is singleton already.
public Foo singletonFoo(){

}

@Bean(name="requestScopedFoo")
@Scope(scopeName = "request")
public Foo requestScopedFoo(){

}

Then to inject singleton bean :

@Autowired
@Qualifier("singletonFoo")
private Foo foo;

And to inject requested scoped bean:

@Autowired
@Qualifier("requestScopedFoo")
private Foo foo;