Spring3的@Configuration不能@Inject组件扫描的bean

Question

This is my app.xml :

<context:component-scan base-package="destiny.web" />
<context:annotation-config/>

And there is a Dao (interface) , and DaoImpl (annotated with @Repository ) inside destiny.web package.

There is another Spring3's destiny.web.AppConfig class :

@Configuration
public class AppConfig
{
  @Inject
  private Dao daoImpl

  public AppConfig()
  {
    System.out.println("dao = " + daoImpl);
  }
}

It prints 'null' , why ?

I am sure all these beans/configuration/repositories are scanned. But it seems @Configuration doesn't know other scanned beans . Did I miss anything ?

I try to solve it by @ImportResource :

@Configuration
@ImportResource("classpath:app.xml")
public class AppConfig

But it seems causing cyclic bean scan and throws this exception :

{main} org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Only one AsyncAnnotationBeanPostProcessor may exist within the context.
Offending resource: class path resource [app.xml]

How to solve it ?

Thanks.

Answer 1

Spring will invoke constructor firstly before inject / autowiring the other component. therefore your dao is null while you print at the constructor, because the dao still not injected yet .

Have a try to create test application for your configapp.

public class Main {
    public static void main(String[] args) {
        ApplicationContext context =
            new ClassPathXmlApplicationContext("stackoverflow.xml");

        AppConfig appConfig = context.getBean(AppConfig.class);
        appConfig.getConfig("smtp.host");
    }
}

Answer 2

你有没有使用@Autowired注释而不是@Inject尝试它？