I have a java config where ServiceB depends on ServiceA:
@Bean
ServiceA getServiceA() { return new ServiceA(); }
@Bean
ServiceB getServiceB() { return new ServiceB(getServiceA()); }
Then I want to declare ServiceA (but no ServiceB) as a component. I add @ScanPackage
to config and annotate ServiceA:
@Component
class ServiceA { .. }
How to declare method getServiceB()
now?
Spring auto-injects method parameters by type for Bean defining methods:
@Bean
ServiceB getServiceB(ServiceA serviceA) {
return new ServiceB(serviceA);
}
Now you don't have to worry about how ServiceA
is provided.
As Rohan already wrote in his answer , Spring's @Bean
annotation can inject dependencies of other Spring beans, in the same manner as constructor-based dependency injection does.
I would just add that there are also other possibilities to do dependency injection, when defining a bean in java config. @Configuration
annotated class is a Spring bean as any other Spring bean, so you can auto-wire a dependency, as is usually done in Spring and then use this dependency when defining your @Bean
, like:
@Autowired
private ServiceA serviceA;
@Bean
public ServiceB getServiceB() {
return new ServiceB(serviceA);
}
Since Spring Framework 4.3, you are also able to do constructor injection in @Configuration
classes - which is yet another way to inject dependencies.
See more details in spring documentation .
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