Question

I’m trying to use Spring IoC with an interface like this:

public interface ISimpleService<T> {     void someOp(T t);     T otherOp(); } 

Can Spring provide IoC based on the generic type argument T? I mean, something like this:

public class SpringIocTest {     @Autowired     ISimpleService<Long> longSvc;      @Autowired     ISimpleService<String> strSvc;     //... } 

Of course, my example above does not work:

expected single matching bean but found 2: [serviceLong, serviceString]     at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessAfterInstantiation(AutowiredAnnotationBeanPostProcessor.java:243)     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:957) 

My Question: is it possible to provide a similar functionality with minimum modifications to either the Interface or the implementing classes? I know for instance I can use @Qualifiers, but I want to keep things as simple as possible.

Answer 1

I do not believe this is possible due to erasure. We generally switched to strongly typed sub-interfaces when going for full-autowiring:

public interface LongService extends ISimpleService<Long> {} public interface StringService extends ISimpleService<String> {} 

Upon doing this switch we found we actually liked this pretty well, because it allows us to do ‘find usage’ tracking much better, something you loose with the generics interfaces.