Just another possibility: Spring initializes bean by type not by name if you don't define bean with a name, which is ok if you use it by its type:
Producer:
@Service
public void FooServiceImpl implements FooService{}
Consumer:
@Autowired
private FooService fooService;
or
@Autowired
private void setFooService(FooService fooService) {}
but not ok if you use it by name:
ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
ctx.getBean("fooService");
It would complain: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'fooService' is defined
In this case, assigning name to @Service("fooService")
would make it work.