spring如何动态指定具体实现类

// 接口
public interface ServiceInterface {
  public void method();
}
 
// 具体两个实现类
@Service("aService")
public class AServiceImpl implements ServiceInterface {
 
  @Override
  public void method() {
    System.out.println("the impl is A");
  }
 
  @Override
  public String toString() {
    return "A";
  }
}
 
@Service("bService")
public class BServiceImpl implements ServiceInterface {
 
  @Override
  public void method() {
    System.out.println("the impl is B");
  }
   
  @Override
  public String toString() {
    return "B";
  }
 
}

@Service("register")
public class Register implements InitializingBean, ApplicationContextAware {
  private Map<String, ServiceInterface> serviceImplMap = new HashMap<>();
  private ApplicationContext applicationContext;
 
  // 获取spring的上下文
  @Override
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    this.applicationContext = applicationContext;
  }
 
  // 获取接口实现类的所有bean，并按自己定的规则放入map中
  @Override
  public void afterPropertiesSet() throws Exception {
    Map<String, ServiceInterface> beanMap = applicationContext.getBeansOfType(ServiceInterface.class);
    // 以下代码是将bean按照自己定的规则放入map中，这里我的规则是key：service.toString();value:bean
    // 调用时，参数传入service.toString()的具体字符串就能获取到相应的bean
    // 此处也可以不做以下的操作，直接使用beanMap,在调用时，传入bean的名称
    for (ServiceInterface serviceImpl : beanMap.values()) {
      serviceImplMap.put(serviceImpl.toString(), serviceImpl);
    }
  }
   
  public ServiceInterface getServiceImpl(String name) {
    return serviceImplMap.get(name);
  }
 
}

@Resource
Register register;
 
@Test
public void testService() {
  ServiceInterface service = register.getServiceImpl("A");
  service.method();
  ServiceInterface service2 = register.getServiceImpl("B");
  service2.method();
}

@Component("informerRegistry")
public final class InformerRegistry implements ApplicationContextAware{
 
  private ApplicationContext applicationContext;
 
  @Override
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    this.applicationContext = applicationContext;
  }
}