### Environment

* Dubbo version: 3.0.6
* Operating System version: windows10
* Java version: jdk1.8

### Steps to reproduce this issue

String loadbalance() default ClusterRules.EMPTY;



* <b>This usage is recommended</b>.<br/>
 * It is more flexible on bean methods than on implementation classes, and is more compatible with Spring.
 * <pre>
 * &#64;Configuration
 * class ProviderConfiguration {
 *
 *     &#64;Bean
 *     &#64;DubboService(group="demo")
 *     public DemoService demoServiceImpl() {
 *         return new DemoServiceImpl();
 *     }
 * }
 * </pre>
 *
 * <b>2. Using on implementation class of service:  </b>
 * <pre>
 * &#64;DubboService(group="demo")
 * public class DemoServiceImpl implements DemoService {
 *     ...
 * }
 * </pre>
 *
 * This usage causes the implementation class to rely on the Dubbo module.
 *
 *
 * @since 2.7.7
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})