import java.util.concurrent.CompletableFuture;
public interface DemoService {
    /**
     * 同步处理的服务方法
     * @param name
     * @return
     */
    String sayHello(String name);

    /**
     * 用于异步处理的服务方法
     * @param name
     * @return
     */
    default CompletableFuture<String> sayHelloAsync(String name) {
        return CompletableFuture.completedFuture(sayHello(name));
    }
}

服务实现类如下:

import org.apache.dubbo.rpc.RpcContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.CompletableFuture;

public class DemoServiceImpl implements DemoService {
    private static final Logger logger = LoggerFactory.getLogger(DemoServiceImpl.class);

    @Override
    public String sayHello(String name) {
        logger.info("Hello " + name + ", request from consumer: " + RpcContext.getServiceContext().getRemoteAddress());
        return "Hello " + name + ", response from provider: " + RpcContext.getServiceContext().getLocalAddress();
    }

    @Override
    public CompletableFuture<String> sayHelloAsync(String name) {
        return null;
    }

}

import org.apache.dubbo.common.constants.CommonConstants;
import org.apache.dubbo.config.ApplicationConfig;
import org.apache.dubbo.config.MetadataReportConfig;
import org.apache.dubbo.config.ProtocolConfig;
import org.apache.dubbo.config.RegistryConfig;
import org.apache.dubbo.config.ServiceConfig;
import org.apache.dubbo.config.bootstrap.DubboBootstrap;
import org.apache.dubbo.demo.DemoService;

public class Application {
    public static void main(String[] args) throws Exception {
            startWithBootstrap();
    }
    private static void startWithBootstrap() {
        ServiceConfig<DemoServiceImpl> service = new ServiceConfig<>();
        service.setInterface(DemoService.class);
        service.setRef(new DemoServiceImpl());
        DubboBootstrap bootstrap = DubboBootstrap.getInstance();
        bootstrap.application(new ApplicationConfig("dubbo-demo-api-provider"))
            .registry(new RegistryConfig("zookeeper://127.0.0.1:2181"))
            .protocol(new ProtocolConfig(CommonConstants.DUBBO, -1))
            .service(service)
            .start()
            .await();
    }
}