【Dubbo3技术专题】回顾Dubbo2.x的技术原理和功能实现及源码分析（温故而知新）（二）

<dubbo:service interface="com.foo.BarService" version="1.0.0" />

<dubbo:service interface="com.foo.BarService" version="2.0.0" />

<dubbo:reference id="barService" interface="com.foo.BarService" version="1.0.0" />

<dubbo:reference id="barService" interface="com.foo.BarService" version="2.0.0" />

<dubbo:reference id="barService" interface="com.foo.BarService" version="*" />

RegistryFactory registryFactory = ExtensionLoader.getExtensionLoader(RegistryFactory.class).getAdaptiveExtension();
Registry registry = registryFactory.getRegistry(URL.valueOf("zookeeper://10.20.153.10:2181"));
registry.register(URL.valueOf("override://0.0.0.0/com.foo.BarService?category=configurators&dynamic=false&application=foo&mock=force:return+null"));

<dubbo:service retries="2" />
或
<dubbo:reference retries="2" />
或
<dubbo:reference>
  <dubbo:method name="findFoo" retries="2" />
</dubbo:reference>

<dubbo:service cluster="failsafe" />
或
<dubbo:reference cluster="failsafe" />

<dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
   <version>1.4.4.RELEASE</version>
</dependency>

@SpringBootApplication
@EnableHystrix
public class ProviderApplication {

@Service(version = "1.0.0")
public class HelloServiceImpl implements HelloService {
    @HystrixCommand(commandProperties = {
     @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"),
     @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "2000") })
    @Override
    public String sayHello(String name) {
        // System.out.println("async provider received: " + name);
        // return "annotation: hello, " + name;
        throw new RuntimeException("Exception to show hystrix enabled.");
    }
}

@Reference(version = "1.0.0")
private HelloService demoService;
@HystrixCommand(fallbackMethod = "reliable")
public String doSayHello(String name) {
   return demoService.sayHello(name);
}
public String reliable(String name) {
   return "hystrix fallback value";
}

<!-- 提供方应用信息，用于计算依赖关系 -->
<dubbo:application name="uop" owner="uce"/>
<!-- 使用zookeeper注册中心暴露服务地址 -->
<dubbo:registry protocol="zookeeper" address="zookeeper://192.168.xx.xx:2181?backup=192.168.xx.xx:2182,192.168.xx.xx:2183" />
<!--dubbox中引入Kryo和FST这两种高效Java序列化实现，来逐步取代原生dubbo中的hessian2,如果使用kryo记得添加依赖 -->
<dubbo:protocol name="dubbo" serialization="kryo"  port="20990"  />
<!-- 定义服务提供者默认属性值 -->
<dubbo:provider timeout="5000" threadpool="fixed"  threads="100" accepts="1000" token="true"/>
<!-- 暴露服务接口 一个服务可以用多个协议暴露，一个服务也可以注册到多个注册中心-->
<!--Provider上尽量多配置Consumer端的属性，让Provider实现者一开始就思考Provider服务特点、服务质量的问题-->
<dubbo:service interface="com.yingjun.dubbox.api.UserService" ref="userService" />

public class DubboNamespaceHandler extends NamespaceHandlerSupport {
    static {
        Version.checkDuplicate(DubboNamespaceHandler.class);
    }
   @Override
    public void init() {
        registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
        registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
        registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
        registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
        registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
        registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
        registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
        registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
        registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
        registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser());
    }
}