Dubbo第一讲：从RPC到Dubbo框架详解

@Target({ElementType.TYPE}) //注解用在接口上
@Rentention(RententionPolicy.RUNTIME) //VM将在运行期也保留注释,因此可以通过反射机制读取注解的信息
@Component 
  public @interface RpcService{
    String value();  //使注解可以添加参数  一个字符串 
  }

@RpcService("HelloService")
public class HelloServiceImpl implements HelloService{
    public String hello(String name){
      return "Hello:"+name;}
}

public void setApplicationContext(ApplicationContext ctx)throws BeansException{
  //通过spring上下文环境获取被自定义注解的所有bean，存入map
  Map<String,Object> serviceBeanMap = ctx.getBeansWithAnnotation(RPCService.class);
    //遍历serviceBeanMap，获取注解的参数，将所有实现类实例，再存入一个handlerMap<接口名，实现类>
    if(MapUtils.isNotEmpty(serviceBeanMap)){
      for(Object serviceBean:serviceBeanMap.values()){
        String interfaceName = serviceBean.getClass().getAnnotation(RpcService.class).value().getName();
        handlerMap.put(interfaceName,serviceBean);
      }
    }
}

private Object handle(RpcRequest request)throws Throwable{
  //1、从request中解析出类名、方法名、参数类型、参数值；
  String className = request.getClassName();
  String methodName = request.getMethodName();
  Class<?>[] parameterTypes = request.getParameterTypes();
  Object[] parameters = request.getParameters();
  //2.根据类名，从handleMap里查询实现类对象；
  Object serviceBean = handlerMap.get(className);
  //3.根据类名加载接口类
  Class<?> forName = Class.forName(className);
  //3.获得接口类的指定方法和参数类型；
  Method method = forName.getMethod(methodName, parameterTypes);
  //4.invoke反射调用方法并返回（实现类对象，参数）
  return   method.invoke(serviceBean, parameters);
}

<context:component-scan base-package="com.zjut.rpc.sample.server"/>  //注解扫描，扫描路径下的类
<context:property-placeholder location="classpath:rpc.properties"/> //加载属性文件，存储zk地址
<bean id="serviceRegistry" class="com.zjut.rpc.registry.ServiceRegistry"> //管理 服务注册的对象
  <constructor-arg name="registryAddress" value="${registry.address}"/>
</bean>
<bean id="rpcServer" class="com.zjut.rpc.server.RpcServer">    //提供服务的对象，依赖注入服务注册对象
  <constructor-arg name="serverAddress" value="${server.address}"/>
  <constructor-arg name="serviceRegistry" ref="serviceRegistry"/>
</bean>

@autowired  
RpcProxy rpcProxy；//自动装配（在spring.xml按类型查找bean，注入到rpcProxy、默认按类型匹配）

@Autowired
private RpcProxy rpcProxy;
@Test 
public void helloTest1(){
  //调用代理对象的create方法，代理HelloService接口；因为肯定是实现该接口的对象，所以直接传对象；create名字自己定，可以是getProxy
  HelloService helloService = rpcProxy.create(HelloService.class);
  //调用代理的方法，内部执行invoke
  String result = helloService.hello("World");
  SYSo("服务器返回结果");
  SYSO(result);
}

public<T> T create(Class<?> interfaceClass){
   return(T) Proxy.newProxyInstance(interfaceClass.getClassLoader(),new Class<?>[]{interfaceClass},new InvocationHandler(){
      public Object invoke(Object proxy,Method method,Object[] args)throws Throwable{
        //创建RpcRequest，封装被代理类的属性
        RPCRequest request = new RpcRequest();
        request.setRequestId(UUID.randomUUID().toString());
        request.setClassName(method.getDeclaringClass().getName());
        request.setMethodName(method.getName());
        request.setParameterTypes(method.getParameterTypes());
        request.setParameters(args);
        //向zk查询服务器地址  host  port
        serverAddress = serviceDiscovery.discover();
        //创建RpcClient，netty连接服务器
        RpcClient client = new RpcClient(host, port);
        //request对象序列化并发送
        RpcResponse response = client.send(request);
        //等待返回结果response.getResult()
        if(response.isError()){
          throw response.getError();
        }else{
          return response.getResult();
        }
      }
    };
   )
}