dubbo学习笔记 十 dubbo-rpc

通过前面的dubbo-common之动态扩展，我们明白了会加载META-INF 目录下的文件。

接着来学习dubbo-rpc吧

Invoker

rpc调用远程实习类叫Invoker

public interface Invoker<T> extends Node {

/**
* get service interface.
*
* @return service interface.
*/
Class<T> getInterface();

/**
* invoke.
*
* @param invocation
* @return result
* @throws RpcException
*/
Result invoke(Invocation invocation) throws RpcException;

}

Exporter

用来获取invoker

public interface Exporter<T> {

/**
* get invoker.
*
* @return invoker
*/
Invoker<T> getInvoker();

/**
* unexport.
*
* <code>
* getInvoker().destroy();
* </code>
*/
void unexport();

}

Protocol

描述远程协议，定义远程操作

/*
* Copyright 1999-2011 Alibaba Group.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0 *
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.alibaba.dubbo.rpc;

import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.common.extension.Adaptive;
import com.alibaba.dubbo.common.extension.SPI;

/**
* Protocol. (API/SPI, Singleton, ThreadSafe)
*
* @author william.liangf
*/
@SPI("dubbo")
public interface Protocol {

/**
* 获取缺省端口，当用户没有配置端口时使用。
*
* @return 缺省端口
*/
int getDefaultPort();

/**
* 暴露远程服务：<br>
* 1. 协议在接收请求时，应记录请求来源方地址信息：RpcContext.getContext().setRemoteAddress();<br>
* 2. export()必须是幂等的，也就是暴露同一个URL的Invoker两次，和暴露一次没有区别。<br>
* 3. export()传入的Invoker由框架实现并传入，协议不需要关心。<br>
*
* @param <T> 服务的类型
* @param invoker 服务的执行体
* @return exporter 暴露服务的引用，用于取消暴露
* @throws RpcException 当暴露服务出错时抛出，比如端口已占用
*/
@Adaptive
<T> Exporter<T> export(Invoker<T> invoker) throws RpcException;

/**
* 引用远程服务：<br>
* 1. 当用户调用refer()所返回的Invoker对象的invoke()方法时，协议需相应执行同URL远端export()传入的Invoker对象的invoke()方法。<br>
* 2. refer()返回的Invoker由协议实现，协议通常需要在此Invoker中发送远程请求。<br>
* 3. 当url中有设置check=false时，连接失败不能抛出异常，并内部自动恢复。<br>
*
* @param <T> 服务的类型
* @param type 服务的类型
* @param url 远程服务的URL地址
* @return invoker 服务的本地代理
* @throws RpcException 当连接服务提供方失败时抛出
*/
@Adaptive
<T> Invoker<T> refer(Class<T> type, URL url) throws RpcException;

/**
* 释放协议：<br>
* 1. 取消该协议所有已经暴露和引用的服务。<br>
* 2. 释放协议所占用的所有资源，比如连接和端口。<br>
* 3. 协议在释放后，依然能暴露和引用新的服务。<br>
*/
void destroy();

}

Result

invoke结果

public interface Result {

/**
* Get invoke result.
*
* @return result. if no result return null.
*/
Object getValue();

/**
* Get exception.
*
* @return exception. if no exception return null.
*/
Throwable getException();

/**
* Has exception.
*
* @return has exception.
*/
boolean hasException();

/**
* Recreate.
*
* <code>
* if (hasException()) {
* throw getException();
* } else {
* return getValue();
* }
* </code>
*
* @return result.
* @throws if has exception throw it.
*/
Object recreate() throws Throwable;

/**
* @deprecated Replace to getValue()
* @see com.alibaba.dubbo.rpc.Result#getValue()
*/
@Deprecated
Object getResult();

/**
* get attachments.
*
* @return attachments.
*/
Map<String, String> getAttachments();

/**
* get attachment by key.
*
* @return attachment value.
*/
String getAttachment(String key);

/**
* get attachment by key with default value.
*
* @return attachment value.
*/
String getAttachment(String key, String defaultValue);

}

Invocation

远程调用入参

public interface Invocation {

/**
* get method name.
*
* @serial
* @return method name.
*/
String getMethodName();

/**
* get parameter types.
*
* @serial
* @return parameter types.
*/
Class<?>[] getParameterTypes();

/**
* get arguments.
*
* @serial
* @return arguments.
*/
Object[] getArguments();

/**
* get attachments.
*
* @serial
* @return attachments.
*/
Map<String, String> getAttachments();

/**
* get attachment by key.
*
* @serial
* @return attachment value.
*/
String getAttachment(String key);

/**
* get attachment by key with default value.
*
* @serial
* @return attachment value.
*/
String getAttachment(String key, String defaultValue);

/**
* get the invoker in current context.
*
* @transient
* @return invoker.
*/
Invoker<?> getInvoker();

}