rpc

        当初接触dubbo的时候,对梁飞大大佩服的简直不要不要的,doubbo梁飞团队搞的一个分布式框架,分布式服务直接的通信就少不了rpc,梁飞大大也写了一篇关于rpc入门小案例,十分简洁实用,特摘录做个笔记(梁飞-RPC框架几行代码就够了).

        RPC（Remote Procedure Call Protocol）——远程过程调用协议,它是一种通过网络从远程计算机程序上请求服务，而不需要了解底层网络技术的协议。RPC协议假定某些传输协议的存在，如TCP或UDP，为通信程序之间携带信息数据.(百度文库-rpc)

        RPC采用客户机/服务器模式。请求程序就是一个客户机，而服务提供程序就是一个服务器。首先，客户机调用进程发送一个有进程参数的调用信息到服务进程，然后等待应答信息。在服务器端，进程保持睡眠状态直到调用信息到达为止。当一个调用信息到达，服务器获得进程参数，计算结果，发送答复信息，然后等待下一个调用信息，最后，客户端调用进程接收答复信息，获得进程结果，然后调用执行继续进行。

       RPC基本原理:

1.调用客户端句柄；执行传送参数

2.调用本地系统内核发送网络消息

3.消息传送到远程主机

4.服务器句柄得到消息并取得参数

5.执行远程过程

6.执行的过程将结果返回服务器句柄

7.服务器句柄返回结果，调用远程系统内核

8.消息传回本地主机

9.客户句柄由内核接收消息

10.客户接收句柄返回的数据

看看梁大大的写的rpc小案例

/* * Copyright 2011 Alibaba.com All right reserved. This software is the * confidential and proprietary information of Alibaba.com ("Confidential * Information"). You shall not disclose such Confidential Information and shall * use it only in accordance with the terms of the license agreement you entered * into with Alibaba.com. */package com.alibaba.study.rpc.framework;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.net.ServerSocket;import java.net.Socket;/** * RpcFramework *  * @author william.liangf */public class RpcFramework {    /**     * 暴露服务     *      * @param service 服务实现     * @param port 服务端口     * @throws Exception     */    public static void export(final Object service, int port) throws Exception {        if (service == null)            throw new IllegalArgumentException("service instance == null");        if (port <= 0 || port > 65535)            throw new IllegalArgumentException("Invalid port " + port);        System.out.println("Export service " + service.getClass().getName() + " on port " + port);        ServerSocket server = new ServerSocket(port);        for(;;) {            try {                final Socket socket = server.accept();                new Thread(new Runnable() {                    @Override                    public void run() {                        try {                            try {                                ObjectInputStream input = new ObjectInputStream(socket.getInputStream());                                try {                                    String methodName = input.readUTF();                                    Class<?>[] parameterTypes = (Class<?>[])input.readObject();                                    Object[] arguments = (Object[])input.readObject();                                    ObjectOutputStream output = new ObjectOutputStream(socket.getOutputStream());                                    try {                                        Method method = service.getClass().getMethod(methodName, parameterTypes);                                        Object result = method.invoke(service, arguments);                                        output.writeObject(result);                                    } catch (Throwable t) {                                        output.writeObject(t);                                    } finally {                                        output.close();                                    }                                } finally {                                    input.close();                                }                            } finally {                                socket.close();                            }                        } catch (Exception e) {                            e.printStackTrace();                        }                    }                }).start();            } catch (Exception e) {                e.printStackTrace();            }        }    }    /**     * 引用服务     *      * @param <T> 接口泛型     * @param interfaceClass 接口类型     * @param host 服务器主机名     * @param port 服务器端口     * @return 远程服务     * @throws Exception     */    @SuppressWarnings("unchecked")    public static <T> T refer(final Class<T> interfaceClass, final String host, final int port) throws Exception {        if (interfaceClass == null)            throw new IllegalArgumentException("Interface class == null");        if (! interfaceClass.isInterface())            throw new IllegalArgumentException("The " + interfaceClass.getName() + " must be interface class!");        if (host == null || host.length() == 0)            throw new IllegalArgumentException("Host == null!");        if (port <= 0 || port > 65535)            throw new IllegalArgumentException("Invalid port " + port);        System.out.println("Get remote service " + interfaceClass.getName() + " from server " + host + ":" + port);        return (T) Proxy.newProxyInstance(interfaceClass.getClassLoader(), new Class<?>[] {interfaceClass}, new InvocationHandler() {            public Object invoke(Object proxy, Method method, Object[] arguments) throws Throwable {                Socket socket = new Socket(host, port);                try {                    ObjectOutputStream output = new ObjectOutputStream(socket.getOutputStream());                    try {                        output.writeUTF(method.getName());                        output.writeObject(method.getParameterTypes());                        output.writeObject(arguments);                        ObjectInputStream input = new ObjectInputStream(socket.getInputStream());                        try {                            Object result = input.readObject();                            if (result instanceof Throwable) {                                throw (Throwable) result;                            }                            return result;                        } finally {                            input.close();                        }                    } finally {                        output.close();                    }                } finally {                    socket.close();                }            }        });    }}用起来也像模像样： (1) 定义服务接口 /* * Copyright 2011 Alibaba.com All right reserved. This software is the * confidential and proprietary information of Alibaba.com ("Confidential * Information"). You shall not disclose such Confidential Information and shall * use it only in accordance with the terms of the license agreement you entered * into with Alibaba.com. */package com.alibaba.study.rpc.test;/** * HelloService *  * @author william.liangf */public interface HelloService {    String hello(String name);}(2) 实现服务 /* * Copyright 2011 Alibaba.com All right reserved. This software is the * confidential and proprietary information of Alibaba.com ("Confidential * Information"). You shall not disclose such Confidential Information and shall * use it only in accordance with the terms of the license agreement you entered * into with Alibaba.com. */package com.alibaba.study.rpc.test;/** * HelloServiceImpl *  * @author william.liangf */public class HelloServiceImpl implements HelloService {    public String hello(String name) {        return "Hello " + name;    }}(3) 暴露服务 /* * Copyright 2011 Alibaba.com All right reserved. This software is the * confidential and proprietary information of Alibaba.com ("Confidential * Information"). You shall not disclose such Confidential Information and shall * use it only in accordance with the terms of the license agreement you entered * into with Alibaba.com. */package com.alibaba.study.rpc.test;import com.alibaba.study.rpc.framework.RpcFramework;/** * RpcProvider *  * @author william.liangf */public class RpcProvider {    public static void main(String[] args) throws Exception {        HelloService service = new HelloServiceImpl();        RpcFramework.export(service, 1234);    }}(4) 引用服务 /* * Copyright 2011 Alibaba.com All right reserved. This software is the * confidential and proprietary information of Alibaba.com ("Confidential * Information"). You shall not disclose such Confidential Information and shall * use it only in accordance with the terms of the license agreement you entered * into with Alibaba.com. */package com.alibaba.study.rpc.test;import com.alibaba.study.rpc.framework.RpcFramework;/** * RpcConsumer *  * @author william.liangf */public class RpcConsumer {        public static void main(String[] args) throws Exception {        HelloService service = RpcFramework.refer(HelloService.class, "127.0.0.1", 1234);        for (int i = 0; i < Integer.MAX_VALUE; i ++) {            String hello = service.hello("World" + i);            System.out.println(hello);            Thread.sleep(1000);        }    }    }

        上述实现rpc功能:

1.服务方法暴露服务:通过ObjectInputStream将服务具体关键信息写入流中,通过socket功客户端调用

2.客户端动态代理服务,从socket中读取代理具体内容

3.服务端开启后(执行export),便循环创建线程和socket,server.accept()阻塞线程,知道有客户端请求,客户端利用动态代理通过socket传递必要的参数(方法名,参数,参数类型,没有传递实现类,因此无需进行序列化),服务端接受参数,利用反射进行解析,并执行得到结构,通过socket返回结果,代理对象接收结果,生成代理对象实例,(tcp/id的socket通讯保障时序问题)

         上述简单的rpc实现了远程调用,核心应该就是socket通讯,所谓的动态代理辅助获取socket流中具体信息,此例有个前提,服务端与客户端有共用的api(也就是interface),服务具体实现放在服务端.