给我的小迷妹解释什么是RPC

给我的小迷妹解释什么是RPC

   小迷妹：哥，我问你一个问题啊？

    我：啥问题啊？

   小迷妹：你最近嘴里面天天念叨的rpc 是啥啊？

   我：好，哥今天给你普及一下，什么是rpc。

   小迷妹：哇啊，哥哥你好棒啊。

   我：哈哈，还好还好，你不要这么崇拜我。

通俗解释RPC 是什么？

   RPC，就是Remote Procedure Call 远程过程调用 

   小迷妹：啥叫远程过程调用啊，咋搞的那么高深？

   我：我给你举个例子，就是说当你不想下楼吃饭的时候，然后拿起电话，叫了一个外卖，然后外卖小哥就把外卖送过来了，这个就是远程过程调用。

  小迷妹：哥，好像到中午了，刚好我不想下楼，那你帮我远程调用一下把。 

  我：。。。。。

精准解释RPC 是什么？

  现如今随着互联网的发展，更多的企业采用了分布式服务，解决了服务单点问题和服务功能一致性问题 ，以应对流量快速的增长。那么分布式服务之间 就会存在调用的问题。

举个例子

用户模块 是一个服务，交易模块 是一个服务。如果用户服务调用交易服务，因为它是分布到两个服务器上的是跨进程的，所以不能像调用本地方法那样，需要我们做一些处理，这就引入了rpc

来我们画张图

1.首先启动交易模块服务，会向外暴漏ip地址和port 端口号。

2.用户模块，通过动态代理，获取到接口和参数。

3.把获取到的接口和参数，以序列化的方式，调用交易模块暴漏出来的ip地址和port  底层通过网络协议，把序列化的数据，传输到交易模块。

4.交易模块，会把客户端传输过来的序列化数据，进行反序列化。

5.反序列化得到的接口和参数，在根据接口名称和参数，反射得到相应的实现类，然后调用实现类最后得到result。

6.最后把result放到数据流中，在根据刚刚建立的长连接，通过网络协议把result返回到客户端。

总结一下，rpc 主要解决以下两点：

1. 解决分布式系统中，服务之间的调用问题。
2. 远程调用时，要能够像本地调用一样方便，让调用者感知不到远程调用的逻辑。

手写RPC

 流程图

rpc-client 客户端

/*** Created by guyan on 2019/9/7 17:21*/
public class RemoteInvokeHandler implements InvocationHandler {private String ip;private int port;public RemoteInvokeHandler(String ip, int port) {this.ip = ip;this.port = port;}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {System.out.println("进入代理类");ReqParam param=new ReqParam();param.DeclaringClass().getName());param.Name());param.setParameters(args);System.out.println(&#String() = " + String());return new RpcNetSend(ip,port).send(param);}
}

/*** Created by guyan on 2019/9/7 17:23*/
public class RpcNetSend {private String ip;private int port;public RpcNetSend(String ip, int port) {this.ip = ip;this.port = port;}public Object send(ReqParam param) {Socket socket = null;ObjectOutputStream objectOutputStream = null;ObjectInputStream objectInputStream = null;Object result = null;try {socket = new Socket(ip, port);objectOutputStream = new OutputStream());objectOutputStream.writeObject(param);objectOutputStream.flush();objectInputStream = new InputStream());result = adObject();} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} finally {try {if (objectInputStream != null) {objectInputStream.close();}if (objectOutputStream != null) {objectOutputStream.close();}} catch (IOException e) {e.printStackTrace();}}return result;}
}

/*** Created by guyan on 2019/9/7 17:14*/
public class RpcProxyClient {public <T> T clientProxy(final Class<T> interfaceClass, String ip, int port) {return (T) ClassLoader(), new Class<?>[] { interfaceClass },new RemoteInvokeHandler(ip, port));}
}

*** Hello world!**/
public class App 
{public static void main( String[] args ){IMsgService iMsgService=new RpcProxyClient().clientProxy(IMsgService.class,"localhost",8080);String result = iMsgService.sayMsg("i am guyan");System.out.println("result = " + result);}
}

rpc-server 服务端：

/*** Created by guyan on 2019/9/7 11:15*/
public interface IMsgService {String sayMsg(String msg);String saveUser(UserDto user);
}

/*** Created by guyan on 2019/9/7 12:24*/
@RpcService(IMsgService.class)
public class IMsgServiceImpl implements IMsgService {@Overridepublic String sayMsg(String msg) {System.out.println("IMsgService.sayMsg the msg is " + msg);return "sayMsg="+msg;}@Overridepublic String saveUser(UserDto user) {System.out.println("IMsgService.saveUser the user is" + user);return "SUCCESS";}
}

/*** Created by guyan on 2019/9/8 15:33*/
public class RpcProxyServer01 implements InitializingBean, ApplicationContextAware {private ExecutorService executorService = wCachedThreadPool();/*** 端口号*/private int port;/*** key:serviceName value:service实例化*/private ConcurrentMap<String,Object> map=new ConcurrentHashMap<>();public RpcProxyServer01(int port) {this.port = port;}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("spring bean 初始化之后");ServerSocket socketServer = null;try {socketServer = new ServerSocket(port);while (true) {Socket accept = socketServer.accept();executorService.submit(new ProcessorHandler(accept, map));}} catch (IOException e) {e.printStackTrace();} finally {if (socketServer != null) {try {socketServer.close();} catch (IOException e) {e.printStackTrace();}}}}@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {System.out.println("spring 手动注入!");Map<String, Object> beans = BeansWithAnnotation(RpcService.class);if (beans.isEmpty()){return;}for(Object bean:beans.values()){RpcService rpcService = Class().getAnnotation(RpcService.class);String serviceName = rpcService.value().getName();map.put(serviceName,bean);}}
}

/*** Created by guyan on 2019/9/7 14:03*/
public class ProcessorHandler implements Runnable {private Socket socket;/*** key:serviceName value:service实例化*/private ConcurrentMap<String, Object> map = new ConcurrentHashMap<>();public ProcessorHandler(Socket socket, ConcurrentMap<String, Object> map) {this.socket = socket;this.map = map;}@Overridepublic void run() {System.out.println("进入处理类");ObjectInputStream objectInputStream = null;ObjectOutputStream objectOutputStream = null;try {objectInputStream = new InputStream());ReqParam reqParam = (ReqParam) adObject();Object result = invoke(reqParam, map);objectOutputStream = new OutputStream());objectOutputStream.writeObject(result);objectOutputStream.flush();} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} finally {try {if (objectInputStream != null) {objectInputStream.close();}if (objectOutputStream != null) {objectOutputStream.close();}} catch (IOException e) {e.printStackTrace();}}}/*** 通过反射机制找到相应的方法** @param param* @return*/private Object invoke(ReqParam param, ConcurrentMap<String, Object> map) {System.out.println("param = " + param);Object service = (ClassName());if (null == service) {throw new NullPointerException("the service is null,the service name is=[{}]" + ClassName());}Object[] parameters = Parameters(); //获取到参数Class<?>[] types = new Class[parameters.length]; //获取到参数类型for (int i = 0; i < parameters.length; i++) {types[i] = parameters[i].getClass(); //存到class type 数组中}Object result = null;try {Class clazz = Class.ClassName()); //根据类名反射出classMethod method = MethodName(), types); //class 根据方法名和参数获取相应的方法result = method.invoke(service, parameters); //通过传进来的实例类，和参数获取结果} catch (ClassNotFoundException e) {e.printStackTrace();} catch (NoSuchMethodException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}return result;}
}

*** Hello world!*/
public class App {public static void main(String[] args) {ApplicationContext applicationContext=new AnnotationConfigApplicationContext(SpringConfig.class);((AnnotationConfigApplicationContext) applicationContext).start();System.out.println("spring 初始化成功");}
}