什么是RPC? RPC是Remote Procedure
Call的缩写，像Client-Servier一样的远程过程调用，也就是调用远程服务就跟调用本地服务一样方便，一般用于将程序部署在不同的机器上，供客户端进行调用。就像一个request-response调用系统一样简单。在面向对象编程的程序中，RPC也可以用Remote
method
invocation(RMI)来展现。为什么用它呢，因为随着分布式结构的普遍，越来越多的应用需要解耦，将不同的独立功能部署发布成不同的服务供调用。
**
它的主要流程是Client -> Client Stub -> Network -> Server Stub -> Server
执行完成之后再进行返回。 这里边比较重要的就是Clint Stub和Server
Stub，他们主要的作用就是将调用的方法和参数进行编码（Marshalling）序列化，将序列化后的数据通过网络发送给Server
Stub，然后等待Server回执。Server
Stub将受到的序列化字节进行解码（Unmarshaling）反序列化，然后再将参数传入到对应到的方法中执行，将得出的结果计算出来之后再进行返回，返回的过程和正向的过程类似。
通过RPC原理实现类的远程调用
client：
```
public class RpcImporter<S> {
@SuppressWarnings("unchecked")
public S importer(final Class<?> serviceClass,final InetSocketAddress addr){
return (S) Proxy.newProxyInstance(
serviceClass.getClassLoader(),//classloader
new Class<?>[] {serviceClass.getInterfaces()[0]},//目标类接口
//代理类对象
new InvocationHandler(){
@Override
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
Socket socket =null;
ObjectOutputStream output =null;
ObjectInputStream input=null;
try{
socket=new Socket();
socket.connect(addr);
//client数据序列化输出
output =new ObjectOutputStream(socket.getOutputStream());
output.writeUTF(serviceClass.getName());//className
output.writeUTF(method.getName());//methodname
output.writeObject(method.getParameterTypes());//param name
output.writeObject(args);
//接收数据
input =new ObjectInputStream(socket.getInputStream());
return input.readObject();
}finally{
if(socket != null)
socket.close();
if(output !=null)
output.close();
if(input !=null)
input.close();
}
}
});
}
}Service
public class RpcExporter {
//获取cpu核心数
static Executor executor =Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
//server
public static void exporter(String hostName,int port) throws IOException{
ServerSocket server=new ServerSocket();
server.bind(new InetSocketAddress(hostName,port));
try {
while(true){
executor.execute(new ExporterTask(server.accept()));
}
}finally{
server.close();
}
}
private static class ExporterTask implements Runnable{
Socket client =null;
public ExporterTask(Socket client){
this.client=client;
}
@Override
public void run() {
ObjectInputStream input=null;
ObjectOutputStream output=null;
try {
//反序列化
input =new ObjectInputStream(client.getInputStream());
String interfaceName=input.readUTF();
Class<?> service=Class.forName(interfaceName);
//method name
String methodName=input.readUTF();
//parameter type and argument
Class<?>[] parameterTypes=(Class<?>[])input.readObject();
Object[] arguments=(Object[])input.readObject();
//method
Method method =service.getMethod(methodName, parameterTypes);
//execute method
Object result=method.invoke(service.newInstance(), arguments);
//执行结果，序列化后返回到客户端
output =new ObjectOutputStream(client.getOutputStream());
output.writeObject(result);
} catch (Exception e) {
e.printStackTrace();
}finally{
if(output !=null)
try{
output.close();
}catch(IOException e){
e.printStackTrace();
}
if(input !=null)
try{
input.close();
}catch(IOException e){
e.printStackTrace();
}
if(client !=null)
try{
client.close();
}catch(IOException e){
e.printStackTrace();
}
}
}
}
}调用的接口与实现的类：
public interface EchoService {
String echo(String ping);
String addclient(String clientno);
String deleteclient(String clientno);
String editclient(String clientno);
String selectclient(String clientno);
String pagelist(String clientno);
}
public class EchoServiceImpl implements EchoService{
@Override
public String echo(String ping) {
return ping !=null ? ping + "--> I am ok." : " I am ko.";
}
@Override
public String addclient(String clientno) {
return clientno !=null ? clientno + "addclient" : "is null";
}
@Override
public String deleteclient(String clientno) {
// TODO Auto-generated method stub
return clientno !=null ? clientno + "deleteclient." : " I am ko.";
}
@Override
public String editclient(String clientno) {
// TODO Auto-generated method stub
return clientno !=null ? clientno + "editclient." : " I am ko.";
}
@Override
public String pagelist(String clientno) {
// TODO Auto-generated method stub
return clientno !=null ? clientno + "pagelist." : " I am ko.";
}
@Override
public String selectclient(String clientno) {
// TODO Auto-generated method stub
return clientno !=null ? clientno + "selectclient." : " I am ko.";
}
}测试：
public class Test {
public static void main(String[] args) throws Exception{
//服务端
new Thread (new Runnable(){
public void run(){
try{
RpcExporter.exporter("localhost", 8088);
}catch(Exception e){
e.printStackTrace();
}
}
}).start();
//客户端
RpcImporter<EchoService> importer=new RpcImporter<EchoService>();
//传入类与ip地址，返回代理
EchoService echo=importer.importer(EchoServiceImpl.class, new InetSocketAddress("localhost",8088));
System.out.println(Runtime.getRuntime().availableProcessors());
System.out.println(echo.echo("Are you ok?"));
}
}