就靠這幾段程式碼,帶你玩轉rpc通訊協議,不信你學不明白
阿新 • • 發佈:2020-09-07
RPC(Remote Procedure Call Protocol)——遠端過程呼叫協議,它是一種通過網路從遠端計算機程式上請求服務,而不需要了解底層網路技術的協議。該協議允許運行於一臺計算機的程式呼叫另一臺計算機的子程式,而程式設計師無需額外地為這個互動作用程式設計。RPC協議假定某些傳輸協議的存在,如TCP或UDP,為通訊程式之間攜帶資訊資料。在OSI網路通訊模型中,RPC跨越了傳輸層和應用層。RPC使得開發包括網路分散式多程式在內的應用程式更加容易。
2.基本概念
- RPC(Remote Procedure Call)遠端過程呼叫,簡單的理解是一個節點請求另一個節點提供的服務
- 本地過程呼叫:如果需要將本地student物件的age+1,可以實現一個addAge()方法,將student物件傳入,對年齡進行更新之後返回即可,本地方法呼叫的函式體通過函式指標來指定。
- 遠端過程呼叫:上述操作的過程中,如果addAge()這個方法在服務端,執行函式的函式體在遠端機器上,如何告訴機器需要呼叫這個方法呢?
今天,我們就通過一個例項程式碼進行演示,一步步的檢視,rpc的通訊是如何進行的,有興趣的朋友可以把程式碼進行實現,自己debug一下,檢視每一步的傳參
1
package com.mashibing.rpc.common;
import java.io.Serializable;
public class User implements Serializable {
private static final long serialVersionUID = 1L;
private Integer id;
private String name;
public User(Integer id, String name) {
this.id = id;
this.name = name;
}
public Integer getId() {
return id;
}
public String getName() {
return name;
}
public void setId(Integer id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
package com.mashibing.rpc.common;
public interface IUserService {
public User findUserById(Integer id);
}
package com.mashibing.rpc01;
import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;
public class UserServiceImpl implements IUserService {
@Override
public User findUserById(Integer id) {
return new User(id, "Alice");
}
}
package com.mashibing.rpc01;
import com.mashibing.rpc.common.User;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;
public class Client {
public static void main(String[] args) throws Exception {
Socket s = new Socket("127.0.0.1", 8888);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeInt(123);
s.getOutputStream().write(baos.toByteArray());
s.getOutputStream().flush();
DataInputStream dis = new DataInputStream(s.getInputStream());
int id = dis.readInt();
String name = dis.readUTF();
User user = new User(id, name);
System.out.println(user);
dos.close();
s.close();
}
}
2
package com.mashibing.rpc02;
import com.mashibing.rpc.common.User;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;
public class Stub {
public User findUserById(Integer id) throws Exception {
Socket s = new Socket("127.0.0.1", 8888);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeInt(123);
s.getOutputStream().write(baos.toByteArray());
s.getOutputStream().flush();
DataInputStream dis = new DataInputStream(s.getInputStream());
int receivedId = dis.readInt();
String name = dis.readUTF();
User user = new User(id, name);
dos.close();
s.close();
return user;
}
}
3
package com.mashibing.rpc03;
import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.Socket;
/**
* 而且Client的呼叫顯得不是很合理(Stub裡只有findById的程式碼),如果有個findByName的新方法,那麼就又得重新改進
* 下面這種寫法解決了方法增加的問題
*/
public class Stub {
public static IUserService getStub() {
InvocationHandler h = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Socket s = new Socket("127.0.0.1", 8888);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeInt(123);
s.getOutputStream().write(baos.toByteArray());
s.getOutputStream().flush();
DataInputStream dis = new DataInputStream(s.getInputStream());
int id = dis.readInt();
String name = dis.readUTF();
User user = new User(id, name);
dos.close();
s.close();
return user;
}
};
Object o = Proxy.newProxyInstance(IUserService.class.getClassLoader(), new Class[] {IUserService.class}, h);
return (IUserService)o;
}
}
4
package com.mashibing.rpc04;
import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.Socket;
/**
* 但是這裡僅僅實現了findByUserId的方法代理,如果要實現其他方法的代理該怎麼做呢?
* 這裡就要從協議層做出改進
*
* 伺服器端也要做出對應處理
*/
public class Stub {
public static IUserService getStub() {
InvocationHandler h = new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Socket s = new Socket("127.0.0.1", 8888);
ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());
String methodName = method.getName();
Class[] parametersTypes = method.getParameterTypes();
oos.writeUTF(methodName);
oos.writeObject(parametersTypes);
oos.writeObject(args);
oos.flush();
DataInputStream dis = new DataInputStream(s.getInputStream());
int id = dis.readInt();
String name = dis.readUTF();
User user = new User(id, name);
oos.close();
s.close();
return user;
}
};
Object o = Proxy.newProxyInstance(IUserService.class.getClassLoader(), new Class[] {IUserService.class}, h);
return (IUserService)o;
}
}
package com.mashibing.rpc04;
import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;
import java.io.*;
import java.lang.reflect.Method;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
private static boolean running = true;
public static void main(String[] args) throws Exception {
ServerSocket ss = new ServerSocket(8888);
while (running) {
Socket s = ss.accept();
process(s);
s.close();
}
ss.close();
}
private static void process(Socket s) throws Exception {
InputStream in = s.getInputStream();
OutputStream out = s.getOutputStream();
ObjectInputStream oos = new ObjectInputStream(in);
DataOutputStream dos = new DataOutputStream(out);
String methodName = oos.readUTF();
Class[] parameterTypes = (Class[])oos.readObject();
Object[] args = (Object[])oos.readObject();
IUserService service = new UserServiceImpl();
Method method = service.getClass().getMethod(methodName, parameterTypes);
User user = (User)method.invoke(service, args);
dos.writeInt(user.getId());
dos.writeUTF(user.getName());
dos.flush();
}
}
5
返回值用Object封裝,支援任意型別
就這樣,直到最後的server端獲取到資料,完成了一個數據傳輸,不知道大家能不能理解,最後,紙上得來終覺淺,我建議大家還是能夠可以自己實現一下。
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