Hadoop 原生的基于Writable序列化的RPC框架应用实例

# Hadoop 原生的基于Writable序列化的RPC框架应用实例

## 整体步骤
 - 创建一个继承`org.apache.hadoop.ipc.VersionedProtocol`接口的协议接口类
 - 实现协议接口类
 - 实现服务端代码
 - 实现客户端做对

## 创建协议接口类
```java
package me.cqc.hadoop.rpc;

import org.apache.hadoop.ipc.VersionedProtocol;

import java.io.IOException;

public interface ClientProtocol extends VersionedProtocol{
    long versionID = 1L; //这个字段名称不能改，框架底层被限定了

int add(int a, int b) throws IOException;
}

```

## 实现协议接口类
```java
package me.cqc.hadoop.rpc;

import org.apache.hadoop.ipc.ProtocolSignature;

import java.io.IOException;

public class ClientProtocolImpl implements ClientProtocol {
    @Override
    public int add(int a, int b) {
        System.out.printf("client request add method. a = %d, b = %d \n", a, b);
        return a + b;
    }

@Override
    public long getProtocolVersion(String s, long l) throws IOException {
        return versionID;
    }

@Override
    public ProtocolSignature getProtocolSignature(String s, long l, int i) throws IOException {
        return new ProtocolSignature(versionID, null);
    }
}

```

## 实现服务端代码
```java
package me.cqc.hadoop.rpc;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.ipc.RPC;

import java.io.IOException;
import java.net.InetAddress;

public class Server {
    public static void main(String[] args) throws IOException {
        String address = InetAddress.getLocalHost().getHostAddress();
        int port = 13073;
        Configuration conf = new Configuration();
        System.out.printf("server starting， address : %s, port : %d \n", address, port);
        RPC.Server server = new RPC.Builder(conf)
                .setProtocol(ClientProtocol.class)
                .setInstance(new ClientProtocolImpl())
                .setBindAddress(address)
                .setPort(port)
                .setNumHandlers(1)
                .build();
        server.start();
        System.out.println("server started");
    }
}

```

## 实现客户端代码
```java
package me.cqc.hadoop.rpc;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.ipc.RPC;

import java.io.IOException;
import java.net.InetSocketAddress;

public class Client {

public static void main(String[] args) throws IOException {
        int port = 13073;
        String address = "xxx.xxx.xxx.xxx";

Configuration conf = new Configuration();
        ClientProtocol client = RPC.getProxy(ClientProtocol.class
                , ClientProtocol.versionID
                , new InetSocketAddress(address, port)
                , conf);
        System.out.println(client.add(1,2));

}
}

```

阿川CH