Netty 权威指南之Google protobuf 编解码
本章相关知识点：
Google 的protobuf 在业界非常流行，很多的商业项目选址使用protobuf作为编解码框架，这里一起回顾一下protobuf 框架的优点：
1、结构化数据存储（类似XML和JSON）
2、高效编码性能
3、语言无法、平台无法、拓展性好
4、官方支持Java、C++和Python
本章学习目标：
1、Protobuf 开发入门
2、开发支持Protobuf 的Netty 服务端
3、开发支持Protobuf 的Netty 客户端
4、运行基于Netty 开发的Protobuf 应用
第一节:Protobuf 开发入门
Protobuf 入门
protobuf 是一个灵活、高效、结构化的数据序列化框架。相比XML等传统序列化工具，它更小、更快、更简单.Protobuf支持数据结构化一次编译可以到处使用，甚至是跨语言使用，通过代码生成工具可以自动生成不同语言版本的源代码，甚至可以在不同的版本数据结构进程中进行数据传递，实现数据结构的前向兼容。
Protobuf 开发环境搭建
1、首先先下载protobuf 的windows 版本
2、protoc.exe 主要根据.proto文件生成代码，我们以图书订购流程为例，定义SubscribeReq.proto和SubscribeResp.proto，数据定义格式如下：
SubscribeResp.proto
option java_package="com.nio.serlizable";
option java_outer_classname="SubscribeRespProto";
message SubscribeResp{
required int32 subReqId = 1;
required int32 respCode = 2;
required string desc = 3;
}
option java_package="com.nio.serlizable";
option java_outer_classname="SubscribeReqProto";
message SubscribeReq{
required int32 subReqId = 1;
required string userName = 2;
required string productName = 3;
repeated string address = 4;
}
4、将生成的的POJO代码SubscribeReqProto.java和SubscribeRespProto.java复制到对应的IDEA14 项目当中。
5、到此，我们已经完成对google protobuf 开发环境搭建工作，我们接下来通过一个简单的Demo 来了解Protobuf 类库使用。
package com.nio.protobuf;
import java.util.ArrayList;
import java.util.List;
/**
* Created by vixuan-008 on 2015/6/24.
*/
public class TestSubscribeReq {
public static void main(String[] args)throws Exception{
SubscribeReqProto.SubscribeReq req=createSubscribeReq();
System.out.println("Before encode:"+req.toString());
SubscribeReqProto.SubscribeReq result=decode(encode(req));
System.out.println("decode cotent is:"+result.toString());
}
private static byte[] encode(SubscribeReqProto.SubscribeReq req){
return req.toByteArray();
}
private static SubscribeReqProto.SubscribeReq decode(byte[] body) throws Exception{
return SubscribeReqProto.SubscribeReq.parseFrom(body);
}
private static SubscribeReqProto.SubscribeReq createSubscribeReq(){
SubscribeReqProto.SubscribeReq.Builder builder= SubscribeReqProto.SubscribeReq.newBuilder();
builder.setSubReqId(1);
builder.setUserName("zhouzhigang");
builder.setProductName("Netty Book");
List address=new ArrayList();
address.add("湖南长沙");
address.add("湖南株洲");
address.add("湖南湘潭");
builder.addAllAddress(address);
return builder.build();
}
}
首先我们看如何创建 SubscribeReqProto.SubscribeReq的实例，通过SubscribeReqProto.SubscribeReq的静态方法newBuilder创建SubscribeReqProto.SubscribeReq的Builder实例,通过Builder构造器对SubscribeReq的属性进行相关设置，对于集合类型，通过addAllXXX()方法可以将集合对象添加到对象属性当中。
编码通过调用SubscribeReqProto.SubscribeReq实例的toByteArray方法，即可将SubscribeReq对象编码为byte数组，使用非常方便。
解码通过调用SubscribeReqProto.SubscribeReq的静态方法parseFrom将二进制数组解码为原始数据对象。
6、Protobuf 测试程序效果截图:
第二节:开发支持Protobuf 的Netty 服务端
SubRespProServer.java源代码（Handler 存在问题可能需要修改）
package com.nio.server;
import com.nio.handler.SubRespProHandler;
import com.nio.protobuf.SubscribeReqProto;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.protobuf.ProtobufDecoder;
import io.netty.handler.codec.protobuf.ProtobufEncoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32FrameDecoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
/**
* Created by vixuan-008 on 2015/6/24.
*/
public class SubRespProServer {
public static void main(String[] args)throws Exception{
int port=15444;
new SubRespProServer().bind(port);
}
public void bind(int port)throws Exception{
//配置服务端的NIO线程池
EventLoopGroup bossGroup=new NioEventLoopGroup();
EventLoopGroup workGroup=new NioEventLoopGroup();
try{
ServerBootstrap b=new ServerBootstrap();
b.group(bossGroup, workGroup);
b.channel(NioServerSocketChannel.class);
b.option(ChannelOption.SO_BACKLOG, 100);
b.handler(new LoggingHandler(LogLevel.INFO));
b.childHandler(new ChannelInitializer() {
@Override
protected void initChannel(SocketChannel socketChannel) throws Exception {
socketChannel.pipeline().addLast(new ProtobufVarint32FrameDecoder());
socketChannel.pipeline().addLast(new ProtobufDecoder(SubscribeReqProto.SubscribeReq.getDefaultInstance()));
socketChannel.pipeline().addLast(new ProtobufVarint32LengthFieldPrepender());
socketChannel.pipeline().addLast(new ProtobufEncoder());
socketChannel.pipeline().addLast(new SubRespProHandler());
}
});
//绑定端口，等待同步成功
ChannelFuture f=b.bind(port).sync();
//等待服务端关闭监听端口
f.channel().closeFuture().sync();
}finally {
//释放线程池资源
bossGroup.shutdownGracefully();
workGroup.shutdownGracefully();
}
}
}
package com.nio.handler;
import com.nio.protobuf.SubscribeReqProto;
import com.nio.protobuf.SubscribeRespProto;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
/**
* Created by vixuan-008 on 2015/6/24.
*/
public class SubRespProHandler extends ChannelHandlerAdapter {
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
super.channelActive(ctx);
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
SubscribeReqProto.SubscribeReq req=(SubscribeReqProto.SubscribeReq)msg;
System.out.println("server receiver client message is:"+req.toString());
ctx.writeAndFlush(resp(req.getSubReqId()));
}
private SubscribeRespProto.SubscribeResp resp(int subReqId)throws Exception{
SubscribeRespProto.SubscribeResp.Builder resp= SubscribeRespProto.SubscribeResp.newBuilder();
resp.setSubReqId(subReqId);
resp.setRespCode(0);
resp.setDesc("Netty Book order succeed 3 day later,sent to the designated adderss");
return resp.build();
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
super.channelReadComplete(ctx);
}
}
第三节: 开发支持Protobuf 的Netty 客户端
package com.nio.client;
import com.nio.handler.SubReqProHandler;
import com.nio.handler.SubReqServerHandler;
import com.nio.protobuf.SubscribeRespProto;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.protobuf.ProtobufDecoder;
import io.netty.handler.codec.protobuf.ProtobufEncoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32FrameDecoder;
import io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;
/**
* Created by vixuan-008 on 2015/6/24.
*/
public class SubReqProClient {
public static void main(String[] args)throws Exception{
int port=15444;
new SubReqProClient().bind(port, "127.0.0.1");
}
public void bind(int port,String host)throws Exception{
//配置客户端NIO线程池
EventLoopGroup workGroup=new NioEventLoopGroup();
try{
io.netty.bootstrap.Bootstrap b=new io.netty.bootstrap.Bootstrap();
b.group(workGroup);
b.channel(NioSocketChannel.class);
b.option(ChannelOption.TCP_NODELAY,true);
b.handler(new ChannelInitializer() {
@Override
protected void initChannel(SocketChannel socketChannel) throws Exception {
socketChannel.pipeline().addLast(new ProtobufVarint32FrameDecoder());
socketChannel.pipeline().addLast(new ProtobufDecoder(SubscribeRespProto.SubscribeResp.getDefaultInstance()));
socketChannel.pipeline().addLast(new ProtobufVarint32LengthFieldPrepender());
socketChannel.pipeline().addLast(new ProtobufEncoder());
socketChannel.pipeline().addLast(new SubReqProHandler());
}
});
//发起异步连接操作
ChannelFuture f=b.connect(host,port).sync();
//等待客户端链路关闭
f.channel().closeFuture().sync();
}finally {
//释放NIO 线程组
workGroup.shutdownGracefully();
}
}
}
package com.nio.handler;
import com.nio.protobuf.SubscribeReqProto;
import com.nio.protobuf.SubscribeRespProto;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import java.util.ArrayList;
import java.util.List;
/**
* Created by vixuan-008 on 2015/6/24.
*/
public class SubReqProHandler extends ChannelHandlerAdapter {
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
for(int i=0;i<10;i++){
ctx.write(subReq(i));
}
ctx.flush();
}
private SubscribeReqProto.SubscribeReq subReq(int i){
SubscribeReqProto.SubscribeReq.Builder req=SubscribeReqProto.SubscribeReq.newBuilder();
req.setProductName("Netty Book");
req.setUserName("zhouzhigang");
req.setSubReqId(i);
List address=new ArrayList();
address.add("china");
address.add("usa");
address.add("france");
req.addAllAddress(address);
return req.build();
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
System.out.println("Receiver server message is:"+msg);
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
}
第四节: 运行基于Netty 开发的Protobuf 应用
服务端截图:
Protobuf 使用注意事项：
1、ProtobufDecoder仅仅负责解码，它不支持读半包。因此，在ProtobufDecode前面，一定要有能够处理读半包的解码器，有三种方式可以选择.
使用Netty提供的ProtobufVarint32FrameDecoder，它可以处理半包消息：
集成Netty提供的通用半包解码器LengthFieldBasedFrameDecoder;
继承ByteMessageDecoder类，自己处理半包消息。
如果你只使用ProtobufDecoder解码器而忽视对半包消息处理，程序是不能正常运行的。今天的学习就到这里