netty 的 Google protobuf 开发
根据上一篇博文 Google Protobuf 使用 Java 版 netty 集成 protobuf 的方法非常简单.代码如下:
server
package protobuf.server.impl; import io.netty.bootstrap.ServerBootstrap; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOption; 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; import object.server.impl.SubReqServer; import object.server.impl.SubScriptReqProto; public class SubReqProtobufServer { public void start(int port) { NioEventLoopGroup workGroup = new NioEventLoopGroup(); NioEventLoopGroup bossGroup = new NioEventLoopGroup(); ServerBootstrap bootstrap = new ServerBootstrap(); bootstrap.group(bossGroup, workGroup); bootstrap.channel(NioServerSocketChannel.class); // 配置 NioServerSocketChannel 的 tcp 参数, BACKLOG 的大小 bootstrap.option(ChannelOption.SO_BACKLOG, 100); bootstrap.handler(new LoggingHandler(LogLevel.INFO)); bootstrap.childHandler(new ChannelInitializer<SocketChannel>() { protected void initChannel(SocketChannel ch) throws Exception { /* * 首先添加 ProtobufVarint32FrameDecoder 处理器 , 它主要用于半包处理 */ ch.pipeline().addLast(new ProtobufVarint32FrameDecoder()); /* * 然后添加 ProtobufDecoder 解码器 , * 他的参数com.google.protobuf.MessageLite 实际上就是要告诉 ProtobufDecoder * 需要解码的目标类是什么,否则仅仅从字节数组中是无法判断出需要解码的目标类型信息 */ ProtobufDecoder protobufDecoder = new ProtobufDecoder( SubScriptReqProto.SubScriptReq.getDefaultInstance()); ch.pipeline().addLast(protobufDecoder); ch.pipeline().addLast( new ProtobufVarint32LengthFieldPrepender()); ch.pipeline().addLast(new ProtobufEncoder()); ch.pipeline().addLast(new SubReqProtobufHandler()); } }); // 绑定端口,随后调用它的同步阻塞方法 sync 等等绑定操作成功,完成之后 Netty 会返回一个 ChannelFuture // 它的功能类似于的 Future,主要用于异步操作的通知回调. ChannelFuture channelFuture; try { channelFuture = bootstrap.bind(port).sync(); // 等待服务端监听端口关闭,调用 sync 方法进行阻塞,等待服务端链路关闭之后 main 函数才退出. channelFuture.channel().closeFuture().sync(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { bossGroup.shutdownGracefully(); workGroup.shutdownGracefully(); } } public static void main(String[] args) { SubReqProtobufServer server = new SubReqProtobufServer(); server.start(9091); } }
serverHandler
package protobuf.server.impl; import object.server.impl.SubScriptReqProto; import object.server.impl.SubScriptRespProto; import io.netty.channel.ChannelHandlerAdapter; import io.netty.channel.ChannelHandlerContext; public class SubReqProtobufHandler extends ChannelHandlerAdapter { @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { cause.printStackTrace(); ctx.close(); } @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { try { SubScriptReqProto.SubScriptReq req = (SubScriptReqProto.SubScriptReq) msg; System.out.println("SubReqProtobufHandler : " + req); ctx.writeAndFlush(resp(req.getSubReqID())); } catch (Exception e) { e.printStackTrace(); throw e; } } private Object resp(int subReqID) { SubScriptRespProto.SubScriptResp.Builder builder = SubScriptRespProto.SubScriptResp .newBuilder(); builder.setSubReqID(subReqID); builder.setDesc("desc"); builder.setRespCode(2); return builder.build(); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush(); } }
client
package protobuf.client.impl; import io.netty.bootstrap.Bootstrap; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOption; 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.ObjectEncoder; import object.client.impl.SubReqClient; import object.server.impl.SubScriptReqProto; import object.server.impl.SubScriptRespProto; public class SubReqProtobufClient { public void connect(String host, int port) { NioEventLoopGroup workGroup = new NioEventLoopGroup(); Bootstrap bootstrap = new Bootstrap(); bootstrap.group(workGroup); bootstrap.channel(NioSocketChannel.class); bootstrap.option(ChannelOption.TCP_NODELAY, true); bootstrap.handler(new ChannelInitializer<SocketChannel>() { @Override protected void initChannel(SocketChannel ch) throws Exception { /* * 禁止堆类加载器进行缓存,他在基于 OSGI 的动态模块化编程中经常使用,由于 OSGI 可以进行热部署和热升级,当某个 * bundle * 升级后,它对应的类加载器也将一起升级,因此在动态模块化的编程过程中,很少对类加载器进行缓存,因为他随时可能会发生变化. */ ch.pipeline().addLast(new ProtobufVarint32FrameDecoder()); ch.pipeline().addLast( new ProtobufDecoder(SubScriptRespProto.SubScriptResp .getDefaultInstance())); ch.pipeline().addLast( new ProtobufVarint32LengthFieldPrepender()); ch.pipeline().addLast(new ProtobufEncoder()); ch.pipeline().addLast(new SubReqClientHandler()); } }); // 发起异步链接操作 ChannelFuture future; try { future = bootstrap.connect(host, port).sync(); // 等待客户端链路关闭 future.channel().closeFuture().sync(); } catch (InterruptedException e) { e.printStackTrace(); } finally { workGroup.shutdownGracefully(); } } public static void main(String[] args) { new SubReqProtobufClient().connect("localhost", 9091); } }
clientHandler
package protobuf.client.impl; import io.netty.channel.ChannelHandlerAdapter; import io.netty.channel.ChannelHandlerContext; import object.server.impl.SubScriptReqProto; public class SubReqClientHandler extends ChannelHandlerAdapter { @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { cause.printStackTrace(); ctx.close(); } @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { try { SubScriptReqProto.SubScriptReq.Builder builder = SubScriptReqProto.SubScriptReq .newBuilder(); for (int i = 0; i < 100; i++) { builder.setSubReqID(999 + i); builder.setAddress("address" + i); builder.setProductName("productvalue" + i); builder.setUserName("userName" + i); ctx.writeAndFlush(builder.build()); } } catch (Exception e) { e.printStackTrace(); } } @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { System.out.println("SubReqClientHandler : " + msg); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush(); } }
使用 ProtoBuf 的注意事项:
ProtobufDecode 只负责解码,它不支持半包读写,因此,在 protoBuf 前一定要一个能处理半包读写的处理器.他有三种方法可以选择:
- 使用 Netty 提供的 ProtobufVarint32FrameDecoder;
- 继承 Netty 提供的通用半包解码器 LengthFieldBasedFrameDecoder;
- 继承 ByteToMessageDecoder 类,自己处理半包消息
以上内容出自 : <Netty 权威指南
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