Netty4.0学习笔记系列之四：混合使用coder和handler

http://blog.csdn.net/u013252773/article/details/21564301

Handler如何使用在前面的例子中已经有了示范，那么同样是扩展自ChannelHandler的Encoder和Decoder，与Handler混合后又是如何使用的？本文将通过一个实际的小例子来展示它们的用法。

该例子模拟一个Server和Client，两者之间通过http协议进行通讯，在Server内部通过一个自定义的StringDecoder把httprequest转换成String。Server端处理完成后，通过StringEncoder把String转换成httpresponse，发送给客户端。具体的处理流程如图所示：

其中红色框中的Decoder、Encoder及request都是Netty框架自带的，灰色框中的三个类是我自己实现的。

Server端的类有：Server StringDecoder BusinessHandler StringEncoder四个类。

1、Server 启动netty服务，并注册handler、coder，注意注册的顺序：

 package com.guowl.testmulticoderandhandler;

 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.http.HttpRequestDecoder;
 import io.netty.handler.codec.http.HttpResponseEncoder;

 // 测试coder 和 handler 的混合使用
 public class Server {
     public void start(int port) throws Exception {
         EventLoopGroup bossGroup = new NioEventLoopGroup();
         EventLoopGroup workerGroup = new NioEventLoopGroup();
         try {
             ServerBootstrap b = new ServerBootstrap();
             b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
                     .childHandler(new ChannelInitializer() {
                                 @Override
                                 public void initChannel(SocketChannel ch) throws Exception {
                                     // 都属于ChannelOutboundHandler，逆序执行
                                     ch.pipeline().addLast(new HttpResponseEncoder());
                                     ch.pipeline().addLast(new StringEncoder());

                                     // 都属于ChannelIntboundHandler，按照顺序执行
                                     ch.pipeline().addLast(new HttpRequestDecoder());
                                     ch.pipeline().addLast(new StringDecoder());
                                     ch.pipeline().addLast(new BusinessHandler());
                                 }
                             }).option(ChannelOption.SO_BACKLOG, 128)
                     .childOption(ChannelOption.SO_KEEPALIVE, true);

             ChannelFuture f = b.bind(port).sync();

             f.channel().closeFuture().sync();
         } finally {
             workerGroup.shutdownGracefully();
             bossGroup.shutdownGracefully();
         }
     }

     public static void main(String[] args) throws Exception {
         Server server = new Server();
         server.start(8000);
     }
 }

2、StringDecoder 把httpRequest转换成String，其中ByteBufToBytes是一个工具类，负责对ByteBuf中的数据进行读取

 package com.guowl.testmulticoderandhandler;

 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
 import io.netty.handler.codec.http.HttpContent;
 import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.handler.codec.http.HttpRequest;

 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 import com.guowl.utils.ByteBufToBytes;

 public class StringDecoder extends ChannelInboundHandlerAdapter {
     private static Logger   logger  = LoggerFactory.getLogger(StringDecoder.class);
     private ByteBufToBytes  reader;

     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
         logger.info("StringDecoder : msg's type is " + msg.getClass());
         if (msg instanceof HttpRequest) {
             HttpRequest request = (HttpRequest) msg;
             reader = new ByteBufToBytes((int) HttpHeaders.getContentLength(request));
         }

         if (msg instanceof HttpContent) {
             HttpContent content = (HttpContent) msg;
             reader.reading(content.content());

             if (reader.isEnd()) {
                 byte[] clientMsg = reader.readFull();
                 logger.info("StringDecoder : change httpcontent to string ");
                 ctx.fireChannelRead(new String(clientMsg));
             }
         }
     }

 }

3、BusinessHandler 具体处理业务的类，把客户端的请求打印出来，并向客户端发送信息

 package com.guowl.testmulticoderandhandler;

 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;

 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 public class BusinessHandler extends ChannelInboundHandlerAdapter {
     private Logger  logger  = LoggerFactory.getLogger(BusinessHandler.class);

     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
         String clientMsg = "client said : " + (String) msg;
         logger.info("BusinessHandler read msg from client :" + clientMsg);
         ctx.write("I am very OK!");
     }

     @Override
     public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
         ctx.flush();
     }
 }

4、StringEncoder 把字符串转换成HttpResponse

 package com.guowl.testmulticoderandhandler;

 import static io.netty.handler.codec.http.HttpHeaders.Names.CONNECTION;
 import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_LENGTH;
 import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
 import static io.netty.handler.codec.http.HttpResponseStatus.OK;
 import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;

 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelOutboundHandlerAdapter;
 import io.netty.channel.ChannelPromise;
 import io.netty.handler.codec.http.DefaultFullHttpResponse;
 import io.netty.handler.codec.http.FullHttpResponse;
 import io.netty.handler.codec.http.HttpHeaders.Values;

 // 把String转换成httpResponse
 public class StringEncoder extends ChannelOutboundHandlerAdapter {
     private Logger  logger  = LoggerFactory.getLogger(StringEncoder.class);

     @Override
     public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
         logger.info("StringEncoder response to client.");
         String serverMsg = (String) msg;

         FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer(serverMsg
                 .getBytes()));
         response.headers().set(CONTENT_TYPE, "text/plain");
         response.headers().set(CONTENT_LENGTH, response.content().readableBytes());
         response.headers().set(CONNECTION, Values.KEEP_ALIVE);
         ctx.write(response);
         ctx.flush();
     }
 }

Client端有两个类：Client ClientInitHandler
1、Client 与Server端建立连接，并向Server端发送HttpRequest请求。

 package com.guowl.testmulticoderandhandler;

 import io.netty.bootstrap.Bootstrap;
 import io.netty.buffer.Unpooled;
 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.http.DefaultFullHttpRequest;
 import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.handler.codec.http.HttpMethod;
 import io.netty.handler.codec.http.HttpRequestEncoder;
 import io.netty.handler.codec.http.HttpResponseDecoder;
 import io.netty.handler.codec.http.HttpVersion;

 import java.net.URI;

 public class Client {
     public void connect(String host, int port) throws Exception {
         EventLoopGroup workerGroup = new NioEventLoopGroup();

         try {
             Bootstrap b = new Bootstrap();
             b.group(workerGroup);
             b.channel(NioSocketChannel.class);
             b.option(ChannelOption.SO_KEEPALIVE, true);
             b.handler(new ChannelInitializer() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ch.pipeline().addLast(new HttpResponseDecoder());
                     ch.pipeline().addLast(new HttpRequestEncoder());
                     ch.pipeline().addLast(new ClientInitHandler());
                 }
             });

             // Start the client.
             ChannelFuture f = b.connect(host, port).sync();

             URI uri = new URI("http://127.0.0.1:8000");
             String msg = "Are you ok?";
             DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST,
                     uri.toASCIIString(), Unpooled.wrappedBuffer(msg.getBytes()));

             request.headers().set(HttpHeaders.Names.HOST, host);
             request.headers().set(HttpHeaders.Names.CONNECTION, HttpHeaders.Values.KEEP_ALIVE);
             request.headers().set(HttpHeaders.Names.CONTENT_LENGTH, request.content().readableBytes());
             f.channel().write(request);
             f.channel().flush();
             f.channel().closeFuture().sync();
         } finally {
             workerGroup.shutdownGracefully();
         }

     }

     public static void main(String[] args) throws Exception {
         Client client = new Client();
         client.connect("127.0.0.1", 8000);
     }
 }

2、ClientInitHandler 从Server端读取响应信息

 package com.guowl.testmulticoderandhandler;

 import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
 import io.netty.handler.codec.http.HttpContent;
 import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.handler.codec.http.HttpResponse;

 import com.guowl.utils.ByteBufToBytes;

 public class ClientInitHandler extends ChannelInboundHandlerAdapter {
     private ByteBufToBytes  reader;

     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
         if (msg instanceof HttpResponse) {
             HttpResponse response = (HttpResponse) msg;
             if (HttpHeaders.isContentLengthSet(response)) {
                 reader = new ByteBufToBytes((int) HttpHeaders.getContentLength(response));
             }
         }

         if (msg instanceof HttpContent) {
             HttpContent httpContent = (HttpContent) msg;
             ByteBuf content = httpContent.content();
             reader.reading(content);
             content.release();

             if (reader.isEnd()) {
                 String resultStr = new String(reader.readFull());
                 System.out.println("Server said:" + resultStr);
             }
         }
     }

     @Override
     public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
         ctx.close();
     }

 }

工具类：ByteBufToBytes 对ByteBuf的数据进行读取，支持流式读取（reading 和 readFull方法结合使用）
ByteBufToBytes 

 package com.guowl.utils;

 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;

 public class ByteBufToBytes {
     private ByteBuf temp;

     private boolean end = true;

     public ByteBufToBytes() {}

     public ByteBufToBytes(int length) {
         temp = Unpooled.buffer(length);
     }

     public void reading(ByteBuf datas) {
         datas.readBytes(temp, datas.readableBytes());
         if (this.temp.writableBytes() != 0) {
             end = false;
         } else {
             end = true;
         }
     }

     public boolean isEnd() {
         return end;
     }

     public byte[] readFull() {
         if (end) {
             byte[] contentByte = new byte[this.temp.readableBytes()];
             this.temp.readBytes(contentByte);
             this.temp.release();
             return contentByte;
         } else {
             return null;
         }
     }

     public byte[] read(ByteBuf datas) {
         byte[] bytes = new byte[datas.readableBytes()];
         datas.readBytes(bytes);
         return bytes;
     }
 }

运行结果：

2014-03-19 23:50:48 StringDecoder : msg's type is class io.netty.handler.codec.http.DefaultHttpRequest
2014-03-19 23:50:48 StringDecoder : msg's type is class io.netty.handler.codec.http.DefaultLastHttpContent
2014-03-19 23:50:48 StringDecoder : change httpcontent to string 
2014-03-19 23:50:48 BusinessHandler read msg from client :client said : Are you ok?
2014-03-19 23:50:48 StringEncoder response to client.

可以看到执行顺序为：StringDecoder BusinessHandler StringEncoder ，其它的都是Netty自身的，没有打印。

通过该实例证明，Encoder、Decoder的本质也是Handler，它们的执行顺序、使用方法与Handler保持一致。

执行顺序是：Encoder 先注册的后执行，与OutboundHandler一致；Decoder是先注册的先执行，与InboundHandler一致。