Netty4.0学习笔记系列之四：混合使用coder和handler

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：

[java] view
plain copy







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<SocketChannel>() {

@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

[java] view
plain copy







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

[java] view
plain copy







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

[java] view
plain copy







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。

[java] view
plain copy







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<SocketChannel>() {

@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

[java] view
plain copy







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

[java] view
plain copy







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。