Netty笔记（七）ChannelHandlers and Codes 整合
Netty 提供了ChannelHandler接口，还有用于Codes的ChannelHandler子接口。通过组合搭配， 灵活的构建我们需要的应用。
SSL / TSL 服务
搭建SSL/TSL，Java EE 规范提供了 SSLContext 跟 SSLEngine接口，加之Netty为我们实现了一个SSLHandler，可以容易的实现。
其过程：
示例代码：
public class SslChannelInitializer extends ChannelInitializer<Channel>
{
private final SSLContext context;
private final boolean client;
private final boolean startTls;
public SslChannelInitializer( SSLContext context, boolean client, boolean startTls )
{
this.context = context;
this.client = client;
this.startTls = startTls;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
SSLEngine engine = context.createSSLEngine();
engine.setUseClientMode( client );
ch.pipeline().addFirst( "ssl" , new SslHandler(engine, startTls));
}
}
Http 服务
实现支持Http服务，需要几个Codes
HttpRequestEncoder、HttpResponseEncoder、HttpRequestDecoder、HttpResponseDecoder
示例代码：
public class HttpDecoderEncoderInitializer extends ChannelInitializer<Channel>
{
private final boolean client;
public HttpDecoderEncoderInitializer( boolean client )
{
this.client = client;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline channelPipeline = ch.pipeline();
if ( client )
{
channelPipeline.addLast( "decoder", new HttpResponseDecoder() );
channelPipeline.addLast( "encoder", new HttpRequestEncoder() );
//or
//channelPipeline.addLast( "codes", new HttpServerCodec() );
}
else
{
channelPipeline.addLast( "decoder", new HttpRequestDecoder() );
channelPipeline.addLast( "encoder", new HttpRequestEncoder() );
//or
//channelPipeline.addLast( "codes", new HttpClientCodec() );
}
}
} 对于分段的Http信息，使用HttpObjectAggregator
public class HttpAggregatorInitializer extends ChannelInitializer<Channel>
{
private final boolean client;
public HttpAggregatorInitializer( boolean client )
{
this.client = client;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline channelPipeline = ch.pipeline();
if ( client )
{
channelPipeline.addLast( "codes", new HttpClientCodec() );
}
else
{
channelPipeline.addLast( "codes", new HttpServerCodec() );
}
/*
* if message is getting bigger , raise a TooLongFrameException is thrown
*/
channelPipeline.addLast( "aggegator", new HttpObjectAggregator( 1024 * 512 ) );
}
} 对于压缩的数据。
public class HttpCompressionInitializer extends ChannelInitializer<Channel>
{
private final boolean client;
public HttpCompressionInitializer( boolean client )
{
this.client = client;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline pipeline = ch.pipeline();
if ( client )
{
pipeline.addLast( "codes", new HttpClientCodec() );
pipeline.addLast( "decompressor", new HttpContentDecompressor() );
}
else
{
pipeline.addLast( "codes", new HttpServerCodec() );
pipeline.addLast( "compressor", new HttpContentCompressor() );
}
}
}
Https 服务。
public class HttpsCodecInitializer extends ChannelInitializer<Channel>
{
private final SSLContext context;
private final boolean client;
public HttpsCodecInitializer( SSLContext context, boolean client )
{
this.context = context;
this.client = client;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
SSLEngine engine = context.createSSLEngine();
engine.setUseClientMode( client );
ChannelPipeline pipeline = ch.pipeline();
pipeline.addFirst( "ssl", new SslHandler( engine ) );
if ( client )
{
pipeline.addLast( "codes", new HttpClientCodec() );
}
else
{
pipeline.addLast( "codes", new HttpServerCodec() );
}
}
}
处理心跳跟连接超时
IdleStateHandler ： 当连接空闲状态到达超时时间，触发事件，且事件源为IdleStateEvent
ReadTimeoutHandler ： 读数据超时，抛出ReadTimeoutException
WriteTimeoutHandler ：写数据超时，抛出WriteTimeoutException
例子代码：
public class IdleStateHandlerInitializer extends ChannelInitializer<Channel>
{
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline channelPipeline = ch.pipeline();
channelPipeline.addLast( new IdleStateHandler( 0, 0, 60, TimeUnit.SECONDS ) );
channelPipeline.addLast( new HeadbeatHandler() );
}
private static final class HeadbeatHandler extends ChannelInboundHandlerAdapter
{
private static final ByteBuf HEARTBEAT_SEQUENCE = Unpooled.unreleasableBuffer(
Unpooled.copiedBuffer( "HEARTBEAT", CharsetUtil.ISO_8859_1 ) );
@Override
public void userEventTriggered( ChannelHandlerContext ctx, Object evt ) throws Exception
{
if ( evt instanceof IdleStateEvent )
{
ctx.writeAndFlush( HEARTBEAT_SEQUENCE.duplicate() )//
.addListener( ChannelFutureListener.CLOSE_ON_FAILURE );
}
else
{
super.userEventTriggered( ctx, evt );
}
}
}
}
关于定界符的协议
DelimiterBasedFameDecoder : 根据定界符抽取数据片段的解码器
LineBasedFrameDecoder：基于行片段的解码器，用于\r\n定界符分行。
public class LineBasedHandlerInitializer extends ChannelInitializer<Channel>
{
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline channelPipeline = ch.pipeline();
channelPipeline.addLast( new LineBasedFrameDecoder( 65 * 1024 ) );
channelPipeline.addLast( new FrameHandler());
}
private static final class FrameHandler extends SimpleChannelInboundHandler<ByteBuf>
{
@Override
protected void channelRead0( ChannelHandlerContext ctx, ByteBuf msg ) throws Exception
{
// do something
}
}
} 扩展例子：
public class CmdHandlerInitializer extends ChannelInitializer<Channel>
{
private static class Cmd
{
private final ByteBuf name;
private final ByteBuf args;
public Cmd( ByteBuf name, ByteBuf args )
{
this.name = name;
this.args = args;
}
}
private static class ComDecoder extends LineBasedFrameDecoder
{
public ComDecoder( int maxLength )
{
super( maxLength );
}
@Override
protected Object decode( ChannelHandlerContext ctx, ByteBuf buffer ) throws Exception
{
ByteBuf frame = (ByteBuf) super.decode( ctx, buffer );
if ( frame == null )
{
return null;
}
int index = frame.indexOf( frame.readerIndex(), frame.writerIndex(), (byte) ' ' );
return new Cmd( frame.slice( frame.readerIndex(), index ), frame.slice( index + 1, frame.writerIndex() ) );
}
}
public static class CmdHandler extends SimpleChannelInboundHandler<Cmd>
{
@Override
protected void channelRead0( ChannelHandlerContext ctx, Cmd msg ) throws Exception
{
// do something
}
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
ch.pipeline().addLast( new ComDecoder( 65 * 1024 ) );
ch.pipeline().addLast( new CmdHandler() );
}
}
关于约定长度的协议处理
FixedLengthFrameDecoder : 抽取固定的字节长度，形成一个Frame
LengthFieldBasedFrameDecoder : 抽取信息头设置长度，划分为不同的Frame
public class LengthBasedInitializer extends ChannelInitializer<Channel>
{
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline channelPipeline = ch.pipeline();
channelPipeline.addLast( new LengthFieldBasedFrameDecoder(65*1024, 0, 8));
channelPipeline.addLast( new FrameHandler());
}
private static class FrameHandler extends SimpleChannelInboundHandler<ByteBuf>
{
@Override
protected void channelRead0( ChannelHandlerContext ctx, ByteBuf msg ) throws Exception
{
// todo something
}
}
}
写大数据
Netty允许写数据，使用 zero-memory-zero 方式。 对javaAPI进行的封装，处理了很多细节。
提供了一个分块处理的ChunkedWriterHandler
public class ChunkedWriteHandlerInitializer extends ChannelInitializer<Channel>
{
private final File file;
public ChunkedWriteHandlerInitializer( File file )
{
this.file = file;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline channelPipeline = ch.pipeline();
channelPipeline.addLast( new ChunkedWriteHandler() );
channelPipeline.addLast( new WriteStreamHandler() );
}
private class WriteStreamHandler extends ChannelInboundHandlerAdapter
{
@Override
public void channelActive( ChannelHandlerContext ctx ) throws Exception
{
super.channelActive( ctx );
ctx.writeAndFlush( new ChunkedStream(
new FileInputStream( ChunkedWriteHandlerInitializer.this.file ) ) );
}
}
}
传java对象序列化数据
使用JDK序列化，Netty提供了
CompatibleObjectDecoder、CompatibleObjectEncoder、
CompactObjectDecoder、CompactObjectEncoder
使用Jboss的Marshalling， Netty提供了
CompatibleMarshallingDecoder、CompatibleMarshallingEncoder
MarshallingDecoder、MarshallingEncoder
public class MarshallingInitializer extends ChannelInitializer<Channel>
{
private final MarshallerProvider marshallerProvider;
private final UnmarshallerProvider unmarshallerProvider;
public MarshallingInitializer( MarshallerProvider marshallerProvider, UnmarshallerProvider unmarshallerProvider )
{
this.marshallerProvider = marshallerProvider;
this.unmarshallerProvider = unmarshallerProvider;
}
@Override
protected void initChannel( Channel ch ) throws Exception
{
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast( new MarshallingDecoder( unmarshallerProvider ) );
pipeline.addLast( new MarshallingEncoder( marshallerProvider ) );
pipeline.addLast( new ObjectHandler() );
}
private static class ObjectHandler extends SimpleChannelInboundHandler<Serializable>
{
@Override
protected void channelRead0( ChannelHandlerContext ctx, Serializable msg ) throws Exception
{
// do somethod
}
}
}