【发布时间】：2018-01-06 22:49:09
【问题描述】：
我开发了一个netty http服务器，但是当我在ChannelInboundHandlerAdapter.channelRead0方法中写响应时，我的响应结果来自另一个服务器，结果的大小是未知的，所以它的http响应头可能有内容长度或分块。所以我使用缓冲区，如果足够（读取完整数据）无论内容长度或分块，我使用内容长度，否则我使用分块。
我如何保持第一个连接的写入通道，然后将其传递给第二个处理程序以写入响应。 （我只是直接传ctx写但没有返回）
我如何有条件地决定将分块数据写入通道或具有内容长度的普通数据（如果在 channelRead0 时需要分块，添加 ChunkWriteHandler 似乎不起作用。
以一个简单的代码为例：
```java
EventLoopGroup bossGroup = new NioEventLoopGroup();
final EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap serverBootstrap = new ServerBootstrap();
serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<Channel>(){
@Override
protected void initChannel(Channel ch) throws Exception
{
System.out.println("Start, I accept client");
ChannelPipeline pipeline = ch.pipeline();
// Uncomment the following line if you want HTTPS
// SSLEngine engine =
// SecureChatSslContextFactory.getServerContext().createSSLEngine();
// engine.setUseClientMode(false);
// pipeline.addLast("ssl", new SslHandler(engine));
pipeline.addLast("decoder", new HttpRequestDecoder());
// Uncomment the following line if you don't want to handle HttpChunks.
// pipeline.addLast("aggregator", new HttpChunkAggregator(1048576));
pipeline.addLast("encoder", new HttpResponseEncoder());
// Remove the following line if you don't want automatic content
// compression.
//pipeline.addLast("aggregator", new HttpChunkAggregator(1048576));
pipeline.addLast("chunkedWriter", new ChunkedWriteHandler());
pipeline.addLast("deflater", new HttpContentCompressor());
pipeline.addLast("handler", new SimpleChannelInboundHandler<HttpObject>(){
@Override
protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception
{
System.out.println("msg=" + msg);
final ChannelHandlerContext ctxClient2Me = ctx;
// TODO: Implement this method
Bootstrap bs = new Bootstrap();
try{
//bs.resolver(new DnsAddressResolverGroup(NioDatagramChannel.class, DefaultDnsServerAddressStreamProvider.INSTANCE));
//.option(ChannelOption.TCP_NODELAY, java.lang.Boolean.TRUE)
bs.resolver(DefaultAddressResolverGroup.INSTANCE);
}catch(Exception e){
e.printStackTrace();
}
bs.channel(NioSocketChannel.class);
EventLoopGroup cg = workerGroup;//new NioEventLoopGroup();
bs.group(cg).handler(new ChannelInitializer<Channel>(){
@Override
protected void initChannel(Channel ch) throws Exception
{
System.out.println("start, server accept me");
// TODO: Implement this method
ch.pipeline().addLast("http-request-encode", new HttpRequestEncoder());
ch.pipeline().addLast(new HttpResponseDecoder());
ch.pipeline().addLast("http-res", new SimpleChannelInboundHandler<HttpObject>(){
@Override
protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception
{
// TODO: Implement this method
System.out.println("target = " + msg);
//
if(msg instanceof HttpResponse){
HttpResponse res = (HttpResponse) msg;
HttpUtil.isTransferEncodingChunked(res);
DefaultHttpResponse resClient2Me = new DefaultHttpResponse(HttpVersion.HTTP_1_1, res.getStatus());
//resClient2Me.headers().set(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
//resClient2Me.headers().set(HttpHeaderNames.CONTENT_LENGTH, "");
ctxClient2Me.write(resClient2Me);
}
if(msg instanceof LastHttpContent){
// now response the request of the client, it wastes x seconds from receiving request to response
ctxClient2Me.writeAndFlush(LastHttpContent.EMPTY_LAST_CONTENT).addListener(ChannelFutureListener.CLOSE);
ctx.close();
}else if( msg instanceof HttpContent){
//ctxClient2Me.write(new DefaultHttpContent(msg)); write chunk by chunk ?
}
}
});
System.out.println("end, server accept me");
}
});
final URI uri = new URI("http://example.com/");
String host = uri.getHost();
ChannelFuture connectFuture= bs.connect(host, 80);
System.out.println("to connect me to server");
connectFuture.addListener(new ChannelFutureListener(){
@Override
public void operationComplete(ChannelFuture cf) throws Exception
{
}
});
ChannelFuture connetedFuture = connectFuture.sync(); // TODO optimize, wait io
System.out.println("connected me to server");
DefaultFullHttpRequest req = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, uri.getRawPath());
//req.headers().set(HttpHeaderNames.HOST, "");
connetedFuture.channel().writeAndFlush(req);
System.out.println("end of Client2Me channelRead0");
System.out.println("For the seponse of Me2Server, see SimpleChannelInboundHandler.channelRead0");
}
});
System.out.println("end, I accept client");
}
});
System.out.println("========");
ChannelFuture channelFuture = serverBootstrap.bind(2080).sync();
channelFuture.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
```
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