我正在实现 netty 代理服务器，如下所示：
一个http请求进来，
- 如果本地缓存有数据，则写入channel并flush
- 如果没有，则从远程服务器获取数据，将其添加到缓存并刷新
我在与写入客户端的处理程序相同的处理程序中从响应中提取 byteBuf 时遇到困难。
在下面的示例中，如果您看到channelRead的方法HexDumpProxyFrontendHandler，您将看到我如何从缓存中获取并写入。我在下面的方法中添加了我遇到困难的评论
该代码端到端地工作。所以可以在本地复制和测试。
我可以看到FullHttpResponse对象在HexDumpProxyBackendhandler#channelRead。但在这个方法中，我没有对缓存的引用，也没有想要在缓存中添加的 id。
我认为有两种方法可以解决这个问题，但我不清楚如何做到这一点。
1）要么在HexdumpProxyBackendHandler中获取缓存引用和id，然后就变得容易了。但hexDumpBackendhander被实例化于channelActive of HexDumpFrontendHandler此时我还没有解析我的传入请求
2）获取响应中提取的bytebufHexdumpFrontendHandler#dchannelRead，在这种情况下它只是缓存插入。
HexDumpProxy.java
public final class HexDumpProxy {
static final int LOCAL_PORT = Integer.parseInt(System.getProperty("localPort", "8082"));
static final String REMOTE_HOST = System.getProperty("remoteHost", "api.icndb.com");
static final int REMOTE_PORT = Integer.parseInt(System.getProperty("remotePort", "80"));
static Map<Long,String> localCache = new HashMap<>();
public static void main(String[] args) throws Exception {
System.err.println("Proxying *:" + LOCAL_PORT + " to " + REMOTE_HOST + ':' + REMOTE_PORT + " ...");
localCache.put(123L, "profile1");
localCache.put(234L, "profile2");
// Configure the bootstrap.
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new HexDumpProxyInitializer(localCache, REMOTE_HOST, REMOTE_PORT))
.childOption(ChannelOption.AUTO_READ, false)
.bind(LOCAL_PORT).sync().channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
HexDumpProxyInitializer.java
public class HexDumpProxyInitializer extends ChannelInitializer<SocketChannel> {
private final String remoteHost;
private final int remotePort;
private Map<Long, String> cache;
public HexDumpProxyInitializer(Map<Long,String> cache, String remoteHost, int remotePort) {
this.remoteHost = remoteHost;
this.remotePort = remotePort;
this.cache=cache;
}
@Override
public void initChannel(SocketChannel ch) {
ch.pipeline().addLast(
new LoggingHandler(LogLevel.INFO),
new HttpServerCodec(),
new HttpObjectAggregator(8*1024, true),
new HexDumpProxyFrontendHandler(cache, remoteHost, remotePort));
}
}
HexDumpProxyFrontendHandler.java
public class HexDumpProxyFrontendHandler extends ChannelInboundHandlerAdapter {
private final String remoteHost;
private final int remotePort;
private Channel outboundChannel;
private Map<Long, String> cache;
public HexDumpProxyFrontendHandler(Map<Long, String> cache, String remoteHost, int remotePort) {
this.remoteHost = remoteHost;
this.remotePort = remotePort;
this.cache = cache;
}
@Override
public void channelActive(ChannelHandlerContext ctx) {
final Channel inboundChannel = ctx.channel();
// Start the connection attempt.
Bootstrap b = new Bootstrap();
b.group(inboundChannel.eventLoop())
.channel(ctx.channel().getClass())
.handler((new ChannelInitializer() {
protected void initChannel(Channel ch) {
ChannelPipeline var2 = ch.pipeline();
var2.addLast((new HttpClientCodec()));
var2.addLast(new HttpObjectAggregator(8192, true));
var2.addLast(new HexDumpProxyBackendHandler(inboundChannel));
}
}))
.option(ChannelOption.AUTO_READ, false);
ChannelFuture f = b.connect(remoteHost, remotePort);
outboundChannel = f.channel();
f.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
if (future.isSuccess()) {
// connection complete start to read first data
inboundChannel.read();
} else {
// Close the connection if the connection attempt has failed.
inboundChannel.close();
}
}
});
}
@Override
public void channelRead(final ChannelHandlerContext ctx, Object msg) {
if (msg instanceof HttpRequest) {
System.out.println("msg is instanceof httpRequest");
HttpRequest req = (HttpRequest)msg;
QueryStringDecoder queryStringDecoder = new QueryStringDecoder(req.uri());
String userId = queryStringDecoder.parameters().get("id").get(0);
Long id = Long.valueOf(userId);
if (cache.containsKey(id)){
StringBuilder buf = new StringBuilder();
buf.append(cache.get(id));
writeResponse(req, ctx, buf);
closeOnFlush(ctx.channel());
return;
}
}
if (outboundChannel.isActive()) {
outboundChannel.writeAndFlush(msg).addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
if (future.isSuccess()) {
// was able to flush out data, start to read the next chunk
ctx.channel().read();
} else {
future.channel().close();
}
}
});
}
//get response back from HexDumpProxyBackendHander and write to cache
//basically I need to do cache.put(id, parse(response));
//how to get response buf from inboundChannel here is the question I am trying to solve
}
@Override
public void channelInactive(ChannelHandlerContext ctx) {
if (outboundChannel != null) {
closeOnFlush(outboundChannel);
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
closeOnFlush(ctx.channel());
}
/**
* Closes the specified channel after all queued write requests are flushed.
*/
static void closeOnFlush(Channel ch) {
if (ch.isActive()) {
ch.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
}
}
//borrowed from HttpSnoopServerHandler.java in snoop example
private boolean writeResponse(HttpRequest request, ChannelHandlerContext ctx, StringBuilder buf) {
// Decide whether to close the connection or not.
boolean keepAlive = HttpUtil.isKeepAlive(request);
// Build the response object.
FullHttpResponse response = new DefaultFullHttpResponse(
HTTP_1_1, request.decoderResult().isSuccess()? OK : BAD_REQUEST,
Unpooled.copiedBuffer(buf.toString(), CharsetUtil.UTF_8));
response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain; charset=UTF-8");
if (keepAlive) {
// Add 'Content-Length' header only for a keep-alive connection.
response.headers().setInt(HttpHeaderNames.CONTENT_LENGTH, response.content().readableBytes());
// Add keep alive header as per:
// - http://www.w3.org/Protocols/HTTP/1.1/draft-ietf-http-v11-spec-01.html#Connection
response.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
}
// Encode the cookie.
String cookieString = request.headers().get(HttpHeaderNames.COOKIE);
if (cookieString != null) {
Set<Cookie> cookies = ServerCookieDecoder.STRICT.decode(cookieString);
if (!cookies.isEmpty()) {
// Reset the cookies if necessary.
for (io.netty.handler.codec.http.cookie.Cookie cookie: cookies) {
response.headers().add(HttpHeaderNames.SET_COOKIE, io.netty.handler.codec.http.cookie.ServerCookieEncoder.STRICT.encode(cookie));
}
}
} else {
// Browser sent no cookie. Add some.
response.headers().add(HttpHeaderNames.SET_COOKIE, io.netty.handler.codec.http.cookie.ServerCookieEncoder.STRICT.encode("key1", "value1"));
response.headers().add(HttpHeaderNames.SET_COOKIE, ServerCookieEncoder.STRICT.encode("key2", "value2"));
}
// Write the response.
ctx.write(response);
return keepAlive;
}
}
HexDumpProxyBackendHandler.java
public class HexDumpProxyBackendHandler extends ChannelInboundHandlerAdapter {
private final Channel inboundChannel;
public HexDumpProxyBackendHandler(Channel inboundChannel) {
this.inboundChannel = inboundChannel;
}
@Override
public void channelActive(ChannelHandlerContext ctx) {
ctx.read();
}
@Override
public void channelRead(final ChannelHandlerContext ctx, Object msg) {
if (msg instanceof FullHttpResponse) {
System.out.println("this is fullHttpResponse");
}
inboundChannel.writeAndFlush(msg).addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
if (future.isSuccess()) {
ctx.channel().read();
} else {
future.channel().close();
}
}
});
}
@Override
public void channelInactive(ChannelHandlerContext ctx) {
HexDumpProxyFrontendHandler.closeOnFlush(inboundChannel);
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
HexDumpProxyFrontendHandler.closeOnFlush(ctx.channel());
}
}
P.S：我从以下位置获取了大部分代码Netty 示例 https://github.com/netty/netty/tree/4.1/example/src/main/java/io/netty/example/proxy项目并定制
EDIT
根据 Ferrygig 的建议，我将 FrontEndChannelHander#channelRead 更改如下。我已经删除了channelActive并实现了写入方法
@覆盖
公共无效channelRead（最终ChannelHandlerContext ctx，对象消息）{
if (msg instanceof HttpRequest) {
System.out.println("msg is instanceof httpRequest");
HttpRequest req = (HttpRequest)msg;
QueryStringDecoder queryStringDecoder = new QueryStringDecoder(req.uri());
String userId = queryStringDecoder.parameters().get("id").get(0);
id = Long.valueOf(userId);
if (cache.containsKey(id)){
StringBuilder buf = new StringBuilder();
buf.append(cache.get(id));
writeResponse(req, ctx, buf);
closeOnFlush(ctx.channel());
return;
}
final Channel inboundChannel = ctx.channel();
//copied from channelActive method
// Start the connection attempt.
Bootstrap b = new Bootstrap();
b.group(inboundChannel.eventLoop())
.channel(ctx.channel().getClass())
.handler((new ChannelInitializer() {
protected void initChannel(Channel ch) {
ChannelPipeline var2 = ch.pipeline();
var2.addLast((new HttpClientCodec()));
var2.addLast(new HttpObjectAggregator(8192, true));
var2.addLast(new HexDumpProxyBackendHandler(inboundChannel, cache));
}
}));
//.option(ChannelOption.AUTO_READ, false);
ChannelFuture f = b.connect(remoteHost, remotePort);
outboundChannel = f.channel();
f.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
if (future.isSuccess()) {
// connection complete start to read first data
inboundChannel.read();
} else {
// Close the connection if the connection attempt has failed.
inboundChannel.close();
}
}
});
}
if (outboundChannel.isActive()) {
outboundChannel.writeAndFlush(msg).addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) {
if (future.isSuccess()) {
// was able to flush out data, start to read the next chunk
ctx.channel().read();
} else {
future.channel().close();
}
}
});
}
