org.jboss.netty.handler.codec.http
Class HttpMessageDecoder

java.lang.Object
  org.jboss.netty.channel.SimpleChannelUpstreamHandler
      org.jboss.netty.handler.codec.replay.ReplayingDecoder<HttpMessageDecoder.State>
          org.jboss.netty.handler.codec.http.HttpMessageDecoder

All Implemented Interfaces:

ChannelHandler, ChannelUpstreamHandler

Direct Known Subclasses:

HttpRequestDecoder, HttpResponseDecoder, RtspMessageDecoder

public abstract class HttpMessageDecoder
extends ReplayingDecoder<HttpMessageDecoder.State>

Decodes ChannelBuffers into HttpMessages and HttpChunks.

Parameters that prevents excessive memory consumption

Name	Meaning
maxInitialLineLength	The maximum length of the initial line (e.g. "GET / HTTP/1.0" or "HTTP/1.0 200 OK") If the length of the initial line exceeds this value, a TooLongFrameException will be raised.
maxHeaderSize	The maximum length of all headers. If the sum of the length of each header exceeds this value, a TooLongFrameException will be raised.
maxChunkSize	The maximum length of the content or each chunk. If the content length (or the length of each chunk) exceeds this value, the content or chunk will be split into multiple HttpChunks whose length is maxChunkSize at maximum.

Chunked Content

If the content of an HTTP message is greater than maxChunkSize or the transfer encoding of the HTTP message is 'chunked', this decoder generates one HttpMessage instance and its following HttpChunks per single HTTP message to avoid excessive memory consumption. For example, the following HTTP message:

 GET / HTTP/1.1
 Transfer-Encoding: chunked

 1a
 abcdefghijklmnopqrstuvwxyz
 10
 1234567890abcdef
 0
 Content-MD5: ...
 [blank line]
 

triggers HttpRequestDecoder to generate 4 objects:

1. An HttpRequest whose chunked property is true,
2. The first HttpChunk whose content is 'abcdefghijklmnopqrstuvwxyz',
3. The second HttpChunk whose content is '1234567890abcdef', and
4. An HttpChunkTrailer which marks the end of the content.

If you prefer not to handle HttpChunks by yourself for your convenience, insert HttpChunkAggregator after this decoder in the ChannelPipeline. However, please note that your server might not be as memory efficient as without the aggregator.

Extensibility

Please note that this decoder is designed to be extended to implement a protocol derived from HTTP, such as RTSP and ICAP. To implement the decoder of such a derived protocol, extend this class and implement all abstract methods properly.

Version:

$Rev: 2370 $, $Date: 2010-10-19 14:40:44 +0900 (Tue, 19 Oct 2010) $

Author:

The Netty Project, Andy Taylor (andy.taylor@jboss.org), Trustin Lee

Nested Class Summary

protected static class

HttpMessageDecoder.State The internal state of HttpMessageDecoder.

Nested classes/interfaces inherited from interface org.jboss.netty.channel.ChannelHandler

ChannelHandler.Sharable

Constructor Summary

protected	HttpMessageDecoder() Creates a new instance with the default maxInitialLineLength (4096}, maxHeaderSize (8192), and maxChunkSize (8192).
protected	HttpMessageDecoder(int maxInitialLineLength, int maxHeaderSize, int maxChunkSize) Creates a new instance with the specified parameters.

Method Summary

protected abstract HttpMessage	createMessage(String[] initialLine)
protected Object	decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer, HttpMessageDecoder.State state) Decodes the received packets so far into a frame.
protected boolean	isContentAlwaysEmpty(HttpMessage msg)
protected abstract boolean	isDecodingRequest()

Methods inherited from class org.jboss.netty.handler.codec.replay.ReplayingDecoder

actualReadableBytes, channelClosed, channelDisconnected, checkpoint, checkpoint, decodeLast, exceptionCaught, getState, internalBuffer, messageReceived, setState

Methods inherited from class org.jboss.netty.channel.SimpleChannelUpstreamHandler

channelBound, channelConnected, channelInterestChanged, channelOpen, channelUnbound, childChannelClosed, childChannelOpen, handleUpstream, writeComplete

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HttpMessageDecoder

protected HttpMessageDecoder()

Creates a new instance with the default maxInitialLineLength (4096}, maxHeaderSize (8192), and maxChunkSize (8192).

HttpMessageDecoder

protected HttpMessageDecoder(int maxInitialLineLength,
                             int maxHeaderSize,
                             int maxChunkSize)

Creates a new instance with the specified parameters.

Method Detail

decode

protected Object decode(ChannelHandlerContext ctx,
                        Channel channel,
                        ChannelBuffer buffer,
                        HttpMessageDecoder.State state)
                 throws Exception

Description copied from class: ReplayingDecoder

Decodes the received packets so far into a frame.

Specified by:

decode in class ReplayingDecoder<HttpMessageDecoder.State>

Parameters:

ctx - the context of this handler

channel - the current channel

buffer - the cumulative buffer of received packets so far. Note that the buffer might be empty, which means you should not make an assumption that the buffer contains at least one byte in your decoder implementation.

state - the current decoder state (null if unused)

Returns:

the decoded frame

Throws:

Exception

isContentAlwaysEmpty

protected boolean isContentAlwaysEmpty(HttpMessage msg)

isDecodingRequest

protected abstract boolean isDecodingRequest()

createMessage

protected abstract HttpMessage createMessage(String[] initialLine)
                                      throws Exception

Throws:

Exception