/*
* Copyright 2011 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.handler.codec.http;
import io.netty.buffer.ChannelBuffer;
import io.netty.buffer.ChannelBuffers;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.Channels;
import io.netty.channel.MessageEvent;
import io.netty.channel.SimpleChannelUpstreamHandler;
import io.netty.handler.codec.embedder.DecoderEmbedder;
/**
* Decodes the content of the received {@link HttpRequest} and {@link HttpChunk}.
* The original content is replaced with the new content decoded by the
* {@link DecoderEmbedder}, which is created by {@link #newContentDecoder(String)}.
* Once decoding is finished, the value of the <tt>'Content-Encoding'</tt>
* header is set to the target content encoding, as returned by {@link #getTargetContentEncoding(String)}.
* Also, the <tt>'Content-Length'</tt> header is updated to the length of the
* decoded content. If the content encoding of the original is not supported
* by the decoder, {@link #newContentDecoder(String)} should return {@code null}
* so that no decoding occurs (i.e. pass-through).
* <p>
* Please note that this is an abstract class. You have to extend this class
* and implement {@link #newContentDecoder(String)} properly to make this class
* functional. For example, refer to the source code of {@link HttpContentDecompressor}.
* <p>
* This handler must be placed after {@link HttpMessageDecoder} in the pipeline
* so that this handler can intercept HTTP requests after {@link HttpMessageDecoder}
* converts {@link ChannelBuffer}s into HTTP requests.
*/
public abstract class HttpContentDecoder extends SimpleChannelUpstreamHandler {
private DecoderEmbedder<ChannelBuffer> decoder;
/**
* Creates a new instance.
*/
protected HttpContentDecoder() {
}
@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
Object msg = e.getMessage();
if (msg instanceof HttpResponse && ((HttpResponse) msg).getStatus().getCode() == 100) {
// 100-continue response must be passed through.
ctx.sendUpstream(e);
} else if (msg instanceof HttpMessage) {
HttpMessage m = (HttpMessage) msg;
decoder = null;
// Determine the content encoding.
String contentEncoding = m.getHeader(HttpHeaders.Names.CONTENT_ENCODING);
if (contentEncoding != null) {
contentEncoding = contentEncoding.trim();
} else {
contentEncoding = HttpHeaders.Values.IDENTITY;
}
boolean hasContent = m.isChunked() || m.getContent().readable();
if (hasContent && (decoder = newContentDecoder(contentEncoding)) != null) {
// Decode the content and remove or replace the existing headers
// so that the message looks like a decoded message.
m.setHeader(
HttpHeaders.Names.CONTENT_ENCODING,
getTargetContentEncoding(contentEncoding));
if (!m.isChunked()) {
ChannelBuffer content = m.getContent();
// Decode the content
content = ChannelBuffers.wrappedBuffer(
decode(content), finishDecode());
// Replace the content.
m.setContent(content);
if (m.containsHeader(HttpHeaders.Names.CONTENT_LENGTH)) {
m.setHeader(
HttpHeaders.Names.CONTENT_LENGTH,
Integer.toString(content.readableBytes()));
}
}
}
// Because HttpMessage is a mutable object, we can simply forward the received event.
ctx.sendUpstream(e);
} else if (msg instanceof HttpChunk) {
HttpChunk c = (HttpChunk) msg;
ChannelBuffer content = c.getContent();
// Decode the chunk if necessary.
if (decoder != null) {
if (!c.isLast()) {
content = decode(content);
if (content.readable()) {
c.setContent(content);
ctx.sendUpstream(e);
}
} else {
ChannelBuffer lastProduct = finishDecode();
// Generate an additional chunk if the decoder produced
// the last product on closure,
if (lastProduct.readable()) {
Channels.fireMessageReceived(
ctx, new DefaultHttpChunk(lastProduct), e.getRemoteAddress());
}
// Emit the last chunk.
ctx.sendUpstream(e);
}
} else {
ctx.sendUpstream(e);
}
} else {
ctx.sendUpstream(e);
}
}
/**
* Returns a new {@link DecoderEmbedder} that decodes the HTTP message
* content encoded in the specified <tt>contentEncoding</tt>.
*
* @param contentEncoding the value of the {@code "Content-Encoding"} header
* @return a new {@link DecoderEmbedder} if the specified encoding is supported.
* {@code null} otherwise (alternatively, you can throw an exception
* to block unknown encoding).
*/
protected abstract DecoderEmbedder<ChannelBuffer> newContentDecoder(String contentEncoding) throws Exception;
/**
* Returns the expected content encoding of the decoded content.
* This method returns {@code "identity"} by default, which is the case for
* most decoders.
*
* @param contentEncoding the value of the {@code "Content-Encoding"} header
* @return the expected content encoding of the new content
*/
protected String getTargetContentEncoding(String contentEncoding) throws Exception {
return HttpHeaders.Values.IDENTITY;
}
private ChannelBuffer decode(ChannelBuffer buf) {
decoder.offer(buf);
return ChannelBuffers.wrappedBuffer(decoder.pollAll(new ChannelBuffer[decoder.size()]));
}
private ChannelBuffer finishDecode() {
ChannelBuffer result;
if (decoder.finish()) {
result = ChannelBuffers.wrappedBuffer(decoder.pollAll(new ChannelBuffer[decoder.size()]));
} else {
result = ChannelBuffers.EMPTY_BUFFER;
}
decoder = null;
return result;
}
}