HttpContentDecoder.java
/*
* Copyright 2012 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:
*
* https://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.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.handler.codec.CodecException;
import io.netty.handler.codec.DecoderResult;
import io.netty.handler.codec.MessageToMessageDecoder;
import io.netty.util.ReferenceCountUtil;
import java.util.List;
/**
* Decodes the content of the received {@link HttpRequest} and {@link HttpContent}.
* The original content is replaced with the new content decoded by the
* {@link EmbeddedChannel}, 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 HttpObjectDecoder} in the pipeline
* so that this handler can intercept HTTP requests after {@link HttpObjectDecoder}
* converts {@link ByteBuf}s into HTTP requests.
*/
public abstract class HttpContentDecoder extends MessageToMessageDecoder<HttpObject> {
static final String IDENTITY = HttpHeaderValues.IDENTITY.toString();
protected ChannelHandlerContext ctx;
private EmbeddedChannel decoder;
private boolean continueResponse;
private boolean needRead = true;
@Override
protected void decode(ChannelHandlerContext ctx, HttpObject msg, List<Object> out) throws Exception {
try {
if (msg instanceof HttpResponse && ((HttpResponse) msg).status().code() == 100) {
if (!(msg instanceof LastHttpContent)) {
continueResponse = true;
}
// 100-continue response must be passed through.
out.add(ReferenceCountUtil.retain(msg));
return;
}
if (continueResponse) {
if (msg instanceof LastHttpContent) {
continueResponse = false;
}
// 100-continue response must be passed through.
out.add(ReferenceCountUtil.retain(msg));
return;
}
if (msg instanceof HttpMessage) {
cleanup();
final HttpMessage message = (HttpMessage) msg;
final HttpHeaders headers = message.headers();
// Determine the content encoding.
String contentEncoding = headers.get(HttpHeaderNames.CONTENT_ENCODING);
if (contentEncoding != null) {
contentEncoding = contentEncoding.trim();
} else {
String transferEncoding = headers.get(HttpHeaderNames.TRANSFER_ENCODING);
if (transferEncoding != null) {
int idx = transferEncoding.indexOf(",");
if (idx != -1) {
contentEncoding = transferEncoding.substring(0, idx).trim();
} else {
contentEncoding = transferEncoding.trim();
}
} else {
contentEncoding = IDENTITY;
}
}
decoder = newContentDecoder(contentEncoding);
if (decoder == null) {
if (message instanceof HttpContent) {
((HttpContent) message).retain();
}
out.add(message);
return;
}
// Remove content-length header:
// the correct value can be set only after all chunks are processed/decoded.
// If buffering is not an issue, add HttpObjectAggregator down the chain, it will set the header.
// Otherwise, rely on LastHttpContent message.
if (headers.contains(HttpHeaderNames.CONTENT_LENGTH)) {
headers.remove(HttpHeaderNames.CONTENT_LENGTH);
headers.set(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
}
// Either it is already chunked or EOF terminated.
// See https://github.com/netty/netty/issues/5892
// set new content encoding,
CharSequence targetContentEncoding = getTargetContentEncoding(contentEncoding);
if (HttpHeaderValues.IDENTITY.contentEquals(targetContentEncoding)) {
// Do NOT set the 'Content-Encoding' header if the target encoding is 'identity'
// as per: https://tools.ietf.org/html/rfc2616#section-14.11
headers.remove(HttpHeaderNames.CONTENT_ENCODING);
} else {
headers.set(HttpHeaderNames.CONTENT_ENCODING, targetContentEncoding);
}
if (message instanceof HttpContent) {
// If message is a full request or response object (headers + data), don't copy data part into out.
// Output headers only; data part will be decoded below.
// Note: "copy" object must not be an instance of LastHttpContent class,
// as this would (erroneously) indicate the end of the HttpMessage to other handlers.
HttpMessage copy;
if (message instanceof HttpRequest) {
HttpRequest r = (HttpRequest) message; // HttpRequest or FullHttpRequest
copy = new DefaultHttpRequest(r.protocolVersion(), r.method(), r.uri());
} else if (message instanceof HttpResponse) {
HttpResponse r = (HttpResponse) message; // HttpResponse or FullHttpResponse
copy = new DefaultHttpResponse(r.protocolVersion(), r.status());
} else {
throw new CodecException("Object of class " + message.getClass().getName() +
" is not an HttpRequest or HttpResponse");
}
copy.headers().set(message.headers());
copy.setDecoderResult(message.decoderResult());
out.add(copy);
} else {
out.add(message);
}
}
if (msg instanceof HttpContent) {
final HttpContent c = (HttpContent) msg;
if (decoder == null) {
out.add(c.retain());
} else {
decodeContent(c, out);
}
}
} finally {
needRead = out.isEmpty();
}
}
private void decodeContent(HttpContent c, List<Object> out) {
ByteBuf content = c.content();
decode(content, out);
if (c instanceof LastHttpContent) {
finishDecode(out);
LastHttpContent last = (LastHttpContent) c;
// Generate an additional chunk if the decoder produced
// the last product on closure,
HttpHeaders headers = last.trailingHeaders();
if (headers.isEmpty()) {
out.add(LastHttpContent.EMPTY_LAST_CONTENT);
} else {
out.add(new ComposedLastHttpContent(headers, DecoderResult.SUCCESS));
}
}
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
boolean needRead = this.needRead;
this.needRead = true;
try {
ctx.fireChannelReadComplete();
} finally {
if (needRead && !ctx.channel().config().isAutoRead()) {
ctx.read();
}
}
}
/**
* Returns a new {@link EmbeddedChannel} 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 EmbeddedChannel} if the specified encoding is supported.
* {@code null} otherwise (alternatively, you can throw an exception
* to block unknown encoding).
*/
protected abstract EmbeddedChannel newContentDecoder(String contentEncoding) throws Exception;
/**
* Returns the expected content encoding of the decoded content.
* This getMethod 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(
@SuppressWarnings("UnusedParameters") String contentEncoding) throws Exception {
return IDENTITY;
}
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
cleanupSafely(ctx);
super.handlerRemoved(ctx);
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
cleanupSafely(ctx);
super.channelInactive(ctx);
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
this.ctx = ctx;
super.handlerAdded(ctx);
}
private void cleanup() {
if (decoder != null) {
// Clean-up the previous decoder if not cleaned up correctly.
decoder.finishAndReleaseAll();
decoder = null;
}
}
private void cleanupSafely(ChannelHandlerContext ctx) {
try {
cleanup();
} catch (Throwable cause) {
// If cleanup throws any error we need to propagate it through the pipeline
// so we don't fail to propagate pipeline events.
ctx.fireExceptionCaught(cause);
}
}
private void decode(ByteBuf in, List<Object> out) {
// call retain here as it will call release after its written to the channel
decoder.writeInbound(in.retain());
fetchDecoderOutput(out);
}
private void finishDecode(List<Object> out) {
if (decoder.finish()) {
fetchDecoderOutput(out);
}
decoder = null;
}
private void fetchDecoderOutput(List<Object> out) {
for (;;) {
ByteBuf buf = decoder.readInbound();
if (buf == null) {
break;
}
if (!buf.isReadable()) {
buf.release();
continue;
}
out.add(new DefaultHttpContent(buf));
}
}
}