/*
* 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:
*
* 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.ByteBuf;
import io.netty.buffer.ByteBufHolder;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.embedded.EmbeddedChannel;
import io.netty.handler.codec.MessageToMessageCodec;
import io.netty.handler.codec.http.HttpHeaders.Names;
import io.netty.handler.codec.http.HttpHeaders.Values;
import io.netty.util.ReferenceCountUtil;
import java.util.ArrayDeque;
import java.util.List;
import java.util.Queue;
/**
* Encodes the content of the outbound {@link HttpResponse} and {@link HttpContent}.
* The original content is replaced with the new content encoded by the
* {@link EmbeddedChannel}, which is created by {@link #beginEncode(HttpResponse, String)}.
* Once encoding is finished, the value of the <tt>'Content-Encoding'</tt> header
* is set to the target content encoding, as returned by
* {@link #beginEncode(HttpResponse, String)}.
* Also, the <tt>'Content-Length'</tt> header is updated to the length of the
* encoded content. If there is no supported or allowed encoding in the
* corresponding {@link HttpRequest}'s {@code "Accept-Encoding"} header,
* {@link #beginEncode(HttpResponse, String)} should return {@code null} so that
* no encoding occurs (i.e. pass-through).
* <p>
* Please note that this is an abstract class. You have to extend this class
* and implement {@link #beginEncode(HttpResponse, String)} properly to make
* this class functional. For example, refer to the source code of
* {@link HttpContentCompressor}.
* <p>
* This handler must be placed after {@link HttpObjectEncoder} in the pipeline
* so that this handler can intercept HTTP responses before {@link HttpObjectEncoder}
* converts them into {@link ByteBuf}s.
*/
public abstract class HttpContentEncoder extends MessageToMessageCodec<HttpRequest, HttpObject> {
private enum State {
PASS_THROUGH,
AWAIT_HEADERS,
AWAIT_CONTENT
}
private final Queue<String> acceptEncodingQueue = new ArrayDeque<String>();
private String acceptEncoding;
private EmbeddedChannel encoder;
private State state = State.AWAIT_HEADERS;
@Override
public boolean acceptOutboundMessage(Object msg) throws Exception {
return msg instanceof HttpContent || msg instanceof HttpResponse;
}
@Override
protected void decode(ChannelHandlerContext ctx, HttpRequest msg, List<Object> out)
throws Exception {
String acceptedEncoding = msg.headers().get(HttpHeaders.Names.ACCEPT_ENCODING);
if (acceptedEncoding == null) {
acceptedEncoding = HttpHeaders.Values.IDENTITY;
}
acceptEncodingQueue.add(acceptedEncoding);
out.add(ReferenceCountUtil.retain(msg));
}
@Override
protected void encode(ChannelHandlerContext ctx, HttpObject msg, List<Object> out) throws Exception {
final boolean isFull = msg instanceof HttpResponse && msg instanceof LastHttpContent;
switch (state) {
case AWAIT_HEADERS: {
ensureHeaders(msg);
assert encoder == null;
final HttpResponse res = (HttpResponse) msg;
/*
* per rfc2616 4.3 Message Body
* All 1xx (informational), 204 (no content), and 304 (not modified) responses MUST NOT include a
* message-body. All other responses do include a message-body, although it MAY be of zero length.
*/
if (isPassthru(res)) {
if (isFull) {
out.add(ReferenceCountUtil.retain(res));
} else {
out.add(res);
// Pass through all following contents.
state = State.PASS_THROUGH;
}
break;
}
// Get the list of encodings accepted by the peer.
acceptEncoding = acceptEncodingQueue.poll();
if (acceptEncoding == null) {
throw new IllegalStateException("cannot send more responses than requests");
}
if (isFull) {
// Pass through the full response with empty content and continue waiting for the the next resp.
if (!((ByteBufHolder) res).content().isReadable()) {
out.add(ReferenceCountUtil.retain(res));
break;
}
}
// Prepare to encode the content.
final Result result = beginEncode(res, acceptEncoding);
// If unable to encode, pass through.
if (result == null) {
if (isFull) {
out.add(ReferenceCountUtil.retain(res));
} else {
out.add(res);
// Pass through all following contents.
state = State.PASS_THROUGH;
}
break;
}
encoder = result.contentEncoder();
// Encode the content and remove or replace the existing headers
// so that the message looks like a decoded message.
res.headers().set(Names.CONTENT_ENCODING, result.targetContentEncoding());
// Make the response chunked to simplify content transformation.
res.headers().remove(Names.CONTENT_LENGTH);
res.headers().set(Names.TRANSFER_ENCODING, Values.CHUNKED);
// Output the rewritten response.
if (isFull) {
// Convert full message into unfull one.
HttpResponse newRes = new DefaultHttpResponse(res.getProtocolVersion(), res.getStatus());
newRes.headers().set(res.headers());
out.add(newRes);
// Fall through to encode the content of the full response.
} else {
out.add(res);
state = State.AWAIT_CONTENT;
if (!(msg instanceof HttpContent)) {
// only break out the switch statement if we have not content to process
// See https://github.com/netty/netty/issues/2006
break;
}
// Fall through to encode the content
}
}
case AWAIT_CONTENT: {
ensureContent(msg);
if (encodeContent((HttpContent) msg, out)) {
state = State.AWAIT_HEADERS;
}
break;
}
case PASS_THROUGH: {
ensureContent(msg);
out.add(ReferenceCountUtil.retain(msg));
// Passed through all following contents of the current response.
if (msg instanceof LastHttpContent) {
state = State.AWAIT_HEADERS;
}
break;
}
}
}
private static boolean isPassthru(HttpResponse res) {
final int code = res.getStatus().code();
return code < 200 || code == 204 || code == 304;
}
private static void ensureHeaders(HttpObject msg) {
if (!(msg instanceof HttpResponse)) {
throw new IllegalStateException(
"unexpected message type: " +
msg.getClass().getName() + " (expected: " + HttpResponse.class.getSimpleName() + ')');
}
}
private static void ensureContent(HttpObject msg) {
if (!(msg instanceof HttpContent)) {
throw new IllegalStateException(
"unexpected message type: " +
msg.getClass().getName() + " (expected: " + HttpContent.class.getSimpleName() + ')');
}
}
private boolean encodeContent(HttpContent c, List<Object> out) {
ByteBuf content = c.content();
encode(content, out);
if (c instanceof LastHttpContent) {
finishEncode(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));
}
return true;
}
return false;
}
/**
* Prepare to encode the HTTP message content.
*
* @param headers
* the headers
* @param acceptEncoding
* the value of the {@code "Accept-Encoding"} header
*
* @return the result of preparation, which is composed of the determined
* target content encoding and a new {@link EmbeddedChannel} that
* encodes the content into the target content encoding.
* {@code null} if {@code acceptEncoding} is unsupported or rejected
* and thus the content should be handled as-is (i.e. no encoding).
*/
protected abstract Result beginEncode(HttpResponse headers, String acceptEncoding) throws Exception;
@Override
public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
cleanup();
super.handlerRemoved(ctx);
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
cleanup();
super.channelInactive(ctx);
}
private void cleanup() {
if (encoder != null) {
// Clean-up the previous encoder if not cleaned up correctly.
if (encoder.finish()) {
for (;;) {
ByteBuf buf = (ByteBuf) encoder.readOutbound();
if (buf == null) {
break;
}
// Release the buffer
// https://github.com/netty/netty/issues/1524
buf.release();
}
}
encoder = null;
}
}
private void encode(ByteBuf in, List<Object> out) {
// call retain here as it will call release after its written to the channel
encoder.writeOutbound(in.retain());
fetchEncoderOutput(out);
}
private void finishEncode(List<Object> out) {
if (encoder.finish()) {
fetchEncoderOutput(out);
}
encoder = null;
}
private void fetchEncoderOutput(List<Object> out) {
for (;;) {
ByteBuf buf = (ByteBuf) encoder.readOutbound();
if (buf == null) {
break;
}
if (!buf.isReadable()) {
buf.release();
continue;
}
out.add(new DefaultHttpContent(buf));
}
}
public static final class Result {
private final String targetContentEncoding;
private final EmbeddedChannel contentEncoder;
public Result(String targetContentEncoding, EmbeddedChannel contentEncoder) {
if (targetContentEncoding == null) {
throw new NullPointerException("targetContentEncoding");
}
if (contentEncoder == null) {
throw new NullPointerException("contentEncoder");
}
this.targetContentEncoding = targetContentEncoding;
this.contentEncoder = contentEncoder;
}
public String targetContentEncoding() {
return targetContentEncoding;
}
public EmbeddedChannel contentEncoder() {
return contentEncoder;
}
}
}