Add a HTTP/2 client example using the newer frames approach the current HTTP/2 client example uses the older 'HTTP/1 <--> HTTP/2' translation approach. (#10081)
**Motivation:** When I was previously working on a project using Netty's HTTP/2 support, I used the newer frames approach but I struggled to find any good examples or documentation online. I did, however, see a few people ask the same (or similar) questions as me on StackOverflow and a couple of older Netty Github issues. Reading issue [9733](https://github.com/netty/netty/issues/9733) therefore prompted me to pull together a few bits of code into this HTTP/2 frame client example. **Modification:** Populated the previously-empty `example/src/main/java/io/netty/example/http2/helloworld/frame/client/` folder with a HTTP/2 frame client example. **Result:** Gives a clear example of how the newer HTTP/2 support can be used for Netty clients.
This commit is contained in:
Tristan Perry
GitHub
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@ -50,9 +50,13 @@ import static io.netty.handler.codec.http.HttpMethod.POST;
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import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;
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/**
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* An HTTP2 client that allows you to send HTTP2 frames to a server. Inbound and outbound frames are
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* logged. When run from the command-line, sends a single HEADERS frame to the server and gets back
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* An HTTP2 client that allows you to send HTTP2 frames to a server using HTTP1-style approaches
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* (via {@link io.netty.handler.codec.http2.InboundHttp2ToHttpAdapter}). Inbound and outbound
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* frames are logged.
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* When run from the command-line, sends a single HEADERS frame to the server and gets back
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* a "Hello World" response.
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* See the ./http2/helloworld/frame/client/ example for a HTTP2 client example which does not use
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* HTTP1-style objects and patterns.
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*/
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public final class Http2Client {
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@ -0,0 +1,57 @@
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/*
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* Copyright 2020 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License, version 2.0 (the
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* "License"); you may not use this file except in compliance with the License. You may obtain a
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* copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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package io.netty.example.http2.helloworld.frame.client;
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import io.netty.channel.Channel;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.ChannelInitializer;
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import io.netty.channel.SimpleChannelInboundHandler;
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import io.netty.handler.codec.http2.Http2FrameCodec;
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import io.netty.handler.codec.http2.Http2FrameCodecBuilder;
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import io.netty.handler.codec.http2.Http2MultiplexHandler;
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import io.netty.handler.codec.http2.Http2Settings;
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import io.netty.handler.ssl.SslContext;
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/**
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* Configures client pipeline to support HTTP/2 frames via {@link Http2FrameCodec} and {@link Http2MultiplexHandler}.
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*/
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public final class Http2ClientFrameInitializer extends ChannelInitializer<Channel> {
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private final SslContext sslCtx;
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public Http2ClientFrameInitializer(SslContext sslCtx) {
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this.sslCtx = sslCtx;
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}
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@Override
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protected void initChannel(Channel ch) throws Exception {
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// ensure that our 'trust all' SSL handler is the first in the pipeline if SSL is enabled.
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if (sslCtx != null) {
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ch.pipeline().addFirst(sslCtx.newHandler(ch.alloc()));
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}
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final Http2FrameCodec http2FrameCodec = Http2FrameCodecBuilder.forClient()
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.initialSettings(Http2Settings.defaultSettings()) // this is the default, but shows it can be changed.
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.build();
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ch.pipeline().addLast(http2FrameCodec);
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ch.pipeline().addLast(new Http2MultiplexHandler(new SimpleChannelInboundHandler() {
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@Override
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protected void channelRead0(ChannelHandlerContext ctx, Object msg) {
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// NOOP (this is the handler for 'inbound' streams, which is not relevant in this example)
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}
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}));
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}
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}
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@ -0,0 +1,61 @@
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/*
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* Copyright 2020 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License, version 2.0 (the
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* "License"); you may not use this file except in compliance with the License. You may obtain a
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* copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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package io.netty.example.http2.helloworld.frame.client;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.SimpleChannelInboundHandler;
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import io.netty.handler.codec.http2.Http2DataFrame;
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import io.netty.handler.codec.http2.Http2HeadersFrame;
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import io.netty.handler.codec.http2.Http2StreamFrame;
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import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.TimeUnit;
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/**
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* Handles HTTP/2 stream frame responses. This is a useful approach if you specifically want to check
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* the main HTTP/2 response DATA/HEADERs, but in this example it's used purely to see whether
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* our request (for a specific stream id) has had a final response (for that same stream id).
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*/
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public final class Http2ClientStreamFrameResponseHandler extends SimpleChannelInboundHandler<Http2StreamFrame> {
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private final CountDownLatch latch = new CountDownLatch(1);
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@Override
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protected void channelRead0(ChannelHandlerContext ctx, Http2StreamFrame msg) throws Exception {
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System.out.println("Received HTTP/2 'stream' frame: " + msg);
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// isEndStream() is not from a common interface, so we currently must check both
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if (msg instanceof Http2DataFrame && ((Http2DataFrame) msg).isEndStream()) {
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latch.countDown();
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} else if (msg instanceof Http2HeadersFrame && ((Http2HeadersFrame) msg).isEndStream()) {
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latch.countDown();
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}
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}
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/**
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* Waits for the latch to be decremented (i.e. for an end of stream message to be received), or for
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* the latch to expire after 5 seconds.
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* @return true if a successful HTTP/2 end of stream message was received.
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*/
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public boolean responseSuccessfullyCompleted() {
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try {
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return latch.await(5, TimeUnit.SECONDS);
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} catch (InterruptedException ie) {
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System.err.println("Latch exception: " + ie.getMessage());
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return false;
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}
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}
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}
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@ -0,0 +1,124 @@
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/*
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* Copyright 2020 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License, version 2.0 (the
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* "License"); you may not use this file except in compliance with the License. You may obtain a
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* copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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package io.netty.example.http2.helloworld.frame.client;
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import io.netty.bootstrap.Bootstrap;
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import io.netty.channel.Channel;
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import io.netty.channel.ChannelOption;
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import io.netty.channel.EventLoopGroup;
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import io.netty.channel.nio.NioEventLoopGroup;
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import io.netty.channel.socket.nio.NioSocketChannel;
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import io.netty.handler.codec.http2.DefaultHttp2Headers;
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import io.netty.handler.codec.http2.DefaultHttp2HeadersFrame;
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import io.netty.handler.codec.http2.Http2HeadersFrame;
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import io.netty.handler.codec.http2.Http2SecurityUtil;
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import io.netty.handler.codec.http2.Http2StreamChannel;
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import io.netty.handler.codec.http2.Http2StreamChannelBootstrap;
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import io.netty.handler.ssl.ApplicationProtocolConfig;
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import io.netty.handler.ssl.ApplicationProtocolConfig.Protocol;
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import io.netty.handler.ssl.ApplicationProtocolConfig.SelectedListenerFailureBehavior;
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import io.netty.handler.ssl.ApplicationProtocolConfig.SelectorFailureBehavior;
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import io.netty.handler.ssl.ApplicationProtocolNames;
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import io.netty.handler.ssl.SslContext;
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import io.netty.handler.ssl.SslContextBuilder;
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import io.netty.handler.ssl.SslProvider;
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import io.netty.handler.ssl.SupportedCipherSuiteFilter;
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import io.netty.handler.ssl.util.InsecureTrustManagerFactory;
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/**
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* An HTTP2 client that allows you to send HTTP2 frames to a server using the newer HTTP2
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* approach (via {@link io.netty.handler.codec.http2.Http2FrameCodec}).
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* When run from the command-line, sends a single HEADERS frame (with prior knowledge) to
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* the server configured at host:port/path.
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* You should include {@link io.netty.handler.codec.http2.Http2ClientUpgradeCodec} if the
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* HTTP/2 server you are hitting doesn't support h2c/prior knowledge.
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*/
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public final class Http2FrameClient {
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static final boolean SSL = System.getProperty("ssl") != null;
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static final String HOST = System.getProperty("host", "127.0.0.1");
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static final int PORT = Integer.parseInt(System.getProperty("port", SSL? "8443" : "8080"));
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static final String PATH = System.getProperty("path", "/");
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private Http2FrameClient() {
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}
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public static void main(String[] args) throws Exception {
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final EventLoopGroup clientWorkerGroup = new NioEventLoopGroup();
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// Configure SSL.
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final SslContext sslCtx;
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if (SSL) {
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final SslProvider provider =
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SslProvider.isAlpnSupported(SslProvider.OPENSSL)? SslProvider.OPENSSL : SslProvider.JDK;
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sslCtx = SslContextBuilder.forClient()
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.sslProvider(provider)
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.ciphers(Http2SecurityUtil.CIPHERS, SupportedCipherSuiteFilter.INSTANCE)
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// you probably won't want to use this in production, but it is fine for this example:
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.trustManager(InsecureTrustManagerFactory.INSTANCE)
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.applicationProtocolConfig(new ApplicationProtocolConfig(
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Protocol.ALPN,
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SelectorFailureBehavior.NO_ADVERTISE,
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SelectedListenerFailureBehavior.ACCEPT,
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ApplicationProtocolNames.HTTP_2,
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ApplicationProtocolNames.HTTP_1_1))
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.build();
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} else {
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sslCtx = null;
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}
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try {
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final Bootstrap b = new Bootstrap();
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b.group(clientWorkerGroup);
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b.channel(NioSocketChannel.class);
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b.option(ChannelOption.SO_KEEPALIVE, true);
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b.remoteAddress(HOST, PORT);
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b.handler(new Http2ClientFrameInitializer(sslCtx));
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// Start the client.
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final Channel channel = b.connect().syncUninterruptibly().channel();
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System.out.println("Connected to [" + HOST + ':' + PORT + ']');
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final Http2ClientStreamFrameResponseHandler streamFrameResponseHandler =
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new Http2ClientStreamFrameResponseHandler();
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final Http2StreamChannelBootstrap streamChannelBootstrap = new Http2StreamChannelBootstrap(channel);
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final Http2StreamChannel streamChannel = streamChannelBootstrap.open().syncUninterruptibly().getNow();
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streamChannel.pipeline().addLast(streamFrameResponseHandler);
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// Send request (a HTTP/2 HEADERS frame - with ':method = GET' in this case)
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final DefaultHttp2Headers headers = new DefaultHttp2Headers();
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headers.method("GET");
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headers.path(PATH);
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headers.scheme(SSL? "https" : "http");
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final Http2HeadersFrame headersFrame = new DefaultHttp2HeadersFrame(headers);
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streamChannel.writeAndFlush(headersFrame);
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System.out.println("Sent HTTP/2 GET request to " + PATH);
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// Wait for the responses (or for the latch to expire), then clean up the connections
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if (!streamFrameResponseHandler.responseSuccessfullyCompleted()) {
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System.err.println("Did not get HTTP/2 response in expected time.");
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}
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System.out.println("Finished HTTP/2 request, will close the connection.");
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// Wait until the connection is closed.
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channel.close().syncUninterruptibly();
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} finally {
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clientWorkerGroup.shutdownGracefully();
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}
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}
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}
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