AsyncClientEarlyHintsEndToEnd.java
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package org.apache.hc.client5.http.examples;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import org.apache.hc.client5.http.EarlyHintsListener;
import org.apache.hc.client5.http.async.methods.SimpleHttpRequest;
import org.apache.hc.client5.http.async.methods.SimpleHttpResponse;
import org.apache.hc.client5.http.async.methods.SimpleRequestBuilder;
import org.apache.hc.client5.http.config.TlsConfig;
import org.apache.hc.client5.http.impl.async.CloseableHttpAsyncClient;
import org.apache.hc.client5.http.impl.async.HttpAsyncClients;
import org.apache.hc.client5.http.impl.nio.PoolingAsyncClientConnectionManagerBuilder;
import org.apache.hc.core5.http.ContentType;
import org.apache.hc.core5.http.EntityDetails;
import org.apache.hc.core5.http.Header;
import org.apache.hc.core5.http.HttpException;
import org.apache.hc.core5.http.HttpRequest;
import org.apache.hc.core5.http.HttpStatus;
import org.apache.hc.core5.http.URIScheme;
import org.apache.hc.core5.http.impl.BasicEntityDetails;
import org.apache.hc.core5.http.impl.bootstrap.AsyncServerBootstrap;
import org.apache.hc.core5.http.impl.bootstrap.HttpAsyncServer;
import org.apache.hc.core5.http.message.BasicHttpResponse;
import org.apache.hc.core5.http.nio.AsyncServerExchangeHandler;
import org.apache.hc.core5.http.nio.CapacityChannel;
import org.apache.hc.core5.http.nio.DataStreamChannel;
import org.apache.hc.core5.http.nio.ResponseChannel;
import org.apache.hc.core5.http.protocol.HttpContext;
import org.apache.hc.core5.io.CloseMode;
import org.apache.hc.core5.reactor.ListenerEndpoint;
/**
* Minimal end-to-end demo for {@code 103 Early Hints} using the async client.
*
* <p>This example starts a tiny local async HTTP server that:
* <ol>
* <li>sends a {@code 103} informational response with two {@code Link} headers, then</li>
* <li>completes the exchange with a final {@code 200 OK} and a short body.</li>
* </ol>
* The async client registers an Early Hints listener, prints any received {@code 103}
* headers, and then prints the final status and body.</p>
*
* <p>Use this sample to see how to wire {@code setEarlyHintsListener(...)} and verify that
* Early Hints do not interfere with normal response processing.</p>
*/
public class AsyncClientEarlyHintsEndToEnd {
public static void main(final String[] args) throws Exception {
// --- Start minimal async server that sends 103 then 200
final HttpAsyncServer server = AsyncServerBootstrap.bootstrap()
.setCanonicalHostName("localhost")
.register("/eh", () -> new AsyncServerExchangeHandler() {
private final byte[] body = "OK".getBytes(StandardCharsets.US_ASCII);
private volatile boolean sent;
@Override
public void handleRequest(final HttpRequest request,
final EntityDetails entityDetails,
final ResponseChannel channel,
final HttpContext context)
throws HttpException, IOException {
// 103 Early Hints
final BasicHttpResponse hints = new BasicHttpResponse(HttpStatus.SC_EARLY_HINTS);
hints.addHeader("Link", "</style.css>; rel=preload; as=style");
hints.addHeader("Link", "</script.js>; rel=preload; as=script");
channel.sendInformation(hints, context);
// Final 200 (announce entity; body will be produced in produce())
final BasicHttpResponse ok = new BasicHttpResponse(HttpStatus.SC_OK);
ok.addHeader("Content-Type", ContentType.TEXT_PLAIN.toString());
final BasicEntityDetails details = new BasicEntityDetails(body.length, ContentType.TEXT_PLAIN);
channel.sendResponse(ok, details, context);
}
// ---- AsyncDataConsumer (request body not expected)
@Override
public void updateCapacity(final CapacityChannel ch) throws IOException {
ch.update(Integer.MAX_VALUE);
}
@Override
public void consume(final ByteBuffer src) { /* no-op */ }
@Override
public void streamEnd(final List<? extends Header> trailers) { /* no-op */ }
// ---- AsyncDataProducer (MUST implement both of these)
@Override
public void produce(final DataStreamChannel ch) throws IOException {
if (!sent) {
ch.write(java.nio.ByteBuffer.wrap(body));
ch.endStream();
sent = true;
}
}
@Override
public int available() {
return sent ? 0 : body.length;
}
@Override
public void failed(final Exception cause) { /* no-op for demo */ }
@Override
public void releaseResources() { /* no-op for demo */ }
})
.create();
server.start();
final Future<ListenerEndpoint> lf = server.listen(new InetSocketAddress(0), URIScheme.HTTP);
final int port = ((InetSocketAddress) lf.get().getAddress()).getPort();
// --- Async client with Early Hints listener
final EarlyHintsListener hintsListener = (hints, ctx) -> {
System.out.println("[client] Early Hints 103:");
for (final Header h : hints.getHeaders("Link")) {
System.out.println(" " + h.getValue());
}
};
try (final CloseableHttpAsyncClient client = HttpAsyncClients.custom()
.setConnectionManager(
PoolingAsyncClientConnectionManagerBuilder.create()
.setDefaultTlsConfig(TlsConfig.DEFAULT) // plain HTTP here; keep TLS config for real targets
.build())
.setEarlyHintsListener(hintsListener)
.build()) {
client.start();
final SimpleHttpRequest req = SimpleRequestBuilder.get("http://localhost:" + port + "/eh").build();
final SimpleHttpResponse resp = client.execute(req, null).get(5, TimeUnit.SECONDS);
System.out.println("[client] final: " + resp.getCode() + " " + resp.getReasonPhrase());
System.out.println("[client] body: " + resp.getBodyText());
} finally {
server.close(CloseMode.GRACEFUL);
}
}
}