360 lines
14 KiB
Java
360 lines
14 KiB
Java
/*
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* Copyright (c) 2016, 2023, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.io.Reader;
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import java.net.URI;
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import java.net.http.HttpClient;
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import java.net.http.HttpHeaders;
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import java.net.http.HttpRequest;
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import java.net.http.HttpResponse;
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import java.nio.ByteBuffer;
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import java.nio.charset.Charset;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Locale;
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import java.util.Optional;
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import java.util.concurrent.ArrayBlockingQueue;
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import java.util.concurrent.BlockingQueue;
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import java.util.concurrent.CompletableFuture;
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import java.util.concurrent.CompletionStage;
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import java.util.concurrent.Flow;
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import java.util.stream.Stream;
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import static java.lang.System.err;
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/*
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* @test
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* @summary An example on how to read a response body with InputStream.
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* @run main/othervm/manual -Dtest.debug=true HttpInputStreamTest
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* @author daniel fuchs
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*/
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public class HttpInputStreamTest {
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public static boolean DEBUG = Boolean.getBoolean("test.debug");
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/**
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* A simple HttpResponse.BodyHandler that creates a live
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* InputStream to read the response body from the underlying ByteBuffer
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* Flow.
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* The InputStream is made immediately available for consumption, before
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* the response body is fully received.
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*/
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public static class HttpInputStreamHandler
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implements HttpResponse.BodyHandler<InputStream> {
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public static final int MAX_BUFFERS_IN_QUEUE = 1; // lock-step with the producer
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private final int maxBuffers;
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public HttpInputStreamHandler() {
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this(MAX_BUFFERS_IN_QUEUE);
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}
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public HttpInputStreamHandler(int maxBuffers) {
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this.maxBuffers = maxBuffers <= 0 ? MAX_BUFFERS_IN_QUEUE : maxBuffers;
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}
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@Override
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public HttpResponse.BodySubscriber<InputStream>
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apply(HttpResponse.ResponseInfo rinfo) {
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return new HttpResponseInputStream(maxBuffers);
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}
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/**
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* An InputStream built on top of the Flow API.
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*/
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private static class HttpResponseInputStream extends InputStream
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implements HttpResponse.BodySubscriber<InputStream> {
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// An immutable ByteBuffer sentinel to mark that the last byte was received.
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private static final ByteBuffer LAST_BUFFER = ByteBuffer.wrap(new byte[0]);
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private static final List<ByteBuffer> LAST_LIST = List.of(LAST_BUFFER);
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// A queue of yet unprocessed ByteBuffers received from the flow API.
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private final BlockingQueue<List<ByteBuffer>> buffers;
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private volatile Flow.Subscription subscription;
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private volatile boolean closed;
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private volatile Throwable failed;
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private volatile Iterator<ByteBuffer> currentListItr;
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private volatile ByteBuffer currentBuffer;
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HttpResponseInputStream() {
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this(MAX_BUFFERS_IN_QUEUE);
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}
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HttpResponseInputStream(int maxBuffers) {
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int capacity = maxBuffers <= 0 ? MAX_BUFFERS_IN_QUEUE : maxBuffers;
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// 1 additional slot for LAST_LIST added by onComplete
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this.buffers = new ArrayBlockingQueue<>(capacity + 1);
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}
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@Override
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public CompletionStage<InputStream> getBody() {
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// Return the stream immediately, before the
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// response body is received.
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// This makes it possible for senAsync().get().body()
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// to complete before the response body is received.
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return CompletableFuture.completedStage(this);
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}
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// Returns the current byte buffer to read from.
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// If the current buffer has no remaining data, will take the
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// next buffer from the buffers queue, possibly blocking until
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// a new buffer is made available through the Flow API, or the
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// end of the flow is reached.
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private ByteBuffer current() throws IOException {
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while (currentBuffer == null || !currentBuffer.hasRemaining()) {
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// Check whether the stream is closed or exhausted
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if (closed || failed != null) {
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throw new IOException("closed", failed);
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}
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if (currentBuffer == LAST_BUFFER) break;
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try {
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if (currentListItr == null || !currentListItr.hasNext()) {
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// Take a new list of buffers from the queue, blocking
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// if none is available yet...
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if (DEBUG) err.println("Taking list of Buffers");
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List<ByteBuffer> lb = buffers.take();
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currentListItr = lb.iterator();
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if (DEBUG) err.println("List of Buffers Taken");
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// Check whether an exception was encountered upstream
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if (closed || failed != null)
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throw new IOException("closed", failed);
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// Check whether we're done.
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if (lb == LAST_LIST) {
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currentListItr = null;
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currentBuffer = LAST_BUFFER;
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break;
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}
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// Request another upstream item ( list of buffers )
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Flow.Subscription s = subscription;
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if (s != null)
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s.request(1);
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}
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assert currentListItr != null;
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assert currentListItr.hasNext();
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if (DEBUG) err.println("Next Buffer");
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currentBuffer = currentListItr.next();
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} catch (InterruptedException ex) {
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// continue
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}
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}
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assert currentBuffer == LAST_BUFFER || currentBuffer.hasRemaining();
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return currentBuffer;
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}
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@Override
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public int read(byte[] bytes, int off, int len) throws IOException {
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// get the buffer to read from, possibly blocking if
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// none is available
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ByteBuffer buffer;
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if ((buffer = current()) == LAST_BUFFER) return -1;
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// don't attempt to read more than what is available
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// in the current buffer.
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int read = Math.min(buffer.remaining(), len);
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assert read > 0 && read <= buffer.remaining();
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// buffer.get() will do the boundary check for us.
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buffer.get(bytes, off, read);
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return read;
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}
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@Override
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public int read() throws IOException {
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ByteBuffer buffer;
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if ((buffer = current()) == LAST_BUFFER) return -1;
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return buffer.get() & 0xFF;
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}
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@Override
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public void onSubscribe(Flow.Subscription s) {
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if (this.subscription != null) {
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s.cancel();
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return;
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}
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this.subscription = s;
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assert buffers.remainingCapacity() > 1; // should at least be 2
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if (DEBUG) err.println("onSubscribe: requesting "
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+ Math.max(1, buffers.remainingCapacity() - 1));
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s.request(Math.max(1, buffers.remainingCapacity() - 1));
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}
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@Override
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public void onNext(List<ByteBuffer> t) {
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try {
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if (DEBUG) err.println("next item received");
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if (!buffers.offer(t)) {
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throw new IllegalStateException("queue is full");
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}
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if (DEBUG) err.println("item offered");
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} catch (Exception ex) {
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failed = ex;
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try {
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close();
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} catch (IOException ex1) {
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// OK
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}
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}
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}
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@Override
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public void onError(Throwable thrwbl) {
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subscription = null;
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failed = thrwbl;
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}
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@Override
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public void onComplete() {
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subscription = null;
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onNext(LAST_LIST);
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}
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@Override
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public void close() throws IOException {
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synchronized (this) {
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if (closed) return;
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closed = true;
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}
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Flow.Subscription s = subscription;
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subscription = null;
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if (s != null) {
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s.cancel();
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}
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super.close();
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}
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}
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}
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/**
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* Examine the response headers to figure out the charset used to
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* encode the body content.
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* If the content type is not textual, returns an empty Optional.
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* Otherwise, returns the body content's charset, defaulting to
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* ISO-8859-1 if none is explicitly specified.
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* @param headers The response headers.
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* @return The charset to use for decoding the response body, if
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* the response body content is text/...
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*/
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public static Optional<Charset> getCharset(HttpHeaders headers) {
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Optional<String> contentType = headers.firstValue("Content-Type");
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Optional<Charset> charset = Optional.empty();
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if (contentType.isPresent()) {
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final String[] values = contentType.get().split(";");
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if (values[0].startsWith("text/")) {
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charset = Optional.of(Stream.of(values)
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.map(x -> x.toLowerCase(Locale.ROOT))
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.map(String::trim)
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.filter(x -> x.startsWith("charset="))
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.map(x -> x.substring("charset=".length()))
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.findFirst()
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.orElse("ISO-8859-1"))
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.map(Charset::forName);
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}
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}
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return charset;
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}
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public static void main(String[] args) throws Exception {
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HttpClient client = HttpClient.newHttpClient();
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HttpRequest request = HttpRequest
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.newBuilder(new URI("https://hg.openjdk.org/jdk9/sandbox/jdk/shortlog/http-client-branch/"))
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.GET()
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.build();
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// This example shows how to return an InputStream that can be used to
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// start reading the response body before the response is fully received.
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// In comparison, the snipet below (which uses
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// HttpResponse.BodyHandlers.ofString()) obviously will not return before the
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// response body is fully read:
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//
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// System.out.println(
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// client.sendAsync(request, HttpResponse.BodyHandlers.ofString()).get().body());
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CompletableFuture<HttpResponse<InputStream>> handle =
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client.sendAsync(request, new HttpInputStreamHandler(3));
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if (DEBUG) err.println("Request sent");
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HttpResponse<InputStream> pending = handle.get();
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// At this point, the response headers have been received, but the
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// response body may not have arrived yet. This comes from
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// the implementation of HttpResponseInputStream::getBody above,
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// which returns an already completed completion stage, without
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// waiting for any data.
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// We can therefore access the headers - and the body, which
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// is our live InputStream, without waiting...
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HttpHeaders responseHeaders = pending.headers();
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// Get the charset declared in the response headers.
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// The optional will be empty if the content type is not
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// of type text/...
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Optional<Charset> charset = getCharset(responseHeaders);
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try (InputStream is = pending.body();
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// We assume a textual content type. Construct an InputStream
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// Reader with the appropriate Charset.
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// charset.get() will throw NPE if the content is not textual.
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Reader r = new InputStreamReader(is, charset.get())) {
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char[] buff = new char[32];
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int off=0, n=0;
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if (DEBUG) err.println("Start receiving response body");
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if (DEBUG) err.println("Charset: " + charset.get());
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// Start consuming the InputStream as the data arrives.
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// Will block until there is something to read...
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while ((n = r.read(buff, off, buff.length - off)) > 0) {
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assert (buff.length - off) > 0;
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assert n <= (buff.length - off);
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if (n == (buff.length - off)) {
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System.out.print(buff);
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off = 0;
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} else {
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off += n;
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}
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assert off < buff.length;
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}
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// last call to read may not have filled 'buff' completely.
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// flush out the remaining characters.
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assert off >= 0 && off < buff.length;
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for (int i=0; i < off; i++) {
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System.out.print(buff[i]);
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}
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// We're done!
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System.out.println("Done!");
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}
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}
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}
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