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