Module java.net.http

Package java.net.http

Class HttpResponse.BodySubscribers

java.lang.Object

java.net.http.HttpResponse.BodySubscribers

Enclosing interface:

HttpResponse<T>

public static class HttpResponse.BodySubscribers
extends Object

Implementations of BodySubscriber that implement various useful subscribers, such as converting the response body bytes into a String, or streaming the bytes to a file.

The following are examples of using the predefined body subscribers to convert a flow of response body data into common high-level Java objects:

// Streams the response body to a File
HttpResponse<Path> response = client
  .send(request, responseInfo -> BodySubscribers.ofFile(Paths.get("example.html"));

// Accumulates the response body and returns it as a byte[]
HttpResponse<byte[]> response = client
  .send(request, responseInfo -> BodySubscribers.ofByteArray());

// Discards the response body
HttpResponse<Void> response = client
  .send(request, responseInfo -> BodySubscribers.discarding());

// Accumulates the response body as a String then maps it to its bytes
HttpResponse<byte[]> response = client
  .send(request, responseInfo ->
     BodySubscribers.mapping(BodySubscribers.ofString(UTF_8), String::getBytes));

Since:

11

Method Summary

Modifier and Type	Method	Description
static <T> HttpResponse.BodySubscriber<T>	buffering(HttpResponse.BodySubscriber<T> downstream, int bufferSize)	Returns a BodySubscriber which buffers data before delivering it to the given downstream subscriber.
static HttpResponse.BodySubscriber<Void>	discarding()	Returns a response subscriber which discards the response body.
static HttpResponse.BodySubscriber<Void>	fromLineSubscriber(Flow.Subscriber<? super String> subscriber)	Returns a body subscriber that forwards all response body to the given Flow.Subscriber, line by line.
static <S extends Flow.Subscriber<? super String>, T> HttpResponse.BodySubscriber<T>	fromLineSubscriber(S subscriber, Function<? super S,? extends T> finisher, Charset charset, String lineSeparator)	Returns a body subscriber that forwards all response body to the given Flow.Subscriber, line by line.
static HttpResponse.BodySubscriber<Void>	fromSubscriber(Flow.Subscriber<? super List<ByteBuffer>> subscriber)	Returns a body subscriber that forwards all response body to the given Flow.Subscriber.
static <S extends Flow.Subscriber<? super List<ByteBuffer>>, T> HttpResponse.BodySubscriber<T>	fromSubscriber(S subscriber, Function<? super S,? extends T> finisher)	Returns a body subscriber that forwards all response body to the given Flow.Subscriber.
static <T, U> HttpResponse.BodySubscriber<U>	mapping(HttpResponse.BodySubscriber<T> upstream, Function<? super T,? extends U> mapper)	Returns a BodySubscriber whose response body value is that of the result of applying the given function to the body object of the given upstream BodySubscriber.
static HttpResponse.BodySubscriber<byte[]>	ofByteArray()	Returns a BodySubscriber which stores the response body as a byte array.
static HttpResponse.BodySubscriber<Void>	ofByteArrayConsumer(Consumer<Optional<byte[]>> consumer)	Returns a BodySubscriber which provides the incoming body data to the provided Consumer of Optional<byte[]>.
static HttpResponse.BodySubscriber<Path>	ofFile(Path file)	Returns a BodySubscriber which stores the response body in a file opened with the given name.
static HttpResponse.BodySubscriber<Path>	ofFile(Path file, OpenOption... openOptions)	Returns a BodySubscriber which stores the response body in a file opened with the given options and name.
static HttpResponse.BodySubscriber<InputStream>	ofInputStream()	Returns a BodySubscriber which streams the response body as an InputStream.
static HttpResponse.BodySubscriber<Stream<String>>	ofLines(Charset charset)	Returns a BodySubscriber which streams the response body as a Stream<String>, where each string in the stream corresponds to a line as defined by BufferedReader.lines().
static HttpResponse.BodySubscriber<Flow.Publisher<List<ByteBuffer>>>	ofPublisher()	Returns a response subscriber which publishes the response body through a Publisher<List<ByteBuffer>>.
static HttpResponse.BodySubscriber<String>	ofString(Charset charset)	Returns a body subscriber which stores the response body as a String converted using the given Charset.
static <U> HttpResponse.BodySubscriber<U>	replacing(U value)	Returns a response subscriber which discards the response body.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

fromSubscriber

public static HttpResponse.BodySubscriber<Void> fromSubscriber(Flow.Subscriber<? super List<ByteBuffer>> subscriber)

Returns a body subscriber that forwards all response body to the given Flow.Subscriber. The completion stage of the returned body subscriber completes after one of the given subscribers onComplete or onError has been invoked.

API Note:

This method can be used as an adapter between BodySubscriber and Flow.Subscriber.

Parameters:

subscriber - the subscriber

Returns:

a body subscriber

fromSubscriber

public static <S extends Flow.Subscriber<? super List<ByteBuffer>>,
T>
HttpResponse.BodySubscriber<T> fromSubscriber(S subscriber,
 Function<? super S,? extends T> finisher)

Returns a body subscriber that forwards all response body to the given Flow.Subscriber. The completion stage of the returned body subscriber completes after one of the given subscribers onComplete or onError has been invoked.

The given finisher function is applied after the given subscriber's onComplete has been invoked. The finisher function is invoked with the given subscriber, and returns a value that is set as the response's body.

API Note:

This method can be used as an adapter between BodySubscriber and Flow.Subscriber.

Type Parameters:

S - the type of the Subscriber

T - the type of the response body

Parameters:

subscriber - the subscriber

finisher - a function to be applied after the subscriber has completed

Returns:

a body subscriber

fromLineSubscriber

public static HttpResponse.BodySubscriber<Void> fromLineSubscriber(Flow.Subscriber<? super String> subscriber)

Returns a body subscriber that forwards all response body to the given Flow.Subscriber, line by line. The completion stage of the returned body subscriber completes after one of the given subscribers onComplete or onError has been invoked. Bytes are decoded using the UTF-8 charset, and lines are delimited in the manner of BufferedReader.readLine().

API Note:

This method can be used as an adapter between BodySubscriber and Flow.Subscriber.

Implementation Note:

This is equivalent to calling

fromLineSubscriber(subscriber, s -> null, StandardCharsets.UTF_8, null)

Parameters:

subscriber - the subscriber

Returns:

a body subscriber

fromLineSubscriber

public static <S extends Flow.Subscriber<? super String>,
T>
HttpResponse.BodySubscriber<T> fromLineSubscriber(S subscriber,
 Function<? super S,? extends T> finisher,
 Charset charset,
 String lineSeparator)

Returns a body subscriber that forwards all response body to the given Flow.Subscriber, line by line. The completion stage of the returned body subscriber completes after one of the given subscribers onComplete or onError has been invoked.

The given finisher function is applied after the given subscriber's onComplete has been invoked. The finisher function is invoked with the given subscriber, and returns a value that is set as the response's body.

API Note:

This method can be used as an adapter between BodySubscriber and Flow.Subscriber.

Type Parameters:

S - the type of the Subscriber

T - the type of the response body

Parameters:

subscriber - the subscriber

finisher - a function to be applied after the subscriber has completed

charset - a Charset to decode the bytes

lineSeparator - an optional line separator: can be null, in which case lines will be delimited in the manner of BufferedReader.readLine().

Returns:

a body subscriber

Throws:

IllegalArgumentException - if the supplied lineSeparator is the empty string

ofString

public static HttpResponse.BodySubscriber<String> ofString(Charset charset)

Returns a body subscriber which stores the response body as a String converted using the given Charset.

The HttpResponse using this subscriber is available after the entire response has been read.

Parameters:

charset - the character set to convert the String with

Returns:

a body subscriber

ofByteArray

public static HttpResponse.BodySubscriber<byte[]> ofByteArray()

Returns a BodySubscriber which stores the response body as a byte array.

The HttpResponse using this subscriber is available after the entire response has been read.

Returns:

a body subscriber

ofFile

public static HttpResponse.BodySubscriber<Path> ofFile(Path file,
 OpenOption... openOptions)

Returns a BodySubscriber which stores the response body in a file opened with the given options and name. The file will be opened with the given options using FileChannel.open just before the body is read. Any exception thrown will be returned or thrown from HttpClient::send or HttpClient::sendAsync as appropriate.

The HttpResponse using this subscriber is available after the entire response has been read.

In the case of the default file system provider, security manager permission checks are performed in this factory method, when the BodySubscriber is created. Otherwise, permission checks may be performed asynchronously against the caller's context at file access time. Care must be taken that the BodySubscriber is not shared with untrusted code.

Parameters:

file - the file to store the body in

openOptions - the list of options to open the file with

Returns:

a body subscriber

Throws:

IllegalArgumentException - if an invalid set of open options are specified

SecurityException - in the case of the default file system provider, and a security manager is installed, checkWrite is invoked to check write access to the given file

ofFile

public static HttpResponse.BodySubscriber<Path> ofFile(Path file)

Returns a BodySubscriber which stores the response body in a file opened with the given name.

Equivalent to: ofFile(file, CREATE, WRITE)

In the case of the default file system provider, security manager permission checks are performed in this factory method, when the BodySubscriber is created. Otherwise, permission checks may be performed asynchronously against the caller's context at file access time. Care must be taken that the BodySubscriber is not shared with untrusted code.

Parameters:

file - the file to store the body in

Returns:

a body subscriber

Throws:

SecurityException - in the case of the default file system provider, and a security manager is installed, checkWrite is invoked to check write access to the given file

ofByteArrayConsumer

public static HttpResponse.BodySubscriber<Void> ofByteArrayConsumer(Consumer<Optional<byte[]>> consumer)

Returns a BodySubscriber which provides the incoming body data to the provided Consumer of Optional<byte[]>. Each call to Consumer.accept() will contain a non empty Optional, except for the final invocation after all body data has been read, when the Optional will be empty.

The HttpResponse using this subscriber is available after the entire response has been read.

API Note:

This subscriber is not flow controlled. Therefore, the supplied consumer must be able to process whatever amount of data is delivered in a timely fashion.

Parameters:

consumer - a Consumer of byte arrays

Returns:

a BodySubscriber

ofInputStream

public static HttpResponse.BodySubscriber<InputStream> ofInputStream()

Returns a BodySubscriber which streams the response body as an InputStream.

The HttpResponse using this subscriber is available immediately after the response headers have been read, without requiring to wait for the entire body to be processed. The response body can then be read directly from the InputStream.

API Note:

To ensure that all resources associated with the corresponding exchange are properly released the caller must ensure to either read all bytes until EOF is reached, or call InputStream.close() if it is unable or unwilling to do so. Calling close before exhausting the stream may cause the underlying HTTP connection to be closed and prevent it from being reused for subsequent operations.

Implementation Note:

The read method of the InputStream returned by the default implementation of this method will throw an IOException with the thread interrupt status set if the thread is interrupted while blocking on read. In that case, the request will also be cancelled and the InputStream will be closed.

Returns:

a body subscriber that streams the response body as an InputStream.

ofLines

public static HttpResponse.BodySubscriber<Stream<String>> ofLines(Charset charset)

Returns a BodySubscriber which streams the response body as a Stream<String>, where each string in the stream corresponds to a line as defined by BufferedReader.lines().

The HttpResponse using this subscriber is available immediately after the response headers have been read, without requiring to wait for the entire body to be processed. The response body can then be read directly from the Stream.

API Note:

To ensure that all resources associated with the corresponding exchange are properly released the caller must ensure to either read all lines until the stream is exhausted, or call BaseStream.close() if it is unable or unwilling to do so. Calling close before exhausting the stream may cause the underlying HTTP connection to be closed and prevent it from being reused for subsequent operations.

Parameters:

charset - the character set to use when converting bytes to characters

Returns:

a body subscriber that streams the response body as a Stream<String>.

See Also:

• BufferedReader.lines()

ofPublisher

public static HttpResponse.BodySubscriber<Flow.Publisher<List<ByteBuffer>>> ofPublisher()

Returns a response subscriber which publishes the response body through a Publisher<List<ByteBuffer>>.

The HttpResponse using this subscriber is available immediately after the response headers have been read, without requiring to wait for the entire body to be processed. The response body bytes can then be obtained by subscribing to the publisher returned by the HttpResponse body method.

The publisher returned by the body method can be subscribed to only once. The first subscriber will receive the body response bytes if successfully subscribed, or will cause the subscription to be cancelled otherwise. If more subscriptions are attempted, the subsequent subscribers will be immediately subscribed with an empty subscription and their onError method will be invoked with an IllegalStateException.

API Note:

To ensure that all resources associated with the corresponding exchange are properly released the caller must ensure that the provided publisher is subscribed once, and either requests all bytes until onComplete or onError are invoked, or cancel the provided subscription if it is unable or unwilling to do so. Note that depending on the actual HTTP protocol version used for the exchange, cancelling the subscription instead of exhausting the flow may cause the underlying HTTP connection to be closed and prevent it from being reused for subsequent operations.

Returns:

A BodySubscriber which publishes the response body through a Publisher<List<ByteBuffer>>.

replacing

public static <U> HttpResponse.BodySubscriber<U> replacing(U value)

Returns a response subscriber which discards the response body. The supplied value is the value that will be returned from HttpResponse.body().

Type Parameters:

U - the type of the response body

Parameters:

value - the value to return from HttpResponse.body(), may be null

Returns:

a BodySubscriber

discarding

public static HttpResponse.BodySubscriber<Void> discarding()

Returns a response subscriber which discards the response body.

Returns:

a response body subscriber

buffering

public static <T> HttpResponse.BodySubscriber<T> buffering(HttpResponse.BodySubscriber<T> downstream,
 int bufferSize)

Returns a BodySubscriber which buffers data before delivering it to the given downstream subscriber. The subscriber guarantees to deliver bufferSize bytes of data to each invocation of the downstream's onNext method, except for the final invocation, just before onComplete is invoked. The final invocation of onNext may contain fewer than bufferSize bytes.

The returned subscriber delegates its getBody() method to the downstream subscriber.

Type Parameters:

T - the type of the response body

Parameters:

downstream - the downstream subscriber

bufferSize - the buffer size

Returns:

a buffering body subscriber

Throws:

IllegalArgumentException - if bufferSize <= 0

mapping

public static <T,
U> HttpResponse.BodySubscriber<U> mapping(HttpResponse.BodySubscriber<T> upstream,
 Function<? super T,? extends U> mapper)

Returns a BodySubscriber whose response body value is that of the result of applying the given function to the body object of the given upstream BodySubscriber.

The mapping function is executed using the client's executor, and can therefore be used to map any response body type, including blocking InputStream. However, performing any blocking operation in the mapper function runs the risk of blocking the executor's thread for an unknown amount of time (at least until the blocking operation finishes), which may end up starving the executor of available threads. Therefore, in the case where mapping to the desired type might block (e.g. by reading on the InputStream), then mapping to a Supplier of the desired type and deferring the blocking operation until Supplier::get is invoked by the caller's thread should be preferred, as shown in the following example which uses a well-known JSON parser to convert an InputStream into any annotated Java type.

For example:

 public static <W> BodySubscriber<Supplier<W>> asJSON(Class<W> targetType) {
   BodySubscriber<InputStream> upstream = BodySubscribers.ofInputStream();

   BodySubscriber<Supplier<W>> downstream = BodySubscribers.mapping(
         upstream,
         (InputStream is) -> () -> {
             try (InputStream stream = is) {
                 ObjectMapper objectMapper = new ObjectMapper();
                 return objectMapper.readValue(stream, targetType);
             } catch (IOException e) {
                 throw new UncheckedIOException(e);
             }
         });
  return downstream;
}

Type Parameters:

T - the upstream body type

U - the type of the body subscriber returned

Parameters:

upstream - the body subscriber to be mapped

mapper - the mapping function

Returns:

a mapping body subscriber