Package software.amazon.awssdk.core.internal.http

Class IdempotentAsyncResponseHandler<T,R>

java.lang.Object

software.amazon.awssdk.core.internal.http.IdempotentAsyncResponseHandler<T,R>

Type Parameters:

T - The type of the wrapped TransformingAsyncResponseHandler

R - The type of the object used to determine scope.

All Implemented Interfaces:

TransformingAsyncResponseHandler<T>, SdkAsyncHttpResponseHandler

@ThreadSafe
public class IdempotentAsyncResponseHandler<T,R>
extends Object
implements TransformingAsyncResponseHandler<T>

Wrapper for a TransformingAsyncResponseHandler that allows attachment to an external scope and given a way of evaluating whether that scope has changed or not will only allow prepare() to be called on its delegate once per state change and will cache and reserve the future that is returned by the delegate the rest of the time.

One application of this wrapper is to ensure that prepare() is not called on the underlying response handler more than once per retry no matter where or how many times its invoked.

This class is asserted to be thread-safe and it should be fine to have multiple threads call prepare() simultaneously.

Method Summary

Modifier and Type	Method	Description
static <T, R> IdempotentAsyncResponseHandler<T,R>	create(TransformingAsyncResponseHandler<T> wrappedHandler, Supplier<R> preparedScopeSupplier, BiPredicate<R,R> scopeInRangePredicate)	Creates a new wrapped TransformingAsyncResponseHandler
void	onError(Throwable error)	Called when there is an error making the request or receiving the response.
void	onHeaders(SdkHttpResponse headers)	Called when the headers have been received.
void	onStream(org.reactivestreams.Publisher<ByteBuffer> stream)	Called when the streaming body is ready.
CompletableFuture<T>	prepare()	Return the future holding the transformed response.

Methods inherited from class java.lang.Object

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

Method Details

create

public static <T,
R>
IdempotentAsyncResponseHandler<T,R> create(TransformingAsyncResponseHandler<T> wrappedHandler,
 Supplier<R> preparedScopeSupplier,
 BiPredicate<R,R> scopeInRangePredicate)

Creates a new wrapped TransformingAsyncResponseHandler

Type Parameters:

T - The type of the wrapped TransformingAsyncResponseHandler

R - The type of the object used to determine scope.

Parameters:

wrappedHandler - A different handler to wrap.

preparedScopeSupplier - A function that retrieves the current scope to determine if a new future can be prepared.

scopeInRangePredicate - A predicate that can be used to test the cached scope against the newly retrieved scope to determine if a new future can be prepared.

prepare

public CompletableFuture<T> prepare()

Description copied from interface: TransformingAsyncResponseHandler

Return the future holding the transformed response.

This method is guaranteed to be called before the request is executed, and before SdkAsyncHttpResponseHandler.onHeaders(software.amazon.awssdk.http.SdkHttpResponse) is signaled.

Specified by:

prepare in interface TransformingAsyncResponseHandler<T>

Returns:

The future holding the transformed response.

onHeaders

public void onHeaders(SdkHttpResponse headers)

Description copied from interface: SdkAsyncHttpResponseHandler

Called when the headers have been received.

Specified by:

onHeaders in interface SdkAsyncHttpResponseHandler

Parameters:

headers - The headers.

onStream

public void onStream(org.reactivestreams.Publisher<ByteBuffer> stream)

Description copied from interface: SdkAsyncHttpResponseHandler

Called when the streaming body is ready.

This method is always called. If the response does not have a body, then the publisher will complete the subscription without signalling any elements.

Specified by:

onStream in interface SdkAsyncHttpResponseHandler

Parameters:

stream - The streaming body.

onError

public void onError(Throwable error)

Description copied from interface: SdkAsyncHttpResponseHandler

Called when there is an error making the request or receiving the response. If the error is encountered while streaming the body, then the error is also delivered to the Subscriber.

Specified by:

onError in interface SdkAsyncHttpResponseHandler

Parameters:

error - The error.