software.amazon.awssdk.services.rds.paginators.DescribeDBEngineVersionsPublisher Maven / Gradle / Ivy
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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with
* the License. A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
* CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
*/
package software.amazon.awssdk.services.rds.paginators;
import java.util.Collections;
import java.util.Iterator;
import java.util.concurrent.CompletableFuture;
import java.util.function.Function;
import org.reactivestreams.Subscriber;
import software.amazon.awssdk.annotations.Generated;
import software.amazon.awssdk.core.async.SdkPublisher;
import software.amazon.awssdk.core.pagination.async.AsyncPageFetcher;
import software.amazon.awssdk.core.pagination.async.PaginatedItemsPublisher;
import software.amazon.awssdk.core.pagination.async.ResponsesSubscription;
import software.amazon.awssdk.core.util.PaginatorUtils;
import software.amazon.awssdk.services.rds.RdsAsyncClient;
import software.amazon.awssdk.services.rds.internal.UserAgentUtils;
import software.amazon.awssdk.services.rds.model.DBEngineVersion;
import software.amazon.awssdk.services.rds.model.DescribeDbEngineVersionsRequest;
import software.amazon.awssdk.services.rds.model.DescribeDbEngineVersionsResponse;
/**
*
* Represents the output for the
* {@link software.amazon.awssdk.services.rds.RdsAsyncClient#describeDBEngineVersionsPaginator(software.amazon.awssdk.services.rds.model.DescribeDbEngineVersionsRequest)}
* operation which is a paginated operation. This class is a type of {@link org.reactivestreams.Publisher} which can be
* used to provide a sequence of {@link software.amazon.awssdk.services.rds.model.DescribeDbEngineVersionsResponse}
* response pages as per demand from the subscriber.
*
*
* When the operation is called, an instance of this class is returned. At this point, no service calls are made yet and
* so there is no guarantee that the request is valid. If there are errors in your request, you will see the failures
* only after you start streaming the data. The subscribe method should be called as a request to start streaming data.
* For more info, see {@link org.reactivestreams.Publisher#subscribe(org.reactivestreams.Subscriber)}. Each call to the
* subscribe method will result in a new {@link org.reactivestreams.Subscription} i.e., a new contract to stream data
* from the starting request.
*
*
*
* The following are few ways to use the response class:
*
* 1) Using the subscribe helper method
*
*
* {@code
* software.amazon.awssdk.services.rds.paginators.DescribeDBEngineVersionsPublisher publisher = client.describeDBEngineVersionsPaginator(request);
* CompletableFuture future = publisher.subscribe(res -> { // Do something with the response });
* future.get();
* }
*
*
* 2) Using a custom subscriber
*
*
* {@code
* software.amazon.awssdk.services.rds.paginators.DescribeDBEngineVersionsPublisher publisher = client.describeDBEngineVersionsPaginator(request);
* publisher.subscribe(new Subscriber() {
*
* public void onSubscribe(org.reactivestreams.Subscriber subscription) { //... };
*
*
* public void onNext(software.amazon.awssdk.services.rds.model.DescribeDbEngineVersionsResponse response) { //... };
* });}
*
*
* As the response is a publisher, it can work well with third party reactive streams implementations like RxJava2.
*
* Please notice that the configuration of MaxRecords won't limit the number of results you get with the paginator.
* It only limits the number of results in each page.
*
*
* Note: If you prefer to have control on service calls, use the
* {@link #describeDBEngineVersions(software.amazon.awssdk.services.rds.model.DescribeDbEngineVersionsRequest)}
* operation.
*
*/
@Generated("software.amazon.awssdk:codegen")
public class DescribeDBEngineVersionsPublisher implements SdkPublisher {
private final RdsAsyncClient client;
private final DescribeDbEngineVersionsRequest firstRequest;
private final AsyncPageFetcher nextPageFetcher;
private boolean isLastPage;
public DescribeDBEngineVersionsPublisher(RdsAsyncClient client, DescribeDbEngineVersionsRequest firstRequest) {
this(client, firstRequest, false);
}
private DescribeDBEngineVersionsPublisher(RdsAsyncClient client, DescribeDbEngineVersionsRequest firstRequest,
boolean isLastPage) {
this.client = client;
this.firstRequest = UserAgentUtils.applyPaginatorUserAgent(firstRequest);
this.isLastPage = isLastPage;
this.nextPageFetcher = new DescribeDbEngineVersionsResponseFetcher();
}
@Override
public void subscribe(Subscriber subscriber) {
subscriber.onSubscribe(ResponsesSubscription.builder().subscriber(subscriber).nextPageFetcher(nextPageFetcher).build());
}
/**
* Returns a publisher that can be used to get a stream of data. You need to subscribe to the publisher to request
* the stream of data. The publisher has a helper forEach method that takes in a {@link java.util.function.Consumer}
* and then applies that consumer to each response returned by the service.
*/
public final SdkPublisher dbEngineVersions() {
Function> getIterator = response -> {
if (response != null && response.dbEngineVersions() != null) {
return response.dbEngineVersions().iterator();
}
return Collections.emptyIterator();
};
return PaginatedItemsPublisher.builder().nextPageFetcher(new DescribeDbEngineVersionsResponseFetcher())
.iteratorFunction(getIterator).isLastPage(isLastPage).build();
}
private class DescribeDbEngineVersionsResponseFetcher implements AsyncPageFetcher {
@Override
public boolean hasNextPage(final DescribeDbEngineVersionsResponse previousPage) {
return PaginatorUtils.isOutputTokenAvailable(previousPage.marker());
}
@Override
public CompletableFuture nextPage(final DescribeDbEngineVersionsResponse previousPage) {
if (previousPage == null) {
return client.describeDBEngineVersions(firstRequest);
}
return client.describeDBEngineVersions(firstRequest.toBuilder().marker(previousPage.marker()).build());
}
}
}