software.amazon.awssdk.services.databasemigration.paginators.DescribeEndpointsIterable Maven / Gradle / Ivy

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The AWS Java SDK for AWS Database Migration Service module holds the client classes that are used for communicating with AWS Database Migration Service.
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/*
 * Copyright 2013-2018 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.databasemigration.paginators;

import java.util.Collections;
import java.util.Iterator;
import software.amazon.awssdk.annotations.Generated;
import software.amazon.awssdk.core.pagination.sync.PaginatedResponsesIterator;
import software.amazon.awssdk.core.pagination.sync.SdkIterable;
import software.amazon.awssdk.core.pagination.sync.SyncPageFetcher;
import software.amazon.awssdk.core.util.SdkAutoConstructList;
import software.amazon.awssdk.core.util.SdkAutoConstructMap;
import software.amazon.awssdk.services.databasemigration.DatabaseMigrationClient;
import software.amazon.awssdk.services.databasemigration.model.DescribeEndpointsRequest;
import software.amazon.awssdk.services.databasemigration.model.DescribeEndpointsResponse;

/**
 * 
 * Represents the output for the
 * {@link software.amazon.awssdk.services.databasemigration.DatabaseMigrationClient#describeEndpointsPaginator(software.amazon.awssdk.services.databasemigration.model.DescribeEndpointsRequest)}
 * operation which is a paginated operation. This class is an iterable of
 * {@link software.amazon.awssdk.services.databasemigration.model.DescribeEndpointsResponse} that can be used to iterate
 * through all the response pages of the operation.
 * 
 * 
 * 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. As you iterate through the iterable, SDK will start lazily
 * loading response pages by making service calls until there are no pages left or your iteration stops. If there are
 * errors in your request, you will see the failures only after you start iterating through the iterable.
 * 
 *
 * 
 * The following are few ways to iterate through the response pages:
 * 
 * 1) Using a Stream
 * 
 *  * {@code
 * software.amazon.awssdk.services.databasemigration.paginators.DescribeEndpointsIterable responses = client.describeEndpointsPaginator(request);
 * responses.stream().forEach(....);
 * }
 * 
 *
 * 2) Using For loop
 * 
 *  * {
 *     @code
 *     software.amazon.awssdk.services.databasemigration.paginators.DescribeEndpointsIterable responses = client
 *             .describeEndpointsPaginator(request);
 *     for (software.amazon.awssdk.services.databasemigration.model.DescribeEndpointsResponse response : responses) {
 *         // do something;
 *     }
 * }
 * 
 *
 * 3) Use iterator directly
 * 
 *  * {@code
 * software.amazon.awssdk.services.databasemigration.paginators.DescribeEndpointsIterable responses = client.describeEndpointsPaginator(request);
 * responses.iterator().forEachRemaining(....);
 * }
 * 
 * 
 * Note: If you prefer to have control on service calls, use the
 * {@link #describeEndpoints(software.amazon.awssdk.services.databasemigration.model.DescribeEndpointsRequest)}
 * operation.
 * 
 */
@Generated("software.amazon.awssdk:codegen")
public class DescribeEndpointsIterable implements SdkIterable {
    private final DatabaseMigrationClient client;

    private final DescribeEndpointsRequest firstRequest;

    private final SyncPageFetcher nextPageFetcher;

    public DescribeEndpointsIterable(DatabaseMigrationClient client, DescribeEndpointsRequest firstRequest) {
        this.client = client;
        this.firstRequest = firstRequest;
        this.nextPageFetcher = new DescribeEndpointsResponseFetcher();
    }

    @Override
    public Iterator iterator() {
        return PaginatedResponsesIterator.builder().nextPageFetcher(nextPageFetcher).build();
    }

    /**
     * 
     * A helper method to resume the pages in case of unexpected failures. The method takes the last successful response
     * page as input and returns an instance of {@link DescribeEndpointsIterable} that can be used to retrieve the
     * consecutive pages that follows the input page.
     * 
     */
    private final DescribeEndpointsIterable resume(DescribeEndpointsResponse lastSuccessfulPage) {
        if (nextPageFetcher.hasNextPage(lastSuccessfulPage)) {
            return new DescribeEndpointsIterable(client, firstRequest.toBuilder().marker(lastSuccessfulPage.marker()).build());
        }
        return new DescribeEndpointsIterable(client, firstRequest) {
            @Override
            public Iterator iterator() {
                return Collections.emptyIterator();
            }
        };
    }

    private class DescribeEndpointsResponseFetcher implements SyncPageFetcher {
        @Override
        public boolean hasNextPage(DescribeEndpointsResponse previousPage) {
            return previousPage.marker() != null && !SdkAutoConstructList.class.isInstance(previousPage.marker())
                    && !SdkAutoConstructMap.class.isInstance(previousPage.marker());
        }

        @Override
        public DescribeEndpointsResponse nextPage(DescribeEndpointsResponse previousPage) {
            if (previousPage == null) {
                return client.describeEndpoints(firstRequest);
            }
            return client.describeEndpoints(firstRequest.toBuilder().marker(previousPage.marker()).build());
        }
    }
}