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Add scrolling sample for JPA.
Closes #662
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‎jpa/example/src/main/java/example/springdata/jpa/pagination/Author.java

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/*
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* Copyright 2023 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package example.springdata.jpa.pagination;
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import jakarta.persistence.Entity;
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import jakarta.persistence.Id;
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import jakarta.persistence.Table;
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import lombok.Data;
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/**
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* @author Christoph Strobl
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*/
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@Data
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@Entity
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@Table(name = "authors")
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public class Author {
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@Id
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private String id;
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private String firstName;
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private String lastName;
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}

‎jpa/example/src/main/java/example/springdata/jpa/pagination/Book.java

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/*
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* Copyright 2023 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package example.springdata.jpa.pagination;
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import java.util.Date;
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import jakarta.persistence.Entity;
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import jakarta.persistence.Id;
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import jakarta.persistence.ManyToOne;
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import jakarta.persistence.Table;
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import lombok.Data;
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/**
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* @author Christoph Strobl
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*/
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@Data
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@Entity
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@Table(name = "books")
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public class Book {
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@Id
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private String id;
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private String title;
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private String isbn10;
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private Date publicationDate;
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@ManyToOne
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Author author;
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}

‎jpa/example/src/main/java/example/springdata/jpa/pagination/BookRepository.java

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/*
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* Copyright 2023 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package example.springdata.jpa.pagination;
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import org.springframework.data.domain.Page;
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import org.springframework.data.domain.Pageable;
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import org.springframework.data.domain.ScrollPosition;
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import org.springframework.data.domain.Slice;
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import org.springframework.data.domain.Window;
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import org.springframework.data.repository.ListCrudRepository;
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/**
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* @author Christoph Strobl
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*/
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public interface BookRepository extends ListCrudRepository<Book, String> {
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/**
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* Uses an {@literal offset} based pagination that first sorts the entries by their {@link Book#getPublicationDate() publication_date}
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* and then limits the result by dropping the number of rows specified in the {@link Pageable#getOffset() offset} clause.
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* To retrieve {@link Page#getTotalElements()} an additional count query is executed.
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*
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* @param title
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* @param pageable
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* @return
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*/
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Page<Book> findByTitleContainsOrderByPublicationDate(String title, Pageable pageable);
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/**
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* Uses an {@literal offset} based slicing that first sorts the entries by their {@link Book#getPublicationDate() publication_date}
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* and then limits the result by dropping the number of rows specified in the {@link Pageable#getOffset() offset} clause.
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*
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* @param title
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* @param pageable
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* @return
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*/
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Slice<Book> findBooksByTitleContainsOrderByPublicationDate(String title, Pageable pageable);
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/**
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* Depending on the provided {@link ScrollPosition} either {@link org.springframework.data.domain.OffsetScrollPosition offset}
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* or {@link org.springframework.data.domain.KeysetScrollPosition keyset} scrolling is possible.
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* Scrolling through results requires a stable {@link org.springframework.data.domain.Sort} which is different from
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* what {@link Pageable#getSort()} offers.
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* The {@literal limit} is defined via the {@literal Top} keyword.
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*
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* @param title
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* @param scrollPosition
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* @return
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*/
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Window<Book> findTop2ByTitleContainsOrderByPublicationDate(String title, ScrollPosition scrollPosition);
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}

‎jpa/example/src/main/java/example/springdata/jpa/pagination/PagingRepoConfig.java

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/*
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* Copyright 2023 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package example.springdata.jpa.pagination;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
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/**
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* @author Christoph Strobl
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*/
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@SpringBootApplication
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@EnableJpaRepositories(repositoryBaseClass = BookRepository.class)
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class PagingRepoConfig {
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}

‎jpa/example/src/test/java/example/springdata/jpa/pagination/PaginationTests.java

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/*
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* Copyright 2023 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package example.springdata.jpa.pagination;
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import static org.assertj.core.api.AssertionsForClassTypes.*;
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import java.util.List;
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import java.util.Random;
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import java.util.UUID;
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import java.util.concurrent.TimeUnit;
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import java.util.stream.Collectors;
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import java.util.stream.IntStream;
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import com.github.javafaker.Faker;
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import jakarta.persistence.EntityManager;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
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import org.springframework.boot.test.context.SpringBootTest;
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import org.springframework.context.annotation.Configuration;
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import org.springframework.data.domain.KeysetScrollPosition;
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import org.springframework.data.domain.OffsetScrollPosition;
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import org.springframework.data.domain.Page;
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import org.springframework.data.domain.PageRequest;
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import org.springframework.data.domain.Pageable;
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import org.springframework.data.domain.ScrollPosition;
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import org.springframework.data.domain.Slice;
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import org.springframework.data.domain.Window;
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import org.springframework.transaction.annotation.Transactional;
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/**
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* Show different types of paging styles using {@link Page}, {@link org.springframework.data.domain.Slice} and {@link Window}
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*
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* @author Christoph Strobl
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*/
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@SpringBootTest
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@Transactional
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class PaginationTests {
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@Configuration
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@EnableAutoConfiguration
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static class Config {
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}
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@Autowired
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BookRepository books;
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@BeforeEach
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void setUp() {
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Faker faker = new Faker();
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// create some sample data
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List<Author> authorList = createAuthors(faker);
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createBooks(faker, authorList);
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}
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/**
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* Page through the results using an offset/limit approach where the server skips over the number of results
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* specified via {@link Pageable#getOffset()}.
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* The {@link Page} return type will run an additional {@literal count} query to read the total number of matching rows
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* on each request.
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*/
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@Test
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void pageThroughResultsWithSkipAndLimit() {
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Page<Book> page;
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Pageable pageRequest = PageRequest.of(0, 2);
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do {
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page = books.findByTitleContainsOrderByPublicationDate("the", pageRequest);
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assertThat(page.getContent().size()).isGreaterThanOrEqualTo(1).isLessThanOrEqualTo(2);
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pageRequest = page.nextPageable();
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} while (page.hasNext());
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}
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/**
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* Run through the results using an offset/limit approach where the server skips over the number of results specified
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* via {@link Pageable#getOffset()}.
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* No additional {@literal count} query to read the total number of matching rows is issued. Still {@link Slice} requests,
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* but does not emit, one row more than specified via {@link Page#getSize()} to feed {@link Slice#hasNext()}
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*/
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@Test
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void sliceThroughResultsWithSkipAndLimit() {
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Slice<Book> slice;
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Pageable pageRequest = PageRequest.of(0, 2);
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do {
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slice = books.findBooksByTitleContainsOrderByPublicationDate("the", pageRequest);
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assertThat(slice.getContent().size()).isGreaterThanOrEqualTo(1).isLessThanOrEqualTo(2);
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pageRequest = slice.nextPageable();
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} while (slice.hasNext());
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}
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/**
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* Scroll through the results using an offset/limit approach where the server skips over the number of results
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* specified via {@link OffsetScrollPosition#getOffset()}.
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* <p>
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* This approach is similar to the {@link #sliceThroughResultsWithSkipAndLimit() slicing one}.
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*/
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@Test
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void scrollThroughResultsWithSkipAndLimit() {
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Window<Book> window;
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ScrollPosition scrollPosition = OffsetScrollPosition.initial();
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do {
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window = books.findTop2ByTitleContainsOrderByPublicationDate("the", scrollPosition);
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assertThat(window.getContent().size()).isGreaterThanOrEqualTo(1).isLessThanOrEqualTo(2);
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scrollPosition = window.positionAt(window.getContent().size() - 1);
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} while (window.hasNext());
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}
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/**
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* Scroll through the results using an index based approach where the {@link KeysetScrollPosition#getKeys() keyset}
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* keeps track of already seen values to resume scrolling by altering the where clause to only return rows after the
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* values contained in the keyset.
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* Set {@literal logging.level.org.hibernate.SQL=debug} to show the modified query in the log.
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*/
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@Test
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void scrollThroughResultsWithKeyset() {
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Window<Book> window;
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ScrollPosition scrollPosition = KeysetScrollPosition.initial();
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do {
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window = books.findTop2ByTitleContainsOrderByPublicationDate("the", scrollPosition);
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assertThat(window.getContent().size()).isGreaterThanOrEqualTo(1).isLessThanOrEqualTo(2);
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scrollPosition = window.positionAt(window.getContent().size() - 1);
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} while (window.hasNext());
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}
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// --> Test Data
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@Autowired
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EntityManager em;
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private List<Author> createAuthors(Faker faker) {
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List<Author> authors = IntStream.range(0, 10).mapToObj(id -> {
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Author author = new Author();
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author.setId("author-%s".formatted(id));
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author.setFirstName(faker.name().firstName());
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author.setLastName(faker.name().lastName());
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em.persist(author);
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return author;
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}).collect(Collectors.toList());
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return authors;
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}
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private List<Book> createBooks(Faker faker, List<Author> authors) {
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Random rand = new Random();
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return IntStream.range(0, 100)
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.mapToObj(id -> {
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Book book = new Book();
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book.setId("book-%03d".formatted(id));
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book.setTitle(faker.book().title());
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book.setIsbn10(UUID.randomUUID().toString().substring(0, 10));
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book.setPublicationDate(faker.date().past(5000, TimeUnit.DAYS));
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book.setAuthor(authors.get(rand.nextInt(authors.size())));
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em.persist(book);
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return book;
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}).collect(Collectors.toList());
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}
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}

‎pom.xml

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<artifactId>junit-vintage-engine</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>com.github.javafaker</groupId>
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<artifactId>javafaker</artifactId>
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<version>1.0.1</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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