How do you use the Page interface to return paginated results?

Table of Contents

• Introduction
  • What is the Page Interface?
  • Returning Paginated Results Using the Page Interface
    • 1. Define the Repository with Pagination Support
    • 2. Use the Pageable Interface to Request Paginated Data
    • 3. Handling the Page Object
  • Example of Paginated API Response
  • Practical Example: Combining Pagination with Sorting
• Conclusion

Introduction

In Spring Data JPA, the Page interface is used to represent a single page of data returned from a paginated query. It encapsulates both the content (data for the current page) and the metadata (such as total number of elements, total number of pages, current page number, etc.). By using the Page interface along with the Pageable interface, you can easily implement pagination and efficiently handle large datasets.

This guide will explain how to use the Page interface to return paginated results in Spring Data JPA with practical examples.

What is the Page Interface?

The Page interface is part of Spring Data JPA and is typically returned by repository methods when performing pagination. It extends the Slice interface and provides additional methods to handle pagination metadata like total pages, total elements, and current page number.

Key features of the Page interface include:

• Content: The data on the current page (typically a list of entities).
• Total Elements: The total number of elements available in the dataset.
• Total Pages: The total number of pages available based on the current page size.
• Number of Elements: The number of elements in the current page.
• Page Number: The current page number (0-based index).

Returning Paginated Results Using the Page Interface

1. Define the Repository with Pagination Support

To use the Page interface, ensure that your repository extends either JpaRepository or PagingAndSortingRepository. Both of these interfaces provide built-in support for pagination through the findAll(Pageable pageable) method, which returns a Page object.

Example:

Here, Product is the entity, and Long is the ID type.

2. Use the Pageable Interface to Request Paginated Data

To request paginated data, you need to create a Pageable object, typically using PageRequest.of(page, size), where page is the page index (0-based) and size is the number of items per page.

You can then pass the Pageable object to the repository method, which will return a Page object.

Example:

In this example:

• PageRequest.of(page, size) creates a Pageable object.
• productRepository.findAll(pageable) fetches the paginated data from the database.
• The Page<Product> returned contains both the data (the products for the requested page) and pagination metadata (e.g., total pages, current page, etc.).

3. Handling the Page Object

The Page interface contains both the content (current page's data) and metadata. Here are some useful methods you can use when working with a Page object:

• getContent(): Returns a list of entities (the actual data for the page).
• getTotalPages(): Returns the total number of pages.
• getTotalElements(): Returns the total number of elements across all pages.
• getNumber(): Returns the current page number (zero-based index).
• getSize(): Returns the number of elements per page.
• getNumberOfElements(): Returns the number of elements on the current page.

Example:

Example of Paginated API Response

When a client sends a request like /products?page=1&size=5, the Page object returned can be used to construct a paginated response.

Response Example:

In the response:

• content: Contains the actual data (the products for the current page).
• totalElements: The total number of products available.
• totalPages: The total number of pages based on the page size.
• size: The number of products per page.
• number: The current page number (starting from 0).

Practical Example: Combining Pagination with Sorting

You can also combine pagination with sorting by using the Sort object. For example, if you want to retrieve the first page of products sorted by price in descending order:

In this example, products are paginated and sorted by the sortBy parameter (e.g., price), in descending order.

Conclusion

The Page interface in Spring Data JPA is essential for implementing pagination and retrieving large datasets in smaller, manageable chunks. It allows you to easily access both the data and the pagination metadata, helping to create efficient and user-friendly applications. By combining Pageable and Page objects, you can efficiently handle pagination and sorting without writing custom pagination logic. This makes working with large datasets simple, scalable, and efficient in Spring Data JPA.