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Imagine an API returning thousands of database records. Fetching all that data at once is inefficient and can overwhelm both the server and the client.

• Slow Performance: Large payloads take longer to transfer and process.
• High Resource Usage: Both client and server use more memory and CPU.
• Poor User Experience: Users might wait a long time or see a frozen app.

This is where pagination comes in handy!

Pagination is a technique to divide a large set of results into smaller, manageable chunks called 'pages'. Instead of getting everything, you request one page at a time.

• Page Number: Which page you want (e.g., page 1, page 2).
• Page Size: How many items should be on each page (e.g., 10 items per page).

This significantly improves API performance and user experience by reducing data transfer.

Spring Data JPA provides a convenient Pageable interface to handle pagination and sorting requests. When you include Pageable as a method parameter in your controller, Spring automatically extracts the pagination (and sorting) information from the request parameters.

Common query parameters used by Spring are page (0-indexed) and size.

Let's create a simple Spring Boot REST endpoint that returns a paginated list of items. We'll use @PageableDefault to set default page and size values.

Run this application and access http://localhost:8080/api/items?page=0&size=3 in your browser.

When you call the API from the previous scene, try these URLs:

• http://localhost:8080/api/items (uses defaults: page 0, size 3)
• http://localhost:8080/api/items?page=0&size=5 (first page, 5 items)
• http://localhost:8080/api/items?page=1&size=3 (second page, 3 items)

Notice how the response includes not just the content, but also metadata like totalPages, totalElements, and number (current page number).

Just as important as limiting the data is presenting it in a meaningful order. Users often want data sorted by name, date, price, or other attributes.

For example, a list of products might be sorted alphabetically, by price (low to high), or by creation date (newest first). APIs should provide this flexibility.

The good news is that Spring Data's Pageable also handles sorting! You can specify sorting criteria directly in your API request.

• Field Name: The property to sort by (e.g., name, price).
• Direction: Whether to sort ascending (asc) or descending (desc).

The standard query parameter for sorting is sort=fieldName,direction.

Let's extend our item API to support sorting. We'll add a default sort order to @PageableDefault.

Run this application and access http://localhost:8080/api/items/sorted?page=0&size=3&sort=item,asc in your browser.

You can combine pagination and sorting in a single request! The Pageable object handles both seamlessly.

Try these URLs with the running application:

• http://localhost:8080/api/items/sorted?page=0&size=4&sort=item,desc (first page, 4 items, descending)
• http://localhost:8080/api/items/sorted?page=1&size=2&sort=item,asc (second page, 2 items, ascending)

This flexibility allows clients to retrieve exactly the data they need, how they need it.

You're building an API to list products. You want to retrieve the third page, with 10 products per page, sorted by price in descending order. Which of the following query parameters would achieve this?

We've learned how to implement pagination and sorting in Spring Boot REST APIs, making them more efficient and user-friendly.

• Pagination: Use page (0-indexed) and size to retrieve data in chunks.
• Sorting: Use sort=fieldName,direction (e.g., asc or desc) to order results.
• Spring Data's Pageable: A powerful interface that automatically handles these parameters when included in your controller methods.

These techniques are crucial for building robust APIs that can handle large datasets gracefully.