Spring Boot 4 Microservices & REST APIs · Aula

Paginação e ordenação

Adicione recursos de paginação e ordenação aos endpoints da sua API para recuperar dados com eficiência.

Paginação e ordenação é uma aula grátis de Spring Boot 4 Microservices & REST APIs no CoddyKit. Esta é a aula 2 de 3. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Spring Boot 4 Microservices & REST APIs, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Spring Boot 4 Microservices & REST APIs inclui 3 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Handling Large API Responses

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!

What is Pagination?

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's Pageable

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.

Implementing Pagination

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.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Pageable;
import org.springframework.data.web.PageableDefault;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
import java.util.ArrayList;

@SpringBootApplication
@RestController
public class PagingController {

    private List<String> items = List.of("Apple", "Banana", "Orange", "Grape", "Kiwi", "Mango", "Peach", "Plum", "Cherry", "Lemon", "Fig", "Date");

    @GetMapping("/api/items")
    public Page<String> getItems(
        @PageableDefault(size = 3, page = 0) Pageable pageable) {

        int start = (int) pageable.getOffset();
        int end = Math.min((start + pageable.getPageSize()), items.size());

        List<String> pagedItems = items.subList(start, end);
        return new PageImpl<>(pagedItems, pageable, items.size());
    }

    public static void main(String[] args) {
        SpringApplication.run(PagingController.class, args);
    }
}

Exploring Paged Responses

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).

Why Sorting Matters

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.

Sorting with Pageable

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.

Implementing Sorting

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.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.web.PageableDefault;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
import java.util.ArrayList;
import java.util.Comparator;

@SpringBootApplication
@RestController
public class SortingController {

    private List<String> items = new ArrayList<>(List.of("Apple", "Banana", "Orange", "Grape", "Kiwi", "Mango", "Peach", "Plum", "Cherry", "Lemon", "Fig", "Date"));

    @GetMapping("/api/items/sorted")
    public Page<String> getSortedItems(
        @PageableDefault(size = 3, page = 0, sort = "item", direction = Sort.Direction.ASC) Pageable pageable) {

        Comparator<String> comparator = Comparator.naturalOrder();
        if (pageable.getSort().isSorted() && pageable.getSort().getOrderFor("item") != null) {
            Sort.Direction direction = pageable.getSort().getOrderFor("item").getDirection();
            if (direction == Sort.Direction.DESC) {
                comparator = Comparator.reverseOrder();
            }
        }
        items.sort(comparator);

        int start = (int) pageable.getOffset();
        int end = Math.min((start + pageable.getPageSize()), items.size());

        List<String> pagedAndSortedItems = items.subList(start, end);
        return new PageImpl<>(pagedAndSortedItems, pageable, items.size());
    }

    public static void main(String[] args) {
        SpringApplication.run(SortingController.class, args);
    }
}

Combining Sort & Page

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.

Quick Check: API Parameters

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?

Recap: Pagination & Sorting

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.

Perguntas Frequentes

A aula “Paginação e ordenação” é grátis?

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O que vou aprender em “Paginação e ordenação”?

Adicione recursos de paginação e ordenação aos endpoints da sua API para recuperar dados com eficiência. Você pratica Spring Boot 4 Microservices & REST APIs com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar Spring Boot 4 Microservices & REST APIs?

Nenhuma experiência prévia é necessária. Spring Boot 4 Microservices & REST APIs no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 2 de 3.

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