分页与排序
为 API 端点添加分页和排序功能，实现高效的数据检索。
分页与排序 是 CoddyKit 上的免费 Spring Boot 4 Microservices & REST APIs 课时。 这是第 2 节课，共 3 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Spring Boot 4 Microservices & REST APIs 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Spring Boot 4 Microservices & REST APIs 课程共包含 3 节课。
本课时的部分内容尚未翻译，以英文显示。
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) andsizeto retrieve data in chunks. - Sorting: Use
sort=fieldName,direction(e.g.,ascordesc) 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.
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常见问题解答
「分页与排序」课时是免费的吗？
是的 — 「分页与排序」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Spring Boot 4 Microservices & REST APIs 课程的其余内容，请升级到 CoddyKit PRO。 Spring Boot 4 Microservices & REST APIs 课程共包含 3 节课。
「分页与排序」这节课中我会学到什么？
为 API 端点添加分页和排序功能，实现高效的数据检索。 你通过在浏览器中直接运行的动手代码来练习 Spring Boot 4 Microservices & REST APIs，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Spring Boot 4 Microservices & REST APIs 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Spring Boot 4 Microservices & REST APIs 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 3 节。
「分页与排序」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Spring Boot 4 Microservices & REST APIs 课中编写并运行代码吗？
能。每节 Spring Boot 4 Microservices & REST APIs 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。