Pagination and sorting with Pageable in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Pageable interface in Spring Boot?

The Pageable interface helps to request a specific page of data with a defined size and sorting order. It makes it easy to handle pagination and sorting in database queries.

beginner

How do you specify sorting when using Pageable?

You can specify sorting by using PageRequest.of(page, size, Sort.by("fieldName").ascending()) or PageRequest.of(page, size, Sort.by("fieldName").descending()) to sort the results by a field in ascending or descending order.

intermediate

What does the Page object returned by a repository method contain?

The Page object contains the list of items for the requested page, total number of pages, total number of elements, current page number, and page size. It helps to navigate through paged data easily.

beginner

How can you enable pagination and sorting in a Spring Data JPA repository method?

Add a Pageable parameter to the repository method signature, for example: Page<Entity> findAll(Pageable pageable);. Spring Data will automatically apply pagination and sorting based on the Pageable argument.

advanced

What is the difference between Pageable and Slice in Spring Data?

Pageable returns a Page which contains total count information, while Slice only knows if there is a next slice available and does not fetch total count, which can improve performance when total count is not needed.

Which method creates a Pageable object for page 2 with 10 items per page sorted by 'name' ascending?

A PageRequest.of(0, 10, Sort.by("name").ascending())

B PageRequest.of(2, 10, Sort.by("name").ascending())

C PageRequest.of(1, 10, Sort.by("name").ascending())

D PageRequest.of(1, 10, Sort.by("name").descending())

Page numbers are zero-based, so page 2 means index 1. The correct call is PageRequest.of(1, 10, Sort.by("name").ascending()).

What does the Page interface provide besides the list of items?

A Only the list of items

B Sorting configuration only

C Database connection info

D Total pages, total elements, current page number, page size

Page provides metadata like total pages, total elements, current page number, and page size along with the content.

How do you add pagination support to a Spring Data JPA repository method?

A Add a <code>Pageable</code> parameter to the method

B Add a <code>Sort</code> parameter only

C Use <code>List</code> return type

D No changes needed

Adding a Pageable parameter enables pagination and sorting automatically.

Which of the following is true about Slice compared to Page?

A <code>Slice</code> does not contain total count information

B <code>Slice</code> contains total pages info

C <code>Slice</code> fetches all data at once

D <code>Slice</code> is deprecated

Slice only knows if there is a next slice and does not fetch total count, improving performance.

What is the default sort direction if not specified in Pageable?

A Ascending

B No sorting applied

C Random

D Descending

If no Sort is provided when creating the Pageable, no sorting is applied.

Explain how to implement pagination and sorting in a Spring Boot REST API using Pageable.

Think about how to request a specific page and sort order, and how to return the data with helpful info.

Describe the difference between Page and Slice in Spring Data pagination.

Focus on what metadata each provides and when you might prefer one over the other.

Practice

1. What is the main purpose of using Pageable in Spring Boot?

easy

A. To fetch data in small chunks with optional sorting

B. To connect to the database directly

C. To write SQL queries manually

D. To handle user authentication

Solution

1. Step 1: Understand Pageable's role

   Pageable is used to request data in pages, not all at once.

2. Step 2: Recognize sorting feature

   It also supports sorting data by fields while fetching pages.

3. Final Answer:

   To fetch data in small chunks with optional sorting -> Option A

4. Quick Check:

   Pageable = Pagination + Sorting [OK]

Hint: Pageable means small pages + sorting [OK]

Common Mistakes:

• Thinking Pageable connects to database
• Confusing Pageable with authentication
• Assuming Pageable writes SQL queries

2. Which of the following is the correct way to create a Pageable object for page 2, size 5, sorted by "name" ascending?

easy

A. PageRequest.of(1, 5, Sort.by("name"))

B. PageRequest.of(2, 5, Sort.asc("name"))

C. PageRequest.of(2, 5, Sort.by("name"))

D. PageRequest.create(2, 5, Sort.by("name"))

Solution

1. Step 1: Understand zero-based page index

   Page numbers start at 0, so page 2 means index 1.

2. Step 2: Check method and sorting syntax

   Use PageRequest.of(page, size, Sort.by("field")) for ascending sort.

3. Final Answer:

   PageRequest.of(1, 5, Sort.by("name")) -> Option A

4. Quick Check:

   Page index zero-based + Sort.by correct [OK]

Hint: Page index starts at 0, so page 2 is index 1 [OK]

Common Mistakes:

• Using page number directly instead of zero-based index
• Using non-existent methods like Sort.asc
• Using PageRequest.create instead of PageRequest.of

3. Given this repository method call:
repository.findAll(PageRequest.of(0, 3, Sort.by("age")))
What will be the result?

medium

A. Error because Sort direction is missing

B. First 3 records sorted by age descending

C. All records without sorting

D. First 3 records sorted by age ascending

Solution

1. Step 1: Analyze PageRequest parameters

   Page 0 means first page, size 3 means 3 records, Sort.by("age") defaults to ascending.

2. Step 2: Understand repository behavior

   findAll with Pageable returns that page of sorted data.

3. Final Answer:

   First 3 records sorted by age ascending -> Option D

4. Quick Check:

   Page 0 + size 3 + ascending sort = first 3 sorted [OK]

Hint: Sort.by defaults to ascending if direction not set [OK]

Common Mistakes:

• Assuming descending sort without direction
• Thinking all records are returned
• Expecting error due to missing direction

4. What is wrong with this code snippet?

Pageable pageable = PageRequest.of(1, 10, Sort.asc("date"));

medium

A. Page index should start at 0, not 1

B. Sort.asc() method does not exist

C. Page size cannot be 10

D. PageRequest.of requires 4 parameters

Solution

1. Step 1: Check Sort method usage

   Spring Data uses Sort.by(), not Sort.asc().

2. Step 2: Verify other parameters

   Page index 1 and size 10 are valid; PageRequest.of takes 3 parameters here.

3. Final Answer:

   Sort.asc() method does not exist -> Option B

4. Quick Check:

   Use Sort.by() for sorting [OK]

Hint: Use Sort.by(), not Sort.asc() [OK]

Common Mistakes:

• Using Sort.asc() or Sort.desc() which don't exist
• Thinking page index must be 0 always
• Believing PageRequest.of needs 4 parameters

5. You want to fetch the third page of size 4, sorted by "price" descending and then by "name" ascending. Which Pageable creation is correct?

hard

A. PageRequest.of(2, 4, Sort.by("price", "name"))

B. PageRequest.of(3, 4, Sort.by("price").descending().and(Sort.by("name")))

C. PageRequest.of(2, 4, Sort.by(Sort.Order.desc("price"), Sort.Order.asc("name")))

D. PageRequest.of(2, 4, Sort.by("price").desc().and(Sort.by("name").asc()))

Solution

1. Step 1: Identify zero-based page index

   Third page means index 2 (0,1,2).

2. Step 2: Create Sort with multiple orders

   Use Sort.by(Order.desc("price"), Order.asc("name")) to combine sorting directions.

3. Step 3: Check syntax correctness

   PageRequest.of(2, 4, Sort.by(Sort.Order.desc("price"), Sort.Order.asc("name"))) uses correct PageRequest.of and Sort.by with orders.

4. Final Answer:

   PageRequest.of(2, 4, Sort.by(Sort.Order.desc("price"), Sort.Order.asc("name"))) -> Option C

5. Quick Check:

   Page 2 + size 4 + multi-sort orders correct [OK]

Hint: Use Sort.Order for multi-direction sorting [OK]

Common Mistakes:

• Using page number 3 instead of index 2
• Trying to chain .desc() or .asc() methods that don't exist
• Passing multiple fields without specifying order