SpringQuickPoll

Part 6 - Pagination

• To optimize performance, it is important to limit the amount of data returned, especially in the case of a mobile client.
• REST services have the ability to give clients access large datasets in manageable chunks, by splitting the data into discrete pages or paging data.
• For this lab, we will approach this by implementing the page number pagination pattern.

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Get Data From Page

• For example, a client wanting a blog post in page 3 of a hypothetical blog service can use a GET method resembling the following: http://blog.example.com/posts?page=3

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Limit Data Retrieved From Page

• It is possible for the client to override the default page size by passing in a page-size parameter: http://blog.example.com/posts?page=3&size=20

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Pagination Data

• Pagination-specific information includes
  • total number of records
  • total number of pages
  • current page number
  • page size
• In the above scenario, one would expect a response body with pagination information closely resembling the JSON object below.

{
"data": [
         ... Blog Data
    ],
    "totalPages": 9,
    "currentPageNumber": 2,
    "pageSize": 10,
    "totalRecords": 90
}

• Read more about REST pagination in Spring by clicking here.

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Part 6.1 - Load Dummy Poll Data

• Create a src/main/resource/import.sql file with DML statements for populating the database upon bootstrap. The import.sql should insert at least 15 polls, each with 3 or more options.

  • Below is an example of SQL statements for creating a single poll with only one option.

    • Poll Creation

      insert into poll (poll_id, question) values (1, 'What is your favorite color?');
      

    • Option Creation

      insert into option (option_id, option_value, poll_id) values (1, 'Red', 1);
      

• Restart your application.

• Use Postman to ensure database is populated by import.sql.

Part 6.2 - Spring's Built-in Pagination

• Make use of Spring's built-in page number pagination support by researching org.springframework.data.repository.PagingAndSortingRepository.
• Modify respective Controller methods to handle Pageable arguments.
• Send a GET request to http://localhost:8080/polls?page=0&size=2 via Postman.
• Ensure the response is a JSON object with pagination-specific information.