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 Specific Information

Pagination-specific information includes
- total number of records
- total number of pages
- current page number
- page size

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Pagination Data

In the above scenario, one would expect a response body with pagination infromation 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.