Data Sprunjing

Once your users log in, you'll probably want to have them interact with your data models in some way. One very common UI pattern is to present a list or table of data to a user, and allow them to sort, paginate, and search/filter the data. For example, the tablesorter and select2 plugins follow this pattern.

In cases where you could potentially have thousands of retrievable rows, it would be unwise to try to send them all to the client and then use Javascript to handle searching and sorting. This would make response times much slower, and place an excessive burden on the client's browser - not a good user experience!

Instead it's best to perform sorting, filtering, and pagination (which we will collectively refer to as constraints) on the server, directly in your SQL queries. The client passes in a set of parameters through your API endpoints to indicate how the data should be constrained. For example:

GET http://localhost/userfrosting/public/api/users?size=5&page=0&sorts%5Bname%5D=asc

This tells the server that we want a list of users sorted by their name, in ascending order (sorts[name]=asc). We then want them chunked into blocks of 5 results at a time (size=5), and for this request we want the first chunk (page=0).

Building queries that can handle all of these request parameters correctly, for every one of your endpoints, can be surprisingly tricky and very tedious. This is why UserFrosting introduces the Sprunjer, allowing you to easily define rules for how clients can retrieve constrained results from your database.

Sprunje parameters

Every Sprunje can accept the following parameters. Typically, they are passed in as a query string in a GET request, and then passed as the second argument in your Sprunje's constructor.

  • sorts: an associative array of field names mapped to sort directions. Sort direction can be either asc or desc.
  • filters: an associative array of field names mapped to queries. For example, name: Attenb will search for names that contain "Attenb."
  • size: either an integer specifying the maximum number of results to return, or all to retrieve all results.
  • page: an integer specifying the page (chunk) number to retrieve, when size is specified. For example, to retrieve the first chunk, set page to 0.
  • format => the format in which data should be returned. Can be either json or csv.

Defining a Sprunje

By implementing a custom Sprunje class, you can pass parameters directly from the client request and they will be used to safely construct the appropriate query.

A custom Sprunje is simply a class that extends the base UserFrosting\Sprinkle\Core\Sprunje\Sprunje class. At the minimum you must define the name property and implement the baseQuery class, which specifies the Eloquent query to be performed before any additional constraints are applied. By convention, you should place your Sprunje classes in src/Sprunje/ in your Sprinkle.

OwlSprunje.php

<?php
namespace UserFrosting\Sprinkle\Site\Sprunje;

use UserFrosting\Sprinkle\Core\Facades\Debug;
use UserFrosting\Sprinkle\Core\Sprunje\Sprunje;

use UserFrosting\Sprinkle\Site\Database\Models\Owl;

class OwlSprunje extends Sprunje
{
    protected $name = 'owls';

    /**
     * Set the initial query used by your Sprunje.
     */
    protected function baseQuery()
    {
        $instance = new Owl();

        // Alternatively, if you have defined a class mapping, you can use the classMapper:
        // $instance = $this->classMapper->createInstance('owl');

        return $instance->newQuery();
    }
}

baseQuery should return an instance of a "queriable" class. Queriable classes include 'Illuminate\Database\Eloquent\Builder, 'Illuminate\Database\Query\Builder, and Illuminate\Database\Eloquent\Relations\Relation (and child classes of these). If you want your Sprunje to automatically join other tables or load related objects, baseQuery is a good place to do this.

Sorts and filters

By default, Sprunje will try to match the field names in the sorts and filters query parameters to column names in your Eloquent query. Sorts are automatically transformed into orderBy('fieldName', 'sortDirection') clauses, and filters are transformed into where('fieldName', 'like', '%$value%') clauses.

However, before you can sort or filter on a particular column name, you must add it to the $sortable and $filterable members of your Sprunje class first:

<?php
namespace UserFrosting\Sprinkle\Site\Sprunje;

use UserFrosting\Sprinkle\Core\Facades\Debug;
use UserFrosting\Sprinkle\Core\Sprunje\Sprunje;

class OwlSprunje extends Sprunje
{
    protected $sortable = [
        'name',
        'species'
    ];

    protected $filterable = [
        'name',
        'species'
    ];
    ...
}

This whitelisting is done to prevent consumers of your API from sorting/filtering on arbitrary columns, which could reveal potentially sensitive information. For example, even if you don't return the actual value of a column in your result set (e.g., is_admin), one could still determine which users are admins, for example, by filtering based on is_admin=1. Whitelisting ensures that this cannot happen.

Both sorts and filters can accept multiple values separated by ||, which will cause your Sprunje to return rows that match any of the values.

Using your Sprunje

With your Sprunje defined, you can use the toResponse method in your controller to automatically append the query results to the response:

    /**
     * Returns a list of Owls
     *
     * Generates a list of owls, optionally paginated, sorted and/or filtered.
     * This page requires authentication.
     * Request type: GET
     */
    public function getList($request, $response, $args)
    {
        // GET parameters
        $params = $request->getQueryParams();

        /** @var UserFrosting\Sprinkle\Account\Authorize\AuthorizationManager */
        $authorizer = $this->ci->authorizer;

        /** @var UserFrosting\Sprinkle\Account\Database\Models\User $currentUser */
        $currentUser = $this->ci->currentUser;

        // Access-controlled page
        if (!$authorizer->checkAccess($currentUser, 'uri_owls')) {
            throw new ForbiddenException();
        }

        /** @var UserFrosting\Sprinkle\Core\Util\ClassMapper $classMapper */
        $classMapper = $this->ci->classMapper;

        $sprunje = new OwlSprunje($classMapper, $params);

        // Be careful how you consume this data - it has not been escaped and contains untrusted user-supplied content.
        // For example, if you plan to insert it into an HTML DOM, you must escape it on the client side (or use client-side templating).
        return $sprunje->toResponse($response);
    }

Supposing that we make a request like GET http://localhost/userfrosting/public/api/owls?size=5&page=0&sorts%5Bgenus%5D=asc, we might get a response like:

{
    "count": 5,
    "count_filtered": 5,
    "rows": [
        {
            "id": 11,
            "name": "slasher",
            "genus": "Bubo"
        },
        {
            "id": 8,
            "name": "shredder",
            "genus": "Megascops"
        },
        {
            "id": 3,
            "name": "harold",
            "genus": "Phodilus"
        },
        {
            "id": 1,
            "name": "fluffers",
            "genus": "Tyto"
        },
        {
            "id": 2,
            "name": "kevin",
            "genus": "Tyto"
        }
    ]
}

Notice that when retrieving data in JSON format (default), the response is an array containing three keys: count, count_filtered, and rows. count contains the total number of results before any filters or pagination were applied. count_filtered contains the number of results found after filtering, but before pagination was applied. Finally, rows contains the array of results itself, with all constraints applied.

Custom sorts and filters

The default sorting/filtering capabilities are great, but in some cases you may want to customize the behavior for certain columns, or even define constraints that don't map directly to a column name.

To do this, you can define custom methods in your Sprunje:

    /**
     * Filter LIKE the genus OR species
     *
     * @param Builder $query
     * @param mixed $value
     * @return $this
     */
    protected function filterScientificName($query, $value)
    {
        $query->like('genus', $value)
                ->orLike('species', $value);
        return $this;
    }

The method name should consist of the field name (converted to StudlyCase), prefixed with filter or sort.

Thus, in this example a request parameter of filters[scientific_name]=mega will invoke the filterScientificName method in your Sprunje.

Custom data transformations

Sometimes, you will want to transform the dataset after executing the query, but before returning the results to the client. For example, you might want to remove the password field from a list of users. To have your Sprunje do this every time it is invoked, simply implement the applyTransformations method in your Sprunje:

// In UserSprunje.php

protected function applyTransformations($collection)
{
    // Exclude password field from results
    $collection->transform(function ($item, $key) {
        unset($item['password']);
        return $item;
    });

    return $collection;
}

Extending a Sprunje query

You might want to further modify your Sprunje's base query in certain endpoints. For example, you might want to retrieve the owner of each Owl in your result set, but only in your /api/owls endpoint. In this case, you can modify your Sprunje by passing a callback to the extendQuery method:

// In OwlController::getList method

$sprunje = new OwlSprunje($classMapper, $params);
$sprunje->extendQuery(function ($query) {
    return $query->with('owner');
});

Sprunje lists

Sprunjes can also be used to enumerate a unique list of values for fields in the target model. This is useful, for example, when you want to present a dropdown list of values for the user to choose among. To make a field listable, simply add it to a listable member variable in your Sprunje class:

<?php
namespace UserFrosting\Sprinkle\Site\Sprunje;

use UserFrosting\Sprinkle\Core\Facades\Debug;
use UserFrosting\Sprinkle\Core\Sprunje\Sprunje;

class OwlSprunje extends Sprunje
{
    protected $listable = [
        'species'
    ];

    ...

An array mapping each listable field to a list of possible values can be obtained by calling the getListable method on your Sprunje. For each listable field, by default getListable will look for a corresponding table column of the same name, and generate sub-arrays containing value and text fields, each of which will contain the given value:

"listable": {
    "species": [
        {
            "value": "Athene",
            "text": "Athene"
        },
        {
            "value": "Bubo",
            "text": "Bubo"
        },
        {
            "value": "Glaucidium",
            "text": "Glaucidium"
        },
        {
            "value": "Megascops",
            "text": "Megascops"
        },
        {
            "value": "Tyto",
            "text": "Tyto"
        }
    ]
}

Of course you can override the default listing behavior for a field by defining a custom method. This method must consist of the field name (converted to StudlyCase) prefixed with list:

/**
 * Return a list of possible user statuses.
 *
 * @return array
 */
protected function listStatus()
{
    return [
        [
            'value' => 'active',
            'text' => Translator::translate('ACTIVE')
        ],
        [
            'value' => 'unactivated',
            'text' => Translator::translate('UNACTIVATED')
        ],
        [
            'value' => 'disabled',
            'text' => Translator::translate('DISABLED')
        ]
    ];
}

Etymology

If you're wondering where the term "Sprunje" comes from: