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JSON and XML views

The JsonView and XmlView let you create JSON and XML responses, and integrate with the Cake\Controller\Component\RequestHandlerComponent.

By enabling RequestHandlerComponent in your application, and enabling support for the json and/or xml extensions, you can automatically leverage the new view classes. JsonView and XmlView will be referred to as data views for the rest of this page.

There are two ways you can generate data views. The first is by using the _serialize key, and the second is by creating normal template files.

Enabling Data Views in Your Application

Before you can use the data view classes, you’ll first need to load the Cake\Controller\Component\RequestHandlerComponent in your controller:

public function initialize()
{
    ...
    $this->loadComponent('RequestHandler');
}

This can be done in your AppController and will enable automatic view class switching on content types. You can also set the component up with the viewClassMap setting, to map types to your custom classes and/or map other data types.

You can optionally enable the json and/or xml extensions with Routing File Extensions. This will allow you to access the JSON, XML or any other special format views by using a custom URL ending with the name of the response type as a file extension such as http://example.com/articles.json.

By default, when not enabling Routing File Extensions, the request, the Accept header is used for, selecting which type of format should be rendered to the user. An example Accept format that is used to render JSON responses is application/json.

Using Data Views with the Serialize Key

The _serialize key is a special view variable that indicates which other view variable(s) should be serialized when using a data view. This lets you skip defining template files for your controller actions if you don’t need to do any custom formatting before your data is converted into json/xml.

If you need to do any formatting or manipulation of your view variables before generating the response, you should use template files. The value of _serialize can be either a string or an array of view variables to serialize:

namespace App\Controller;

class ArticlesController extends AppController
{
    public function initialize()
    {
        parent::initialize();
        $this->loadComponent('RequestHandler');
    }

    public function index()
    {
        // Set the view vars that have to be serialized.
        $this->set('articles', $this->paginate());
        // Specify which view vars JsonView should serialize.
        $this->set('_serialize', 'articles');
    }
}

You can also define _serialize as an array of view variables to combine:

namespace App\Controller;

class ArticlesController extends AppController
{
    public function initialize()
    {
        parent::initialize();
        $this->loadComponent('RequestHandler');
    }

    public function index()
    {
        // Some code that created $articles and $comments

        // Set the view vars that have to be serialized.
        $this->set(compact('articles', 'comments'));

        // Specify which view vars JsonView should serialize.
        $this->set('_serialize', ['articles', 'comments']);
    }
}

Defining _serialize as an array has added the benefit of automatically appending a top-level <response> element when using XmlView. If you use a string value for _serialize and XmlView, make sure that your view variable has a single top-level element. Without a single top-level element the Xml will fail to generate.

Using a Data View with Template Files

You should use template files if you need to do some manipulation of your view content before creating the final output. For example if we had articles, that had a field containing generated HTML, we would probably want to omit that from a JSON response. This is a situation where a view file would be useful:

// Controller code
class ArticlesController extends AppController
{
    public function index()
    {
        $articles = $this->paginate('Articles');
        $this->set(compact('articles'));
    }
}

// View code - src/Template/Articles/json/index.ctp
foreach ($articles as &$article) {
    unset($article->generated_html);
}
echo json_encode(compact('articles'));

You can do more complex manipulations, or use helpers to do formatting as well. The data view classes don’t support layouts. They assume that the view file will output the serialized content.

Note

As of 3.1.0 until 3.5.0, AppController in the application skeleton automatically added '_serialize' => true to all XML/JSON requests. You will need to remove this code from the beforeRender callback or set '_serialize' => false in your controller’s action if you want to use view files.

Creating XML Views

class XmlView

By default when using _serialize the XmlView will wrap your serialized view variables with a <response> node. You can set a custom name for this node using the _rootNode view variable.

The XmlView class supports the _xmlOptions variable that allows you to customize the options used to generate XML, e.g. tags vs attributes.

An example of using XmlView would be to generate a sitemap.xml. This document type requires that you change _rootNode and set attributes. Attributes are defined using the @ prefix:

public function sitemap()
{
    $pages = $this->Pages->find();
    $urls = [];
    foreach ($pages as $page) {
        $urls[] = [
            'loc' => Router::url(['controller' => 'Pages', 'action' => 'view', $page->slug, '_full' => true]),
            'lastmod' => $page->modified->format('Y-m-d'),
            'changefreq' => 'daily',
            'priority' => '0.5'
        ];
    }

    // Define a custom root node in the generated document.
    $this->set('_rootNode', 'urlset');
    $this->set([
        // Define an attribute on the root node.
        '@xmlns' => 'http://www.sitemaps.org/schemas/sitemap/0.9',
        'url' => $urls
    ]);
    $this->set('_serialize', ['@xmlns', 'url']);
}

Creating JSON Views

class JsonView

The JsonView class supports the _jsonOptions variable that allows you to customize the bit-mask used to generate JSON. See the json_encode documentation for the valid values of this option.

For example, to serialize validation error output of CakePHP entities in a consistent form of JSON do:

// In your controller's action when saving failed
$this->set('errors', $articles->errors());
$this->set('_jsonOptions', JSON_FORCE_OBJECT);
$this->set('_serialize', ['errors']);

JSONP Responses

When using JsonView you can use the special view variable _jsonp to enable returning a JSONP response. Setting it to true makes the view class check if query string parameter named “callback” is set and if so wrap the json response in the function name provided. If you want to use a custom query string parameter name instead of “callback” set _jsonp to required name instead of true.

Example Usage

While the RequestHandlerComponent can automatically set the view based on the request content-type or extension, you could also handle view mappings in your controller:

// src/Controller/VideosController.php
namespace App\Controller;

use App\Controller\AppController;

// Prior to 3.6 use Cake\Network\Exception\NotFoundException
use Cake\Http\Exception\NotFoundException;

class VideosController extends AppController
{
    public function export($format = '')
    {
        $format = strtolower($format);

        // Format to view mapping
        $formats = [
          'xml' => 'Xml',
          'json' => 'Json',
        ];

        // Error on unknown type
        if (!isset($formats[$format])) {
            throw new NotFoundException(__('Unknown format.'));
        }

        // Set Out Format View
        $this->viewBuilder()->className($formats[$format]);

        // Get data
        $videos = $this->Videos->find('latest');

        // Set Data View
        $this->set(compact('videos'));
        $this->set('_serialize', ['videos']);

        // Set Force Download
        // Prior to 3.4.0
        // $this->response->download('report-' . date('YmdHis') . '.' . $format);
        return $this->response->withDownload('report-' . date('YmdHis') . '.' . $format);
    }
}