J4.x:Adding an API to a Joomla Component

Joomla! 

4.0

This page is intended to document how to integrate the Web Services layer introduced in into an existing Joomla component. This assumes that you are using the default Joomla MVC layer.

Web Services integration for weblinks extension as an example

Repository extension: https://github.com/joomla-extensions/weblinks

Pull request: https://github.com/joomla-extensions/weblinks/pull/407

Plugin Code

The point of entry to your component from an API call is a plugin.

The plugin re-routes the API call into the API code that services the request.

In this example an API call to the weblinks component might be

(yourSite)/api/index.php/v1/weblinks

This means your installation file is best represented as a package, pkg_weblinks in this case, so that it can contain not only your original component, but also the required plugin.

1. Create the plugin folder plugins/webservices/weblinks.

Your plugin code goes in a subdirectory of the webservices directory under the plugins directory, in this example plugins/webservices/weblinks.

File system structure

2. In weblinks.php, create the class PlgWebservicesWeblinks.

use Joomla\CMS\Plugin\CMSPlugin;
use Joomla\CMS\Router\ApiRouter;

class PlgWebservicesWeblinks extends CMSPlugin
{
    public function onBeforeApiRoute(&$router)
    {
        $router->createCRUDRoutes('v1/weblinks', 'weblinks', ['component' => 'com_weblinks']);
    }
}

In the onBeforeApiRoute method, register all the routes needed for the webservice.

When Joomla receives an API call it loads the API router which then collects a list of endpoints it should be aware of by running the "onBeforeApiRoute" method in all enabled plugin classes that contain it. Then it can locate the API component relevant to the API endpoint that has been called.

The API code

The router specifies the path for the relevant API code.

This API code is in a folder named "api" off the site root. It is exactly analagous to the "admin" and "site" sections.

In your installation package this code should be included in your component installer because the Joomla installation process automatically creates a section for each installed component there, whether it has any API code or not.

The structure of this section has the same directory pattern as the other extension sections (ie components, modules, plugins).

1. Create the API code folder /api.

File system structure

2. Create the controller class WeblinksController.

The controller is named in the second parameter of the "createCRUDRoutes" method in the plugin.

You can expose more than one output structure by registering more than one route, specifiying a different controller for each structure.

use Joomla\CMS\MVC\Controller\ApiController;

class WeblinksController extends ApiController
{
    protected $contentType = 'weblinks';

    protected $default_view = 'weblinks';
}

Override the following fields:

$contentType - will be used as default for $modelName as well as when outputting response as type object
$default_view - will be used as default for $viewName

3. The display class JsonapiView.php

Extending JsonApiView gives you the same kinds of features that HtmlView does in a usual component view, slightly changed to be appropriate for outputting Json.

NB Although the core class is JsonApiView (uppercase A for Api), your override must have a lowercase a.

The item and list fields to render, as shown below, specify which fields to include in the respective outputs.

use Joomla\CMS\MVC\View\JsonApiView as BaseApiView;

class JsonapiView extends BaseApiView
{
    protected $fieldsToRenderItem = [
        'id',
        'catid',
        'title',
        'alias',
        'url',
        'xreference',
        'tags',
    ];

    protected $fieldsToRenderList = [
        'id',
        'title',
        'alias',
    ];
}

Override the following fields:

$fieldsToRenderItem - array of fields to display a single object
$fieldsToRenderList - array of fields for listing objects

3. Create the manifest file, weblinks.xml

<?xml version="1.0" encoding="utf-8"?>
<extension version="3.1" type="plugin" group="webservices" method="upgrade">
    <name>PLG_WEBSERVICES_WEBLINKS</name>
    <author>Joomla! Project</author>
    <creationDate>August 2017</creationDate>
    <copyright>(C) 2005 - 2019 Open Source Matters. All rights reserved.</copyright>
    <license>GNU General Public License version 2 or later; see LICENSE.txt</license>
    <authorEmail>admin@joomla.org</authorEmail>
    <authorUrl>www.joomla.org</authorUrl>
    <version>4.0.0</version>
    <description>PLG_WEBSERVICES_WEBLINKS_XML_DESCRIPTION</description>
    <files>
         ##FILES##
    </files>
    <languages folder="administrator/language">
         ##LANGUAGE_FILES##
    </languages>
</extension>

4. Create language files with content

As usual, language files can, and should, be supplied; en-GB/plg_webservices_weblinks.ini, en-GB/plg_webservices_weblinks.sys.ini. It may be unnecessary to provide the user language file (".ini"), but content for the system file (".sys.ini") is required, if only for the plugin administration list.

; Joomla! Project
; Copyright (C) 2005 - 2019 Open Source Matters. All rights reserved.
; License GNU General Public License version 2 or later; see LICENSE.txt, see LICENSE.php
; Note : All ini files need to be saved as UTF-8

PLG_WEBSERVICES_WEBLINKS="Web Services - Weblinks"
PLG_WEBSERVICES_WEBLINKS_XML_DESCRIPTION="Used to add weblinks routes to the Web Services API for your website."

Packaging

Provide a package manifest file. In the case of this example, in the file src/administrator/manifests/packages/pkg_weblinks.xml add a description for the webservice plugin

<files>
    ...
    <file type="plugin" id="weblinks" group="webservices">plg_webservices_weblinks.zip</file>
</files>

Categories

1. Add categories support for weblinks webservice. Edit the file src/plugins/webservices/weblinks/weblinks.php

class PlgWebservicesWeblinks extends CMSPlugin
{
    public function onBeforeApiRoute(&$router)
    {
        ...
        $router->createCRUDRoutes(
            'v1/weblinks/categories',
            'categories',
            ['component' => 'com_categories', 'extension' => 'com_weblinks']
        );
    }
}

We use the ready-made component com_categories, and just need to pass the parameter 'extension' => 'com_weblinks'

Fields and Groups

1. Add fields and fields groups support for weblinks webservice. Edit the file src/plugins/webservices/weblinks/weblinks.php

class PlgWebservicesWeblinks extends CMSPlugin
{
    public function onBeforeApiRoute(&$router)
    {
        ...
        $router->createCRUDRoutes(
            'v1/fields/weblinks',
            'fields',
            ['component' => 'com_fields', 'context' => 'com_weblinks.weblink']
        );

        $router->createCRUDRoutes(
            'v1/fields/groups/weblinks',
            'groups',
            ['component' => 'com_fields', 'context' => 'com_weblinks.weblink']
        );
    }
}

2. Override the function save in WeblinksController.

class WeblinksController extends ApiController
{
    ...

    protected function save($recordKey = null)
    {
        $data = (array) json_decode($this->input->json->getRaw(), true);

        foreach (FieldsHelper::getFields('com_weblinks.weblink') as $field)
        {
            if (isset($data[$field->name]))
            {
                !isset($data['com_fields']) && $data['com_fields'] = [];

                $data['com_fields'][$field->name] = $data[$field->name];
                unset($data[$field->name]);
            }
        }

        $this->input->set('data', $data);

        return parent::save($recordKey);
    }

    ...
}

3. Override the functions displayList, displayItem, prepareItem in Weblinks\JsonApiView.

class JsonApiView extends BaseApiView
{
    ...

    public function displayList(array $items = null)
    {
        foreach (FieldsHelper::getFields('com_weblinks.weblink') as $field)
        {
            $this->fieldsToRenderList[] = $field->name;
        }

        return parent::displayList();
    }

    public function displayItem($item = null)
    {
        foreach (FieldsHelper::getFields('com_weblinks.weblink') as $field)
        {
            $this->fieldsToRenderItem[] = $field->name;
        }

        return parent::displayItem();
    }

    protected function prepareItem($item)
    {
        foreach (FieldsHelper::getFields('com_weblinks.weblink', $item, true) as $field)
        {
            $item->{$field->name} = isset($field->apivalue) ? $field->apivalue : $field->rawvalue;
        }

        return parent::prepareItem($item);
    }

    ...
}

Pay attention in function prepareItem to

$field->apivalue

. If the type of the field is complex, we hope that it will return a value for output in the Web Services API component, otherwise we will take

$field->rawvalue

Data

The core functionality renders the data that you would expect from a simple component in the normal web interface. For this, the API defaults to administration data models. However, providing a "Model" section in your API code gives you back the flexibility to construct whatever data shape you want just for your API output. Provide a model for each view with the usual naming conventions.

The system JsonApiView class formats the Json output as three data sets; links, items, and metadata. To change that, override the display class in your own JsonapiView and *don't* call the parent class.

Integration Work Example

NOTE: Remember to enable weblinks webservice plugin!

Weblinks

Get List of Weblinks

curl -X GET /api/index.php/v1/weblinks

Get Single Weblink

curl -X GET /api/index.php/v1/weblinks/{weblink_id}

Delete Weblink

curl -X DELETE /api/index.php/v1/weblinks/{weblink_id}

Create Weblink

curl -X POST -H "Content-Type: application/json" /api/index.php/v1/weblinks -d

{
    "access": "1",
    "alias": "",
    "catid": "8",
    "description": "<p>text</p>",
    "images": {
        "float_first": "",
        "float_second": "",
        "image_first": "",
        "image_first_alt": "",
        "image_first_caption": "",
        "image_second": "",
        "image_second_alt": "",
        "image_second_caption": ""
    },
    "language": "*",
    "metadata": {
        "rights": "",
        "robots": ""
    },
    "metadesc": "",
    "metakey": "",
    "modified": "",
    "params": {
        "count_clicks": "",
        "height": "",
        "target": "",
        "width": ""
    },
    "title": "weblink title",
    "url": "http://somelink.com/",
    "xreference": "xreference"
}

Update Weblink

curl -X PUT -H "Content-Type: application/json" /api/index.php/v1/weblinks/{weblink_id} -d

{
    "catid": "8",
    "description": "<p>some new text</p>",
    "language": "*",
    "title": "new title",
    "url": "http://newsomelink.com/"
}

Categories

Route Weblinks Categories is: "v1/weblinks/categories"

Working with it is similar to Banners Categories.

Fields

Route Fields Weblinks is: "v1/fields/weblinks"

Working with it is similar to Fields Contact.

Groups Fields

Route Groups Fields Weblinks is: "v1/fields/groups/weblinks"

Working with it is similar to Groups Fields Contact.