Routing#

Routing is the process of mapping URL's to Controller and actions. In the introduction we defined a new custom route for our TeamController mapping any teams URL to our TeamController

These routes by standard, go into a routes.yml file in your applications _config folder alongside your other Configuration information.

# app/_config/routes.yml
---
Name: approutes
After:
  - '#rootroutes'
  - '#coreroutes'
---
SilverStripe\Control\Director:
  rules:
    'teams//$Action/$ID/$Name': 'App\Control\TeamController'
    'player/': 'App\Control\PlayerController'
    '': 'App\Control\HomeController'

Parameters#

SilverStripe\Control\Director:
  rules:
    'teams//$Action/$ID/$Name': 'App\Control\TeamController'

This route has defined that any URL beginning with team should create, and be handled by a TeamController instance.

It also contains 3 parameters or params for short. $Action, $ID and $Name. These variables are placeholders which will be filled when the user makes their request. Request parameters are available on the HTTPRequest object and able to be pulled out from a controller using $this->getRequest()->param($name).

Here is what those parameters would look like for certain requests

// GET /teams/

print_r($this->getRequest()->params());

// Array
// (
//   [Action] => null
//   [ID] => null
//   [Name] => null
// )

// GET /teams/players/

print_r($this->getRequest()->params());

// Array
// (
//   [Action] => 'players'
//   [ID] => null
//   [Name] => null
// )

// GET /teams/players/1

print_r($this->getRequest()->params());

// Array
// (
//   [Action] => 'players'
//   [ID] => 1
//   [Name] => null
// )

You can also fetch one parameter at a time.

// GET /teams/players/1/

echo $this->getRequest()->param('ID');
// returns '1'

URL patterns#

The RequestHandler class will parse all rules you specify against the following patterns. The most specific rule will be the one followed for the response.

'teams/$Action/$ID/$OtherID': 'App\Control\TeamController'

# /teams/
# /teams/players/
# /teams/

Standard URL handler syntax. For any URL that contains 'team' this rule will match and hand over execution to the matching controller. The TeamController is passed an optional action, id and other id parameters to do any more decision making.

'teams/$Action!/$ID!/': 'App\Control\TeamController'

This does the same matching as the previous example, any URL starting with teams will look at this rule but both $Action and $ID are required. Any requests to team/ will result in a 404 error rather than being handed off to the TeamController.

'admin/help//$Action/$ID: 'AdminHelp'

Match an URL starting with /admin/help/, but don't include /help/ as part of the action (the shift point is set to start parsing variables and the appropriate controller action AFTER the //).

Wildcard URL patterns#

As of Silverstripe CMS 4.6 there are two wildcard patterns that can be used. $@ and $*. These parameters can only be used at the end of a URL pattern, any further rules are ignored.

Inspired by bash variadic variable syntax there are two ways to capture all URL parameters without having to explicitly specify them in the URL rule.

Using $@ will split the URL into numbered parameters ($1, $2, ..., $n). For example:

namespace App\Control;

use SilverStripe\Control\Controller;

class StaffController extends Controller
{
    private static $url_handlers = [
        'staff/$@' => 'index',
    ];

    public function index($request)
    {
        // GET /staff/managers/bob
        // managers
        $request->latestParam('$1');
        // bob
        $request->latestParam('$2');
    }
}

Alternatively, if access to the parameters is not required in this way then it is possible to use $* to match all URL parameters but not collect them in the same way:

namespace App\Control;

use SilverStripe\Control\Controller;

class StaffController extends Controller
{
    private static $url_handlers = [
        'staff/$*' => 'index',
    ];

    public function index($request)
    {
        // GET /staff/managers/bob
        // managers/bob
        $request->remaining();
    }
}

URL handlers#

In the above example the URLs were configured using the Director rules in the routes.yml file. Alternatively you can specify these in your Controller class via the $url_handlers static array. This array is processed by the RequestHandler at runtime once the Controller has been matched.

This is useful when you want to provide custom actions for the mapping of teams/*. Say for instance we want to respond coaches, and staff to the one controller action payroll.

// app/src/Control/TeamController.php
namespace App\Control;

use SilverStripe\Control\Controller;

class TeamController extends Controller
{
    private static $allowed_actions = [
        'payroll',
    ];

    private static $url_handlers = [
        'staff/$ID/$Name' => 'payroll',
        'coach/$ID/$Name' => 'payroll',
    ];

    // ...
}

The syntax for the $url_handlers array users the same pattern matches as the YAML configuration rules.

Now let’s consider a more complex example from a real project, where using $url_handlers is mandatory. In this example, the URLs are of the form http://example.org/feed/go/, followed by 5 parameters. The PHP controller class specifies the URL pattern in $URL_handlers. Notice that it defines 5 parameters.

namespace App\Control;

use SilverStripe\CMS\Controllers\ContentController;

class FeedController extends ContentController
{
    private static $allowed_actions = ['go'];
    private static $url_handlers = [
        'go/$UserName/$AuthToken/$Timestamp/$OutputType/$DeleteMode' => 'go',
    ];

    public function go()
    {
        $this->validateUser(
            $this->getRequest()->param('UserName'),
            $this->getRequest()->param('AuthToken')
        );
        /* more processing goes here */
    }
}

The YAML rule, in contrast, is simple. It needs to provide only enough information for the framework to choose the desired controller.

SilverStripe\Control\Director:
  rules:
    'feed': 'App\Control\FeedController'

Root URL handlers#

In some cases, the Director rule covers the entire URL you intend to match, and you simply want the controller to respond to a 'root' request. This request will automatically direct to an index() method if it exists on the controller, but you can also set a custom method to use in $url_handlers with the '/' key:

namespace App\Control;

use SilverStripe\Control\Controller;

class BreadAPIController extends Controller
{
    private static $allowed_actions = [
        'getBreads',
        'createBread',
    ];

    private static $url_handlers = [
        'GET /' => 'getBreads',
        'POST /' => 'createBread',
    ];

    // ...
}

Nested request handlers#

Nested RequestHandler routing is used extensively in the CMS and is used to create URL endpoints without YAML configuration. Nesting is done by returning a RequestHandler from an action method on another RequestHandler, usually a Controller.

RequestHandler is the base class for other classes that can handle HTTP requests such as Controller, FormRequestHandler (used by Form) and FormField.

How it works#

Director::handleRequest() begins the URL parsing process by parsing the start of the URL and workng out which request handler to use by looking in routes set in YAML config under Director.rules.

When a request handler matching the first portion of the URL is found, the handleRequest() method on the matched request handler is called. This passes control to the matched request handler and the next portion of the URL is processed.

From there regular request handling occurs and the URL will be checked to see if it matches $allowed_actions on the RequestHandler, possibly routed via $url_handlers. If an $allowed_action (i.e. method on the RequestHandler) is matched and that method returns a request handler, then control will be passed to this nested request handler and the next portion of the URL is processed.

Example of a nested request handler being returned in an action method#

Using the code below, navigating to the URL /one/two/hello will return a response with a body of "hello"

// app/_config/routes.yml
SilverStripe\Control\Director:
  rules:
    'one': 'App\Control\RequestHandlerOne'

// app/src/Control/RequestHandlerOne.php
namespace App\Control;

use SilverStripe\Control\Controller;
use SilverStripe\Control\HTTPRequest;

class RequestHandlerOne extends Controller
{
    // ...
    private static $allowed_actions = [
        'two',
    ];

    public function two(HTTPRequest $request)
    {
        return RequestHandlerTwo::create();
    }
}

// app/src/Control/RequestHandlerTwo.php
namespace App\Control;

use SilverStripe\Control\Controller;
use SilverStripe\Control\HTTPRequest;
use SilverStripe\Control\HTTPResponse;

class RequestHandlerTwo extends Controller
{
    // ...
    private static $allowed_actions = [
        'hello',
    ];

    public function hello(HTTPRequest $request)
    {
        return HTTPResponse::create()->setBody('hello');
    }
}

How RequestHandler and Form work together#

Form does not extend RequestHandler, instead it implements the HasRequestHandler interface which defines a method getRequestHandler(). Form::getRequestHandler() returns a FormRequestHandler which is a subclass of RequestHandler.

Request handlers and implementors of HasRequestHandler are treated the same because they will both end up calling handleRequest() on the appropriate request handler.

The FormRequestHandler.url_handlers configuration property includes an entry 'field/$FieldName!' => 'handleField' which allows it to handle requests to form fields on the form. FormRequestHandler::handleField() will find the form field matching $FieldName and return it. Control is then passed to the returned form field.

FormField extends RequestHandler, which means that form fields are able to handle HTTP requests and they have their own $allowed_actions configuration property. This allows form fields to define their own AJAX endpoints without having to rely on separately routed RequestHandler implementations.

Example of an AJAX form field that uses nested request handlers#

The AJAX request performed by the "Viewer groups" dropdown in asset admin has an endpoint of /admin/assets/fileEditForm/{FileID}/field/ViewerGroups/tree?format=json

That URL ends up passing the request through a series of nested request handlers, which is detailed in the steps below. Unless otherwise stated, the handleRequest() method is called on the class that has control. Control starts with Director.

1. admin matches a rule in the Director.rules YAML configuration property and control is passed to AdminRootController
2. assets matches the AssetAdmin.url_segment property that has a value of assets and control is passed to AssetAdmin
3. fileEditForm/{FileID} matches 'fileEditForm/$ID' => 'fileEditForm' in AssetAdmin.url_handlers so the AssetAdmin::fileEditForm() method is called
4. AssetAdmin::fileEditForm() returns a Form scaffolded for the File matching the ID and control is passed to the returned Form
5. Form::getRequestHandler() will be called on the Form and control is passed to the FormRequestHandler that is returned
6. field/ViewerGroups matches 'field/$FieldName!' => 'handleField' in FormRequestHandler.url_handlers, so FormRequestHandler::handleField() is called
7. FormRequestHandler::handleField() finds the ViewerGroups field in the Form which is a TreeMultiselectField that extends TreeDropdownField and control is passed to the field
8. tree matches tree in TreeDropdownField.allowed_actions, so TreeDropdownField::tree() is called
9. TreeDropdownField::tree() returns an HTTPResponse with its body containing JSON

Related lessons#

• Creating filtered views
• Controller actions / DataObjects as pages

Links#

• Controller API documentation
• Director API documentation
• Example routes: framework
• Example routes: CMS