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Validating domain objects

We have discussed both Extbase and Fluid in some detail, but have spent very little time discussing the domain and how we go about ensuring its consistency. We often assume that domain objects are consistent and adhere to our rules at all times. Unfortunately, this is not achieved automatically. So it is important to define these rules explicitly. In the blog example for example we can create the following rules:

• The field username and password of the user object must have at least 5 characters. Furthermore the username must not contain special characters.

• The field email of the user object must contain a valid email address.

These rules must apply at all times for the user object. A user object is only valid if it complies to these validation rules. These rules are called invariants because they must be valid during the entire lifetime of the object.

At the beginning of your project, it is important to consider which invariants your domain objects will consist of. The next stage is to add these invariants to Extbase in an appropriate way. Extbase provides validators for checking the invariants - these are PHP classes in which the invariants are implemented in code.

We will show you in the following example how you can use a validator for the checking of invariants and how you can give the user the ability to correct an error if and when it occurs.

Validators for checking of Invariants

A validator is a PHP class that has to check a certain invariant. All validators that are used in Extbase extensions have to implement the interface \TYPO3\CMS\Extbase\Validation\Validator\ValidatorInterface. The interface requires validators to implement two methods:

• validate($value)

• getOptions()

The main method is validate, which is called by the framework. The value which is to be validated is passed along to said method and it's the validator's job to check if that value is valid.

Note

Although the interface states, that the method validate should return a \TYPO3\CMS\Extbase\Error\Result object, it's not common practice to do so because most people who create custom validators extend the class \TYPO3\CMS\Extbase\Validation\Validator\AbstractValidator.

This enables you to call the addError()` method and let the abstract validator take care of returning a proper result object to the validation framework.

If the logic of your validator allows for loose/variable validation checks, validator options might come in handy. Extbase ships with a StringLength validator which offers the options minimum and maximum that let you define the string length the validator should use to check the incoming value against.

Tip

You will find the complete reference of the ValidatorInterface in the Validation API.

For example, a validator which checks whether the passed string is an email address looks like this:

public function validate($value)
{
    if (!is_string($value) || !$this->validEmail($value)) {
        $this->addError(
            $this->translateErrorMessage(
                'validator.emailaddress.notvalid',
                'extbase'
            ), 1221559976);
    }
}

protected function validEmail($emailAddress)
{
    return \TYPO3\CMS\Core\Utility\GeneralUtility::validEmail($emailAddress);
}

If $value is neither a string nor a valid email address, the validator adds an error by calling $this->addError().

Tip

The method addError() expects an error message and an error code. The latter should be unique, therefore we recommend to use the UNIX timestamp of the creation time of the source code. With the help of the error code the error can be definitely identified, for example in bug reports.

By default, Extbase will not call your validator if the value to validate is empty. This is configured through the property $acceptsEmptyValues which is set to true by default.

In the package \TYPO3\CMS\Extbase\Validation\Validator\* Extbase offers many validators for default requirements like the validation of emails, numbers and strings.

When does validation take place?

Domain objects in Extbase are validated only at one point in time: When they get inserted into a controller action. With the help of figure 9-1 we can show what happens before the action is called.

Figure 9-1: Data flow of a request before the action is called

When a user sends a request, Extbase first determines which action within the controller is responsible for this request. As Extbase knows the names and types of the arguments of the action it can create objects from the incoming data. This operation will be described in detail in the section "Argument mapping" later on. Now the main step for us is as follows: The created objects are to be validated, that is the invariants are to be checked. If all arguments are successfully validated, the requested action of the extension is called and it can continue processing the given objects. For example, it might pass it to the view ready for displaying.

Tip

Certainly it would be helpful if the validation is also be done during the persisting of the objects to the database. At the moment it is not done since the data is stored in the database after sending the answer back to the browser. Therefore the user could not be informed in case of validating errors. In the meantime a second validating when persisting the objects is built into FLOW, so this will be expected in Extbase in the medium term.

When an error occurs during validation, the method errorAction() of the current controller is called. The default errorAction() redirects the user to the last used form when possible, in order to give them a chance to correct the errors.

Tip

You may ask how the errorAction() knows which form was the last displayed one. This information is created by the form ViewHelper. He adds automatically the property __referrer to every generated form, which contains information about the current extension, controller and action combination. This data can be used by the errorAction() to display the erroneous form again.

Registering validators

Now we know how validators are working and when they are called. However we have to connect our domain model with the validators to define which part of the model is has to be checked by which validator. Therefore there are three possibilities which we define in the following:

• validating in the domain model with annotations

• validating in the domain model with our own validator class

• validating of controller arguments

Validating in the domain model with annotations

In most cases it is sufficient to validate the properties of a domain object separately. When all properties are validated with success the complete domain object is also successfully validated. When a property can not be validated, the overall validation of the domain object fails.

To define how a property of our domain object should be validated we use annotations inside our source code. Annotations are machine readable "annotations" in the source code that are placed in comment blocks and start with the character @.

For the validation the @TYPO3\CMS\Extbase\Annotation\Validate annotation is available. With it we can specify which validator is to be used for checking the annotated property. Let us take a look at this using part of the domain model Post inside the blog example:

<?php
namespace MyVendor\BlogExample\Domain\Model;

class Post extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
{
    /**
     * @var string
     * @TYPO3\CMS\Extbase\Annotation\Validate("StringLength", options={"minimum": 3, "maximum": 50})
     */
    protected $title;

    /**
     * @var string
     */
    protected $content;
}

With the line @TYPO3\CMS\Extbase\Annotation\Validate("StringLength", options={"minimum": 3, "maximum": 50}) the validator for the property $title is specified. In parenthesis the parameters for the validator are also specified. In our case we make sure that a title of a blog post is never shorter than three characters and will never be longer than 50 characters.

Which validator class is to be used? Extbase looks for a validator class using \TYPO3\CMS\Extbase\Validation\Validator\*ValidatorName*Validator. Using the above given annotation @TYPO3\CMS\Extbase\Annotation\Validate("StringLength") the validator \TYPO3\CMS\Extbase\Validation\Validator\StringLengthValidator is used.

When you have created your own validator to check the invariants you can use it in the @TYPO3\CMS\Extbase\Annotation\Validate annotation using the full class name, like shown in the following example:

<?php
namespace MyVendor\BlogExample\Domain\Model;

class Post extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
{
    /**
     * @var string
     * @TYPO3\CMS\Extbase\Annotation\Validate("MyVendor\BlogExample\Domain\Validator\TitleValidator")
     */
    protected $title;

    /**
     * @var string
     */
    protected $content;
}

Here we validate the property $title with the \MyVendor\BlogExample\Domain\Validator\TitleValidator. This validator class now can check any invariants. For example, the validator shown in the following listing checks whether the title of a blog post is always built using the convention Maintopic: Title:

<?php

namespace MyVendor\BlogExample\Domain\Validator;

use TYPO3\CMS\Extbase\Validation\Validator\AbstractValidator;

class TitleValidator extends AbstractValidator
{
   protected function isValid($value)
   {
      // $value is the title string
      if (count(explode(':', $value)) >= 2) {
         return;
      }
      $this->addError('The title was not of the type [Topic]:[Title].', 1221563773);
   }
}

Now you have seen how you can validate particular properties of the domain model. The next section shows to you, how complex domain objects are to be validated.

Validating in the domain model with your own validator class

The ability to register validators in the model are especially useful when individual properties of the model need to be validated. However, sometimes it is necessary to validate the relationship between two or more properties of a model class. For example for a user registration it is reasonable that in the user object the property $password and $passwordConfirmed exists which should be identical. Therefore the individual validators for $password respectively $passwordConfirmation can not help, because they have no access to each other. You need a option to validate a domain object as a whole.

For this you can create your own validator class for every object in the domain model which validates the object as a whole and with it has access to all object properties where possible.

This is the correct naming convention. If you need a validator for the class \MyVendor\ExtbaseExample\Domain\Model\User it must be implemented in the class \MyVendor\ExtbaseExample\Domain\Validator\UserValidator. The name of the validator for a model object is incidental by replacing the namespace Model with Validator and also append Validator. When following the naming convention the validator is automatically called when it exists.

Equipped with this knowledge we can implement the UserValidator which compares $password with $passwordConfirmation. At first we must check if the given object is of the type user - after all the validator can be called with any object and has to add an error in such case:

<?php
namespace MyVendor\ExtbaseExample\Domain\Validator;

class UserValidator extends \TYPO3\CMS\Extbase\Validation\Validator\AbstractValidator
{
    public function validate($user)
    {
        if (! $user instanceof \MyVendor\ExtbaseExample\Domain\Model\User) {
            $this->addError('The given Object is not a User.', 1262341470);
        }
    }
}

If $user is not an instance of the user object an error message is directly created with addError(). The validator does not validate the object any further.

Tip

The method addError() gets two parameters - the first is an error message string while the second is an error number. The Extbase developers always uses the current UNIX timestamp when calling addError(). By this it is secured that the validation errors can be unique identified.

Now we have created the foundation of our validator and can start with the proper implementation of it - the check for equality between the passwords. This is made quickly:

<?php
namespace MyVendor\ExtbaseExample\Domain\Validator;

class UserValidator extends \TYPO3\CMS\Extbase\Validation\Validator\AbstractValidator
{
    public function validate($user)
    {
        if (! $user instanceof \MyVendor\ExtbaseExample\Domain\Model\User) {
            $this->addError('The given Object is not a User.', 1262341470);
            return;
        }
        if ($user->getPassword() !== $user->getPasswordConfirmation()) {
            $this->addError('The passwords do not match.', 1262341707);
        }
    }
}

Because we have access to the complete object the checking for equality of $password and $passwordConfirmation is very straightforward.

Now we have got to know two possibilities how validators can be registered for our domain objects: directly in the model via @TYPO3\CMS\Extbase\Annotation\Validate annotation for single properties and for complete domain objects with an own validator class.

The illustrated validators until now are always executed when a domain model is given as parameter to a controller action - that is for all actions. Sometimes it is desired to initiate the validation only when calling special actions. How this can be done we will see in the next section.

Validating of controller arguments

If you want to validate a domain object only when calling a special action you have to define validators for individual arguments. Therefore a slightly modified form of the @TYPO3\CMS\Extbase\Annotation\Validate annotation can be used which is set in the comment block of the controller action. It has the format @TYPO3\CMS\Extbase\Annotation\Validate *[variablename] [validators]*, in the example below it is $pageName \MyVendor\MyExtension\Domain\Validator\PagenameValidator:

/**
 * Creates a new page with a given name.
 *
 * @param string $pageName THe name of the page which should be created.
 * @TYPO3\CMS\Extbase\Annotation\Validate("MyVendor\MyExtension\Domain\Validator\PageNameValidator", param="pageName")
 */
public function createPageAction($pageName)
{
    // ...
}

Here the parameter $pageName is checked with its own validator.

Interaction of validators

Now you know three possibilities how validators are to be registered. For an argument of an action the following validators are called:

• The data types of the (primitive) arguments are checked. When a parameter is defined with @param float as a floating number then the validator checks this. When you want to disable the type validation for an argument, you have to declare the type as mixed.

• All @TYPO3\CMS\Extbase\Annotation\Validate annotations of the domain model are evaluated.

• The validator class of the domain object is called when it exists.

• More validators that are defined in the action with @TYPO3\CMS\Extbase\Annotation\Validate are called.

Lets have a look at the interaction once more with an example:

/**
 * Creates a website user for the given page name.
 *
 * @param string $pageName The name of the page where the user should be created.
 * @param \MyVendor\ExtbaseExample\Domain\Model\User $user The user which should be created.
 * @TYPO3\CMS\Extbase\Annotation\Validate("MyVendor\BlogExample\Domain\Validator\CustomUserValidator", param="user")
 */
public function createUserAction($pageName, \MyVendor\ExtbaseExample\Domain\Model\User $user)
{
    // ...
}

Here the following properties are validated: $pageName must be a string. The data type of the @param annotation is validated. For $user all @TYPO3\CMS\Extbase\Annotation\Validate annotations of the model are validated. Also the \MyVendor\BlogExample\Domain\Validator\UserValidator is called if it exists. Beyond that the validator \MyVendor\BlogExample\Domain\Validator\CustomUserValidator is used to validate $user.

In some use cases it is reasonable that incomplete domain objects are given as arguments. That can be the case for multi page forms, because after filling the first page the domain object is not complete. In this case you can use the annotation @TYPO3\CMS\Extbase\Annotation\IgnoreValidation("parameter"). This prevents the processing of the @TYPO3\CMS\Extbase\Annotation\Validate annotations in the domain model and calling the validator class of the domain object.

Case study: Edit an existing object

Now you know all the building blocks you need to edit a blog object with a form. As of now, the edit form should be displayed again in case of a validation error. Two actions are involved at editing the blog: The editAction shows the form with the blog to be edited and the updateAction saves the changes.

Tip

If you want to implement edit forms for the domain objects of your extension you should implement it according to the schema displayed here.

The editAction for the blog looks like this:

public function editAction(\MyVendor\BlogExample\Domain\Model\Blog $blog)
{
    $this->view->assign('blog', $blog);
}

The blog object that we want to edit is passed and given to the view. The Fluid template than looks like this (slightly shortened and reduced to the important):

<f:form name="blog" object="{blog}" action="update">
    <f:form.textfield property="title" />
    <f:form.textarea property="description" />
    <f:form.submit />
</f:form>

Note that the blog object to be edited is bound to the form with object="{blog}". With this you can reference a property of the linked object with help of the property attribute of the form elements.

Also the name of the form (name="blog") is important because it is used as a variable name for the object to be sent. When submitting the form the updateAction is called with the blog object as parameter.

public function updateAction(\MyVendor\BlogExample\Domain\Model\Blog $blog)
{
    $this->blogRepository->update($blog);
}

So the name of the argument is $blog because the form has the name blog. When no validation errors occur, the blog object will be persisted with its changes.

Now have a look what happens when the user inserts erroneous data into the form. In this case an error occurs when validating the $blog arguments. Therefore instead of the updateAction, the errorAction is called. This action routes the request with forward() to the last used action because in case of an error the form should be displayed again. Additionally, an error message is generated and given to the controller. Ergo: In case of a validation error the editAction is displayed again.

As we want to display the erroneous object again it is important that the updateAction and editAction use the same argument names. In our example the argument is called $blog in both cases, so we are on the safe side.

Now we have another problem: The editAction validates all parameters, but our blog object is not valid - we are trapped in an endless loop. Therefore we have to suppress the argument validation for the editAction. For this we need the annotation @TYPO3\CMS\Extbase\Annotation\IgnoreValidation – the comment block of the editAction must be changed like this:

<?php
declare(strict_types = 1);

namespace MyVendor\BlogExample\Controller;

use TYPO3\CMS\Extbase\Annotation as Extbase;
use TYPO3\CMS\Extbase\Mvc\Controller\ActionController;

class BlogController extends ActionController
{
    /**
     * @param \MyVendor\BlogExample\Domain\Model\Blog $blog The blog object
     * @Extbase\IgnoreValidation("blog")
     */
    public function editAction(\MyVendor\BlogExample\Domain\Model\Blog $blog)
    {
        $this->view->assign('blog', $blog);
    }
}

Now the blog object is not validated in the editAction. So also a non valid blog object is displayed correct.

Tip

If Extbase throws the exception TYPO3CMSExtbaseMvcExceptionInfiniteLoopException it signs that the @TYPO3\CMS\Extbase\Annotation\IgnoreValidation annotation is missing.

Fluid automatically adds the CSS class f3-form-error to all erroneous fields - so you can frame them in red for example using CSS. There is also a flashMessages ViewHelper which outputs the error messages of the validation.

Case study: Create an object

In the last section you have seen how to edit a blog object with a form. Now we will show you how to create a new blog object with a form. Also for creating a blog object two actions are involved. The newAction shows a form for creating an object and the createAction finally stores the object.

The only difference to the editing of an object is that the newAction is not always given an argument: when first displaying the form it is logical that there is no object available to be displayed. Therefore the argument must be marked as optional.

Here you will see all that we need. At first the controller code:

<?php
declare(strict_types = 1);

use TYPO3\CMS\Extbase\Annotation as Extbase;
use TYPO3\CMS\Extbase\Mvc\Controller\ActionController;

class BlogController extends ActionController
{
    /**
     * This action shows the 'new' form for the blog.
     *
     * @param \MyVendor\BlogExample\Domain\Model\Blog $newBlog The optional default values
     * @Extbase\IgnoreValidation("newBlog")
     */
    public function newAction(\MyVendor\BlogExample\Domain\Model\Blog $newBlog = NULL)
    {
        $this->view->assign('newBlog', $newBlog);
    }

    /**
     * This action creates the blog and stores it.
     *
     * @param \MyVendor\BlogExample\Domain\Model\Blog $newBlog
     */
    public function createAction(\MyVendor\BlogExample\Domain\Model\Blog $newBlog)
    {
        $this->blogRepository->add($newBlog);
    }
}

The Fluid template for the newAction looks like this (in short form):

<f:flashMessages />
<f:form name="newBlog" object="{newBlog}" action="create">
    <f:form.textfield property="title" />
    <f:form.textarea property="description" />
    <f:form.submit />
</f:form>

What is the summary of what we have done? Again it is important that the newAction and the createAction have the same argument name. This also has to conform with the name of the Fluid template (newBlog in the example). Also the parameter for the newAction must be marked as optional and the validation of the parameter must be suppressed with @TYPO3\CMS\Extbase\Annotation\IgnoreValidation. Finally you can output validation errors in the template using the flashMessages ViewHelper when saving the data.

In figure 9-2 you can find an overview of the behavior of Extbase when displaying, editing respectively creating of domain objects in the frontend.

Figure 9-2: Data flow of the form display and saving. When a validating error occurs it is displayed again.

Mapping arguments

In this section we will describe in detail what happens during a request before the respective action is called, especially when sending a form. Because the HTTP protocol (and PHP) can only transfer arrays and strings, a large array with data is transferred when sending a form. In the action, domain objects are often expected as input parameter, so somehow the array must become an object. That is done by Extbase during the Argument Mappings. It makes it possible that as a user of Extbase you not only work with arrays, but you can change objects in forms or give over a complete object as parameter in links.

Lets have a look at all of this in a concrete example: We pick up the blog example extension and edit a blog object, like you got to know in the last section ("Case study: Edit an existing object"). When you edit a blog you see a form in which you can change the properties of the blog, in our case title and description.

The Fluid form looks like this (shortened to the essential):

<f:form method="post" action="update" name="blog" object="{blog}">
    <f:form.textfield property="title" />
    <f:form.textarea property="description" />
</f:form>

If the form is submitted the data will be sent in the following manner to the server:

tx_blogexample_pi1[blog][__identity] = 5
tx_blogexample_pi1[blog][title] = My title
tx_blogexample_pi1[blog][description] = Description

First of all the data is tagged with a prefix that contains the name of the extension and the plugin (tx_blogexample_pi1). This makes sure that two extensions have no impact on each other. Furthermore all changed properties of the blog object are transferred in an array, in our case title and description. As we want to change a blog object, we also need the identity of the blog object. In order to do this, Fluid automatically adds the __identity property for the blog object and fills it with the UID of the blog.

Now on the server side a blog object must be created out of this information. This is the job of the property mapper. Its operation method is shown in figure 9-3.

For every argument it must be decided first whether a new object has to be created or if the work is based on an existing object. This will be decided based on the identity property __identity. If this is not in the input data a new object is created. Otherwise the framework knows the object identity and can continue working with it.

Tip

When you take a look at what is transferred to the server by the new action of the blog example, you will find that no identity properties are transferred - in this case a new object is created as intended.

In the blog example from above the __identity property is available, therefore the object with the corresponding UID is fetched from the repository and used for further modification.

When no properties should be changed the object is given as argument to the action. So that is always persistent, that is changes to this object are saved automatically. <remark>!!!Sentence not clear</remark>

Figure 9-3: The internal control flow of the property mapper.

In our case not only is the __identity property sent, but also a new title and description for our blog. For safety reasons a copy of the persistent object is applied. The properties of the copy are changed as given in the request, in our case title and description are set new. The generated copy is yet a transient object (see section "live cycle of objects" in chapter 2), that is changes on the object are not automatically persisted. The changed copy is given to the action as argument.

Now we have to explicitly tell our controller that we want to replace the existing persistent blog object with our modified blog object. For this, the repository provides the method update():

$this->blogRepository->update($blog);

With this the changed object will be made into the persistent object: The changes are now permanently stored.

Copies of objects

Why a copy of an object is created when it is to be changed? Lets assume that the persistent object would be directly changed. In this case an empty controller would be updating persistent objects:

public function updateAction(\MyVendor\BlogExample\Domain\Model\Blog $blog)
{
    // object will be automatically persisted
}

This is not transparent and difficult to understand. Besides that, this procedure introduces a big safety issue: When the original object is changed it would be impossible to cancel the persisting of the changes. For this reason a copy of the object is returned for changed objects, so the developer of the extension has to decide explicit whether or not the changes are to be made persistent.

We want to assume a refinement of the argument mapping: When a link to an action is generated and the link contains an object as parameter the identity of the object is transferred automatically. In the following example the UID is transferred instead of the blog object:

<f:link.action action='show' arguments='{blog: blog}'>Show Blog</f:link.action>

The generated URL contains the identity of the blog object: tx_blogexample_pi1[blog]=47. That is a short form of tx_blogexample_pi1[blog][__Identity]=47. Therefore the property mapper gets the blog object with the identity 47 from the repository and returns it directly without copying before.

Now that you know about argument mapping in greater detail an can begin to use it in your own projects.

After you have learned how you can make sure any invariants of domain objects, the focus will be directed to the secure programming of the complete extension.