How to make JMS Serializer throw an exception on deserializing JSON instead of coercing types?

Question

I'm trying to write a REST API which consumes a JSON from a PUT request in Symfony2. Deserializing the JSON to an entity sort of works – but the JMS Serializer seems to coerce types from the JSON instead of throwing an exception if the type of a property in the JSON does not match the entity’s corresponding property.

For example …

{ "id" : "123" }

… will result in …

int(123)

… if the property id is defined as an integer in the entity.

But I would like JMS Serializer to throw an exception instead. Does anyone know how to achieve this?

Update 2016-02-27

One problem with JMS Serializer’s type handling I found is this:

{ "id" : "n123" }

will result in …

int(0)

which is totally undesired.

Can someone please point me into the right direction?

Answer 1

After getting help over at Github I want to share an answer on my own question.

The key to a solution is using a custom handler which implements the JMS\Serializer\Handler\SubscribingHandlerInterface (e.g. a StrictIntegerHandler).

<?php
namespace MyBundle\Serializer;

use JMS\Serializer\Context;
use JMS\Serializer\GraphNavigator;
use JMS\Serializer\Handler\SubscribingHandlerInterface;
use JMS\Serializer\JsonDeserializationVisitor;
use JMS\Serializer\JsonSerializationVisitor;
use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;

class StrictIntegerHandler implements SubscribingHandlerInterface
{
    public static function getSubscribingMethods()
    {
        return [
            [
                'direction' => GraphNavigator::DIRECTION_DESERIALIZATION,
                'format' => 'json',
                'type' => 'strict_integer',
                'method' => 'deserializeStrictIntegerFromJSON',
            ],
            [
                'direction' => GraphNavigator::DIRECTION_SERIALIZATION,
                'format' => 'json',
                'type' => 'strict_integer',
                'method' => 'serializeStrictIntegerToJSON',
            ],
        ];
    }

    public function deserializeStrictIntegerFromJSON(JsonDeserializationVisitor $visitor, $data, array $type)
    {
        return $data;
    }

    public function serializeStrictIntegerToJSON(JsonSerializationVisitor $visitor, $data, array $type, Context $context)
    {
        return $visitor->visitInteger($data, $type, $context);
    }
}

You will then need to define the serializer as a service:

services:
    mybundle.serializer.strictinteger:
        class: MyBundle\Serializer\StrictIntegerHandler
        tags:
            - { name: jms_serializer.subscribing_handler }

Then you will be able to use the type strict_integer:

MyBundle\Entity\MyEntity:
    exclusion_policy: ALL
    properties:
        id:
            expose: true
            type: strict_integer

Deserializing in the controller then works as usual.

Bonus: Using a type validator now finally makes sense:

MyBundle\Entity\MyEntity:
    properties:
        id:
            - Type:
                type: integer
                message: id {{ value }} is not an integer.

I hope this helps those with the same problem.