Preview does not work with non-standard documents

[danrot]

The scenario described in http://stackoverflow.com/questions/34120232/sulu-extend-pagedocument?noredirect=1#comment56338102_34120232 doesn't work as intended, as the error in this thread explains.

Main point is when creating an own document class and using it with this configuration in app/config/config.yml:

sulu_document_manager:
    mapping:
        page:
            class: Client\Bundle\WebsiteBundle\Document\PageDocument
            phpcr_type: sulu:page

The preview does not work, it just shows the following exception:

After a fast research I could track that down to the deserialization part of the preview. When the class is serialized the document is of the right type (Client\Bundle\WebsiteBundle\Document\PageDocument), but after deserialization the type is again Sulu\Bundle\ContentBundle\Document\PageDocument.

[wachterjohannes]

i have found the exact line of error: https://github.com/sulu-io/sulu/blob/develop/src/Sulu/Component/Content/Compat/Serializer/PageBridgeHandler.php#L94

here we should also store the name of class in the serialized content and use it here. i will create a pr to fix this issue