Customizing the API

Content serialization

Dexterity fields

The API automatically converts all field values to JSON compatible data, whenever possible. However, you might use fields which store data that cannot be automatically converted, or you might want to customize the representation of certain fields.

For extending or changing the serializing of certain dexterity fields you need to register an IFieldSerializer-adapter.


from plone.customfield.interfaces import ICustomField
from plone.dexterity.interfaces import IDexterityContent
from plone.restapi.interfaces import IFieldSerializer
from plone.restapi.serializer.converters import json_compatible
from plone.restapi.serializer.dxfields import DefaultFieldSerializer
from zope.component import adapter
from zope.interface import Interface
from zope.interface import implementer

@adapter(ICustomField, IDexterityContent, Interface)
class CustomFieldSerializer(DefaultFieldSerializer):

    def __call__(self):
        value = self.get_value()
        if value is not None:
            # Do custom serializing here, e.g.:
            value = value.output()

        return json_compatible(value)

Register the adapter in ZCML:

<configure xmlns="">

    <adapter factory=".serializer.CustomFieldSerializer" />


The json_compatible function recursively converts the value to JSON compatible data, when possible. When a value cannot be converted, a TypeError is raised. It is recommended to pass all values through json_compatible in order to validate and convert them.

For customizing a specific field instance, a named IFieldSerializer adapter can be registered. The name may either be the full dottedname of the field ( or the shortname of the field (exclude_from_nav).