---
title: "Template per il backend personalizzato"
version: 3.2
locale: it
source: https://docs.djangoproject.com/it/3.2/howto/custom-template-backend/
canonical: https://djangodocs.dev/it/3.2/howto/custom-template-backend/
---
# Template per il backend personalizzato

## Backend personalizzati

Here’s how to implement a custom template backend in order to use another
template system. A template backend is a class that inherits
`django.template.backends.base.BaseEngine`. It must implement
`get_template()` and optionally `from_string()`. Here’s an example for a
fictional `foobar` template library:

```
from django.template import TemplateDoesNotExist, TemplateSyntaxError
from django.template.backends.base import BaseEngine
from django.template.backends.utils import csrf_input_lazy, csrf_token_lazy

import foobar

class FooBar(BaseEngine):

    # Name of the subdirectory containing the templates for this engine
    # inside an installed application.
    app_dirname = 'foobar'

    def __init__(self, params):
        params = params.copy()
        options = params.pop('OPTIONS').copy()
        super().__init__(params)

        self.engine = foobar.Engine(**options)

    def from_string(self, template_code):
        try:
            return Template(self.engine.from_string(template_code))
        except foobar.TemplateCompilationFailed as exc:
            raise TemplateSyntaxError(exc.args)

    def get_template(self, template_name):
        try:
            return Template(self.engine.get_template(template_name))
        except foobar.TemplateNotFound as exc:
            raise TemplateDoesNotExist(exc.args, backend=self)
        except foobar.TemplateCompilationFailed as exc:
            raise TemplateSyntaxError(exc.args)

class Template:

    def __init__(self, template):
        self.template = template

    def render(self, context=None, request=None):
        if context is None:
            context = {}
        if request is not None:
            context['request'] = request
            context['csrf_input'] = csrf_input_lazy(request)
            context['csrf_token'] = csrf_token_lazy(request)
        return self.template.render(context)
```

Vedi [DEP 182](https://github.com/django/deps/blob/main/final/0182-multiple-template-engines.rst) per maggiori informazioni.

## Debug integration for custom engines

The Django debug page has hooks to provide detailed information when a template
error arises. Custom template engines can use these hooks to enhance the
traceback information that appears to users. The following hooks are available:

### Template postmortem

The postmortem appears when [`TemplateDoesNotExist`](/it/3.2/topics/templates/#django.template.TemplateDoesNotExist) is
raised. It lists the template engines and loaders that were used when trying to
find a given template. For example, if two Django engines are configured, the
postmortem will appear like:

![](howto/_images/postmortem.png)

Custom engines can populate the postmortem by passing the `backend` and
`tried` arguments when raising [`TemplateDoesNotExist`](/it/3.2/topics/templates/#django.template.TemplateDoesNotExist).
Backends that use the postmortem [should specify an origin](#template-origin-api) on the template object.

### Contextual line information

Se viene generato un errore durante il parsing o il rendering del template, Django è in grado di mostrare la riga in cui è presente l’errore. Ad esempio:

![](howto/_images/template-lines.png)

Custom engines can populate this information by setting a `template_debug`
attribute on exceptions raised during parsing and rendering. This attribute is
a [`dict`](https://docs.python.org/3/library/stdtypes.html#dict) with the following values:

- `'name'`: Il nome del template in cui è avvenuta l’eccezione.
- `'message'`: Il messaggio dell’eccezione
- `'source_lines'`: Le righe prima, dopo e che includono la riga dove è avvenuta l’eccezione. Questo è per il contesto, quindi non dovrebbe contenere più di 20 righe o giù di lì.
- `'line'`: Il numero di riga in cui è avvenuta l’eccezione.
- `'before'`: Il contenuto della riga dell’errore prima del token che ha generato l’errore.
- `'during'`: Il token che ha generato l’errore.
- `'after'`: Il contenuto della riga dell’errore dopo il token che ha generato l’errore.
- `'total'`: Il numero di righe in `source_lines`.
- `'top'`: Il numero di riga dove inizia `source_lines`.
- `'bottom'`: Il numero di riga dove termina `source_lines`.

Dato il template di errore qui sopra, `template_debug` sarà simile a:

```
{
    'name': '/path/to/template.html',
    'message': "Invalid block tag: 'syntax'",
    'source_lines': [
        (1, 'some\n'),
        (2, 'lines\n'),
        (3, 'before\n'),
        (4, 'Hello {% syntax error %} {{ world }}\n'),
        (5, 'some\n'),
        (6, 'lines\n'),
        (7, 'after\n'),
        (8, ''),
    ],
    'line': 4,
    'before': 'Hello ',
    'during': '{% syntax error %}',
    'after': ' {{ world }}\n',
    'total': 9,
    'bottom': 9,
    'top': 1,
}
```

### Origin API and 3rd-party integration

Django templates have an [`Origin`](/it/3.2/ref/templates/api/#django.template.base.Origin) object available
through the `template.origin` attribute. This enables debug information to be
displayed in the [template postmortem](#template-postmortem), as well as
in 3rd-party libraries, like the [Django Debug Toolbar](https://github.com/jazzband/django-debug-toolbar/).

Custom engines can provide their own `template.origin` information by
creating an object that specifies the following attributes:

- `'name'`: The full path to the template.
- `'template_name'`: The relative path to the template as passed into the
  template loading methods.
- `'loader_name'`: An optional string identifying the function or class used
  to load the template, e.g. `django.template.loaders.filesystem.Loader`.