# User Application

Tryton provides a way to connect URL rules to an callable endpoint using the decorator method `route` of the `trytond.application.app` instance. This allows you to define a custom API based on HTTP that can be used to create a specific user application.

The decorator takes as first parameter a string which follow the Rule Format of Werkzeug and as second parameter sequence of HTTP methods.

Example:

    from trytond.application import app

    @app.route('/hello', methods=['GET'])
    def hello(request):
        return 'Hello world'

The following converter is added by Tryton:

> - `base64`: This converter accepts any Base64 string and transforms it into its corresponding bytes value.

Tryton also provides some wrappers in `trytond.protocols.wrappers` to ease the creation of such route.

> - `set_max_request_size(size)`: change the default limit of the request to the size in bytes.

> - `allow_null_origin`: allow requests which have their `Origin` set to `null`.

> - `with_pool`: which takes the first parameter as database name and replace it by the corresponding instance of the Pool.

> - `with_transaction([readonly])`: which starts a `Transaction` using the Pool from `with_pool`. If `readonly` is not set, the transaction will not be readonly for `POST`, `PUT`, `DELETE` and `PATCH` methods and readonly for all others.

> - `user_application(name[, json])`: which set the `Transaction.user` from the `Authorization` header using the type `bearer` and a valid key for the named user application.

## User Application Key

Tryton also provides a easy way to manage access to user application using keys per named application. A key is created with a `POST` request on the `URL` `/<database_name>/user/application/` which returns the key. The request must contain as data a json object with the keys:

> - `user`: the user login

> - `application`: the name of the application

After the creation, the key must be validated by the user from the preferences of a Tryton client.

A key can be deleted with a `DELETE` request on the same `URL`. The request must contain as data a json object with the keys:

> - `user`: the user login

> - `key`: the key to delete

> - `application`: the name of the application of the key