============= Using Sandman ============= The Simplest Application ------------------------ Here's what's required to create a RESTful API service from an existing database using ``sandman`` :: $ sandmanctl sqlite:////tmp/my_database.db *That's it.* ``sandman`` will then do the following: * Connect to your database and introspect it's contents * Create and launch a RESTful API service * Create an HTML admin interface * *Open your browser to the admin interface* That's right. Given a legacy database, ``sandman`` not only gives you a REST API, it gives you a beautiful admin page and *opens your browser to the admin page*. It truly does everything for you. Supported Databases ------------------- ``sandman`` , by default, supports connections to the same set of databases as SQLAlchemy (http://www.sqlalchemy.org). As of this writing, that includes: * MySQL (MariaDB) * PostgreSQL * SQLite * Oracle * Microsoft SQL Server * Firebird * Drizzle * Sybase * IBM DB2 * SAP Sybase SQL Anywhere * MonetDB Beyond `sandmanctl` ------------------- ``sandmanctl`` is really just a simple wrapper around the following:: from ``sandman`` import app app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///chinook' from sandman.model import activate activate(browser=True) app.run() **Notice you don't even need to tell ``sandman`` what tables your database contains.** Just point ``sandman`` at your database and let it do all the heavy lifting. If you put the code above into a file named ``runserver.py``, You can start this new service and make a request. While we're at it, lets make use of ``sandman``'s awesome filtering capability by specifying a filter term:: $ python runserver.py & * Running on http://127.0.0.1:5000/ > curl GET "http://localhost:5000/artists?Name=AC/DC" you should see the following:: { "resources": [ { "ArtistId": 1, "Name": "AC/DC", "links": [ { "rel": "self", "uri": "/artists/1" } ] } ] } If you were to leave off the filtering term, you would get **all** results from the ``Artist`` table. You can also *paginate* these results by specifying ``?page=2`` or something similar. The number of results returned per page is controlled by the config value ``RESULTS_PER_PAGE``, which defaults to 20. A Quick Guide to REST APIs ~~~~~~~~~~~~~~~~~~~~~~~~~~ Before we get into more complicated examples, we should discuss some REST API basics. The most important concept is that of a *resource*. Resources are sources of information, and the API is an interface to this information. That is, resources are the actual "objects" manipulated by the API. In ``sandman``, each row in a database table is considered a resource. Groups of resources are called *collections*. In ``sandman``, each table in your database is a collection. Collections can be queried and added to using the appropriate *HTTP method*. ``sandman`` supports the following HTTP methods:: * GET * POST * PUT * DELETE * PATCH (Support for the ``HEAD`` and ``OPTIONS`` methods is underway.) =============== Creating Models =============== A ``Model`` represents a table in your database. You control which tables to expose in the API through the creation of classes which inherit from :class:`sandman.model.models.Model`. If you create a ``Model``, the only attribute you must define in your class is the ``__tablename__`` attribute. ``sandman`` uses this to map your class to the corresponding database table. From there, ``sandman`` is able to divine all other properties of your tables. Specifically, ``sandman`` creates the following: - an ``__endpoint__`` attribute that controls resource URIs for the class - a ``__methods__`` attribute that determines the allowed HTTP methods for the class - ``as_dict`` and ``from_dict`` methods that only operate on class attributes that correspond to database columns - an ``update`` method that updates only the values specified (as opposed to ``from_dict``, which replaces all of the object's values with those passed in the dictionary parameter - ``links``, ``primary_key``, and ``resource_uri`` methods that provide access to various attributes of the object derived from the underlying database model Creating a ``models.py`` file allows you to get *even more* out of ``sandman``. In the file, create a class that derives from ``sandman.models.Model`` for each table you want to turn into a RESTful resource. Here's a simple example using the Chinook test database (widely available online):: from sandman.model import register, activate, Model class Artist(Model): __tablename__ = 'Artist' class Album(Model): __tablename__ = 'Album' class Playlist(Model): __tablename__ = 'Playlist' class Genre(Model): __tablename__ = 'Genre' # register can be called with an iterable or a single class register((Artist, Album, Playlist)) register(Genre) # activate must be called *after* register activate(browser=False) Hooking up Models ----------------- The ``__tablename__`` attribute is used to tell ``sandman`` which database table this class is modeling. It has *no default* and is *required* for all classes. Providing a custom endpoint --------------------------- In the code above, we created four :class:`sandman.model.models.Model` classes that correspond to tables in our database. If we wanted to change the HTTP endpoint for one of the models (the default endpoint is simply the class's name pluralized in lowercase), we would do so by setting the ``__endpoint__`` attribute in the definition of the class:: class Genre(Model): __tablename__ = 'Genre' __endpoint__ = 'styles' Now we would point our browser (or ``curl``) to ``localhost:5000/styles`` to retrieve the resources in the ``Genre`` table. Restricting allowable methods on a resource ------------------------------------------- Many times, we'd like to specify that certain actions can only be carried out against certain types of resources. If we wanted to prevent API users from deleting any ``Genre`` resources, for example, we could specify this implicitly by defining the ``__methods__`` attribute and leaving out the ``DELETE`` method, like so:: class Genre(Model): __tablename__ = 'Genre' __endpoint__ = 'styles' __methods__ = ('GET', 'POST', 'PATCH', 'PUT') For each call into the API, the HTTP method used is validated against the acceptable methods for that resource. Performing custom validation on a resource ------------------------------------------ Specifying which HTTP methods are acceptable gives rather coarse control over how a user of the API can interact with our resources. For more granular control, custom a validation function can be specified. To do so, simply define a static method named ``validate_``, where ```` is the HTTP method the validation function should validate. To validate the ``POST`` method on ``Genres``, we would define the method ``validate_POST``, like so:: class Genre(Model): __tablename__ = 'Genre' __endpoint__ = 'styles' __methods__ = ('GET', 'POST', 'PATCH', 'PUT') @staticmethod def validate_POST(self, resource=None): if isinstance(resource, list): return True # No classical music! return resource and resource.Name != 'classical' The ``validate_POST`` method is called *after* the would-be resource is created, trading a bit of performance for a simpler interface. Instead of needing to inspect the incoming HTTP request directly, you can make validation decisions based on the resource itself. Note that the ``resource`` parameter can be either a single resource or a collection of resources, so it's usually necessary to check which type you're dealing with. This will likely change in a future version of sandman. Configuring a model's behavior in the admin interface ----------------------------------------------------- ``sandman`` uses `Flask-Admin` to construct the admin interface. While the default settings for individual models are usually sufficient, you can make changes to the admin interface for a model by setting the `__view__` attribute to a class that derives from `flask.ext.admin.contrib.sqla.ModelView`. The Flask-Admin's documentation should be consulted for the full list of attributes that can be configured. Below, we create a model and, additionally, tell ``sandman`` that we want the table's primary key to be displayed in the admin interface (by default, a table's primary keys aren't shown):: from flask.ext.admin.contrib.sqla import ModelView class ModelViewShowPK(ModelView): column_display_pk = True class Artist(Model): __tablename__ = 'Artist' __view__ = ModelViewShowPK **Custom `__view__` classes are a powerful way to customize the admin interface.** Properties exist to control which columns are sortable or searchable, as well as as what fields are editable in the built-in editing view. If you find your admin page isn't working exactly as you'd like, the chances are good you can add your desired functionality through a custom `__view__` class. =============== Model Endpoints =============== If you were to create a ``Model`` class named ``Resource``, the following endpoints would be created: * ``resources/`` * ``GET``: retrieve all resources (i.e. the *collection*) * ``POST``: create a new resource * ``resources/`` * ``GET``: retrieve a specific resource * ``PATCH``: update an existing resource * ``PUT``: create or update a resource with the given ID * ``DELETE``: delete a specific resource * ``resources/meta`` * ``GET``: retrieve a description of a resource's structure The root endpoint ----------------- For each project, a "root" endpoint (``/``) is created that gives clients the information required to interact with your API. The endpoint for each resource is listed, along with the ``/meta`` endpoint describing a resource's structure. The root endpoint is available as both JSON and HTML. The same information is returned by each version. The ``/meta`` endpoint ---------------------- A ``/meta`` endpoint, which lists the models attributes (i.e. the database columns) and their type. This can be used to create client code that is decoupled from the structure of your database. A ``/meta`` endpoint is automatically generated for every ``Model`` you register. This is available both as JSON and HTML. ======================= Automatic Introspection ======================= Of course, you don't actually need to tell ``sandman`` about your tables; it's perfectly capable of introspecting all of them. To use introspection to make *all* of your database tables available via the admin and REST API, simply remove all model code and call `activate()` without ever registering a model. To stop a browser window from automatically popping up on sandman initialization, call `activate()` with `browser=False`. ========================================= Running ``sandman`` alongside another app ========================================= If you have an existing WSGI application you'd like to run in the same interpreter as ``sandman``, follow the instructions described here_. Essentially, you need to import both applications in your main file and use Flask's ``DispatcherMiddleware`` to give a unique route to each app. In the following example, ``sandman``-related endpoints can be accessed by adding the ``/sandman`` prefix to ``sandman``'s normally generated URIs:: from my_application import app as my_app from sandman import app as sandman_app from werkzeug.wsgi import DispatcherMiddleware application = DispatcherMiddleware(my_app, { '/sandman': sandman_app, }) This allows both apps to coexist; ``my_app`` will be rooted at ``/`` and ``sandman`` at ``/sandman``. Using existing declarative models --------------------------------- If you have a Flask/SQLAlchemy application that already has a number of existing declarative models, you can register these with ``sandman`` as if they were auto-generated classes. Simply add your existing classes in the call to :func:`sandman.model.register` .. _here: http://flask.pocoo.org/docs/patterns/appdispatch/#app-dispatch