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34 lines
1.4 KiB
34 lines
1.4 KiB
15 years ago
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Step 4: Request Database Connections
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------------------------------------
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Now we know how we can open database connections and use them for scripts,
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but how can we elegantly do that for requests? We will need the database
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connection in all our functions so it makes sense to initialize them
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before each request and shut them down afterwards.
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Flask allows us to do that with the :meth:`~flask.Flask.before_request` and
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:meth:`~flask.Flask.after_request` decorators::
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@app.before_request
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def before_request():
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g.db = connect_db()
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@app.after_request
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def after_request(response):
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g.db.close()
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return response
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Functions marked with :meth:`~flask.Flask.before_request` are called before
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a request and passed no arguments, functions marked with
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:meth:`~flask.Flask.after_request` are called after a request and
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passed the response that will be sent to the client. They have to return
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that response object or a different one. In this case we just return it
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unchanged.
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We store our current database connection on the special :data:`~flask.g`
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object that flask provides for us. This object stores information for one
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request only and is available from within each function. Never store such
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things on other objects because this would not work with threaded
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environments. That special :data:`~flask.g` object does some magic behind
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the scenes to ensure it does the right thing.
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