~ntt-pf-lab/nova/monkey_patch_notification

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<title>Twisted Documentation: Session Basics</title>

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<h1 class="title">Session Basics</h1>

Sessions are the most complicated topic covered in this series of examples,

and because of that it is going to take a few examples to cover all of the

different aspects. This first example demonstrates the very basics of the

Twisted Web session API: how to get the session object for the current request

and how to prematurely expire a session.

Before diving into the APIs, let's look at the big picture of sessions in

Twisted Web. Sessions are represented by instances of <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.server.Session.html" title="twisted.web.server.Session">Session</a></code>. The <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.server.Site.html" title="twisted.web.server.Site">Site</a></code> creates a new instance of

<code>Session</code> the first time an application asks for it for a particular

session. <code>Session</code> instances are kept on the <code>Site</code>

instance until they expire (due to inactivity or because they are explicitly

expired). Each time after the first that a particular session's

<code>Session</code> object is requested, it is retrieved from

the <code>Site</code>.

With the conceptual underpinnings of the upcoming API in place, here comes

the example. This will be a very simple <a href="rpy-scripts.html" shape="rect">rpy

script</a> which tells a user what its unique session identifier is and lets it

prematurely expire the session.

First, we'll import <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.resource.Resource.html" title="twisted.web.resource.Resource">Resource</a></code> so we can define a couple of

subclasses of it:

<pre class="python">1

from twisted.web.resource import Resource

</pre>

Next we'll define the resource which tells the client what its session

identifier is. This is done easily by first getting the session object

using <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.server.Request.getSession.html" title="twisted.web.server.Request.getSession">Request.getSession</a></code> and

then getting the session object's uid attribute:

<pre class="python">1

class ShowSession(Resource):

def render_GET(self, request):

return 'Your session id is: ' + request.getSession().uid

</pre>

To let the client expire its own session before it times out, we'll define

another resource which expires whatever session it is requested with. This is

done using the <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.server.Session.expire.html" title="twisted.web.server.Session.expire">Session.expire</a></code>

method:

<pre class="python">1

class ExpireSession(Resource):

def render_GET(self, request):

request.getSession().expire()

return 'Your session has been expired.'

</pre>

Finally, to make the example an rpy script, we'll make an instance of

<code>ShowSession</code> and give it an instance of <code>ExpireSession</code>

as a child using <code class="API"><a href="http://twistedmatrix.com/documents/10.0.0/api/twisted.web.resource.Resource.putChild.html" title="twisted.web.resource.Resource.putChild">Resource.putChild</a></code>:

<pre class="python">1

resource = ShowSession()

resource.putChild("expire", ExpireSession())

</pre>

And that is the complete example. You can fire this up and load the top

page. You'll see a (rather opaque) session identifier that remains the same

across reloads (at least until you flush the <code>TWISTED_SESSION</code> cookie

from your browser or enough time passes). You can then visit

the <code>expire</code> child and go back to the top page and see that you have

a new session.

Here's the complete source for the example:

<pre class="python"> 1

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class ShowSession(Resource):

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def render_GET(self, request):

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class ExpireSession(Resource):

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def render_GET(self, request):

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request.getSession().expire()

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return 'Your session has been expired.'

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resource = ShowSession()

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resource.putChild("expire", ExpireSession())

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</pre>

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<a href="../index.html">Index</a>

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Version: 10.0.0

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