µWeb

h1. Request

{{>toc}}

The @Request@ object is an abstraction of the incoming HTTP request. This allows one simple interface that is independent of the underlying server that µWeb runs on (either [[Standalone]] using BaseHTTPServer, or [[Apache]] mode on @mod_python@).

From PageMaker methods, the request object is accessible as the @self.req@ member. The request object contains all the information about the incoming request: query arguments, post data, cookies and environment data. It is also the object where you define cookies that need to be provided to the client.

h1. Query arguments

All query arguments provided by the client are present on the request object. They are also accessible directly on the [[PageMaker]] object. The following code demonstrates both ways to access a query argument:

<pre><code class="html">

...

<form>

  <label for="name">Name: </label><input id="name" name="name" />

  <input type="submit" value="Tell us your name" />

</form>

...

</code></pre>

<pre><code class="python">

def NameFromQuery(self):

  # Retrieves the 'name' argument from the request object:

  name = self.req.vars['get'].getfirst('name')

  # Retrieves the 'name' argument directly from the PageMaker instance (linked to the request):

  name = self.get.getfirst('name')

  return name

</code></pre>

Using the @getfirst@ method, you get a single string returned from the query argument mapping, or a @None@ if no such value exists. Much like a dictionary's @get@ method, you can provide a second argument to the method, and have that returned instead as the default. 

Now, HTTP allows the client to provide the same query argument multiple times. Using @getfirst@ you would only get the very first defined argument. So a request that looks like @http://example.org/group?name=Bob&name=Mark&name=Jenny@ would only return 'Bob' in the previous example. To get all their names printed, you can use the following:

<pre><code class="html">

...

<form action="/group">

  <h2>Names in this group</h2>

  <!-- These would likely be generated with Javascript, but written here for demonstrative purposes -->

  <label for="name_1">Name: </label><input id="name_1" name="name" />

  <label for="name_2">Name: </label><input id="name_2" name="name" />

  <label for="name_3">Name: </label><input id="name_3" name="name" />

  <input type="submit" value="Send these names" />

</form>

...

</code></pre>

<pre><code class="python">

def MemberNames(self):

  names = self.get.getlist('name')

  return ', '.join(names)

</code></pre>

This returns a neat comma-separated string with all the provided names. The @getlist@ method does not take a default, but will instead return an empty list when there are no values for the requested argument name.

h1. Post data

Submitted form data is available on the request object as well. The interface is similar to that of the query arguments, and the @FieldStorage@ class already present in the @cgi@ module. If we take our initial example form handler, but now receive the data through HTTP POST, the code would look like this:

<pre><code class="html">

...

<form method="post">

  <label for="name">Name: </label><input id="name" name="name" />

  <input type="submit" value="Tell us your name" />

</form>

...

</code></pre>

<pre><code class="python">

def NameFromPost(self):

  # Retrieves the 'name' value from the request object:

  name = self.req.vars['post'].getfirst('name')

  # Retrieves the 'name' value directly from the PageMaker instance (linked to the request):

  name = self.post.getfirst('name')

  return name

</code></pre>

Like with the query arguments, @getfirst@ accepts a second argument that provides a default other than @None@.

Multiple values are again possible in the FieldStorage, and these work similar to how they do in query arguments:

<pre><code class="html">

...

<form action="/group" method="post">

  <h2>Names in this group</h2>

  <!-- These would likely be generated with Javascript, but written here for demonstrative purposes -->

  <label for="name_1">Name: </label><input id="name_1" name="name" />

  <label for="name_2">Name: </label><input id="name_2" name="name" />

  <label for="name_3">Name: </label><input id="name_3" name="name" />

  <input type="submit" value="Send these names" />

</form>

...

</code></pre>

<pre><code class="python">

def MemberNames(self):

  names = self.post.getlist('name')

  return ', '.join(names)

</code></pre>

h2. Uploading files

Processing an uploaded file is done using the the same @FieldStorage@ system as the rest of the POST data, and roughly looks like the following. When performing file uploads, be sure to define the @enctype@ of your form, or the uploaded file will have no contents.

<pre><code class="html">

...

<form method="post" enctype="multipart/form-data">

  <label for="avatar">Avatar: </label><input id="avatar" name="avatar" type="file" />

  <input type="submit" value="submit!" />

</form>

...

</code></pre>

<pre><code class="python">

def UpdateAvatar(self):

  # Retrieve the currently logged-in user

  user = self.GetCurrentUser()

  # This gets the name of the file that was uploaded

  avatar_name = self.post['avatar'].filename

  # This retrieves the content of the uploaded file, 

  avatar_data = self.post['avatar'].value

  self.SaveAvatar(user, avatar_data)

  return 'Your avatar has been replaced by %r' % avatar_name

</code></pre>

h2. Structured data using POST

One of the things that has been extended on the basic @FieldStorage@ in µWeb is the way it treats square backets ( [ and ] ) in POST data. A form field with the name @person[name]@ will result in a dictionary @person@ being created in the resulting @FieldStorage@:

<pre><code class="html">

...

<form method="post">

  <label for="name">Name: </label><input id="name" name="person[name]" />

  <label for="age">Age: </label><input id="age" name="person[age]" />

  <label for="job">Job: </label><input id="job" name="person[job]" />

  <input type="submit" value="Update your profile" />

</form>

...

</code></pre>

<pre><code class="python">

def PersonalData(self):

  person = self.post.getfirst('person')

  return uweb.Response(json.dumps(person), content_type="application/json")

</code></pre>

In the above code here, the @person@ variable is a dictionary retrieved from the POST data, which is then presented to the client in JSON, by using a custom [[Response|repsonse]].

Note that the 'numeric' age value is a string. This is of course because everything submitted in forms is in the form of a string. Conversion to appropriate types will have to be handled by the [[PageMaker]]. The @person@ dictionary itself looks like this:

<pre><code class="python">

{'age': '28', 'job': 'Engineer', 'name': 'Elmer'}

</code></pre>

*N.B.:* When using structured form data, you still need to use the @getfirst@ method, because there might me separate (non-dictionary) values for the form name. There will never be more than one dictionary in the form values; if a single key is set more than once, the last-set value will be the one present in the dictionary.

h1. Cookies

self.cookies contains the cookies send by the browser, as the interface to create them from the server.

h3. Retrieving a cookie

You can fetch the content of cookie by accessig the self.cookie dict with the name of the desired cookie as its key.

The returned cookie object has a value member containing the actual value of the requested cookie.

<pre>

<code class="python">

self.cookies['sample'].value

</code>

</pre>

h1. Environment

The env variable is a dictionary containing the following items;

* CONTENT_TYPE

* CONTENT_LENGTH

* HTTP_COOKIE

* HTTP_HOST

* HTTP_REFERER

* HTTP_USER_AGENT

* PATH_INFO

* QUERY_STRING

* REMOTE_ADDR

* REQUEST_METHOD

* UWEB_MODE 'STANDALONE' / 'MOD_PYTHON'

h2. Extended environment

If more detail is required about the environment, you can issue a call to the self.req.ExtendedEnvironment() method, which will inject more details into the env var. This is a much slower operation than the normal env call, so that's why its tucked away in a separate method.

* AUTH_TYPE

* CONNECTION_ID

* DOCUMENT_ROOT

* RAW_REQUEST

* REMOTE_HOST

* REMOTE_USER

* SERVER_NAME

* SERVER_PORT

* SERVER_LOCAL_NAME

* SERVER_LOCAL_IP

* SERVER_PROTOCOL

And in case of a @mod_python@ setup you will also get:

* MODPYTHON_HANDLER

* MODPYTHON_INTERPRETER

* MODPYTHON_PHASE

h1. Setting cookies