Submitting Form
Data to the Server in WML
In
the earlier sections of this WML tutorial, we have mentioned about
how to use input fields and selection lists to create forms and
obtain data from a user. In many situations, you need to submit the
form data to the server for further processing. To submit data to the
server in WML, you need the <go></go> and <postfield/>
tags. The <postfield/> tag should be enclosed in the <go></go>
tag pair. Let's first have a look at the following WML example before
we go into the details:
(sendDataEg1.wml)
<?xml
version="1.0"?>
<!DOCTYPE wml PUBLIC
"-//WAPFORUM//DTD WML 1.3//EN"
"http://www.wapforum.org/DTD/wml13.dtd">
<wml>
<card
id="card1" title="WML Form">
<onevent
type="onenterforward">
<refresh>
<setvar
name="my_temp_id"
value="123456"/>
</refresh>
</onevent>
<p>
Hello,
welcome to our WML tutorial.<br/>
What's
your name?<br/>
<input
name="myName"/><br/>
Are you a boy or
a girl?<br/>
<select
name="myGender">
<option value="Boy">I
am a boy</option>
<option value="Girl">I
am a girl</option>
</select><br/>
Which
part of our WML tutorial do you like?<br/>
<select
name="favorite_tutorial_part"
multiple="true">
<option value="Part
1">Part 1</option>
<option value="Part
2">Part 2</option>
<option value="Part
3">Part 3</option>
<option value="Part
4">Part
4</option>
</select><br/><br/>
<anchor>
<go
method="get" href="processing.asp">
<postfield
name="name" value="$(myName)"/>
<postfield
name="gender" value="$(myGender)"/>
<postfield
name="tutorial_part"
value="$(favorite_tutorial_part)"/>
<postfield
name="temp_id"
value="$(my_temp_id)"/>
</go>
Submit
Data
</anchor>
</p>
</card>
</wml>
The
following screenshots show what you will see if you open the above
WML document in some mobile phone browsers:
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Sony
Ericsson T610
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Sony
Ericsson T68i
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Nokia
Mobile Browser 4.0
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In
the above WML example, one input field and two selection lists are
created to obtain user data. If a user clicks the "Submit Data"
anchor link, the form data will be submitted to the server. Unlike
HTML, WML does not support the creation of submit buttons.
The
method attribute of the <go> tag specifies which HTTP
method should be used to send the form data. We use the HTTP GET
method in the above WML example. If you want to use the HTTP POST
method, you should assign the value post to the method
attribute, like this:
<go
method="post" ...>
If
the HTTP POST method is used, the form data to be sent will be placed
in the message body of the request. If the HTTP GET method is used,
the form data to be sent will be appended to the URL. Since a URL can
only contain a limited number of characters, the GET method has the
disadvantage that there is a size limit for the data to be sent. If
the user data contains non-ASCII characters, you should make use of
the POST method to avoid encoding problems.
The
href attribute of the <go> tag specifies the URL to
submit the form data to. In the above WML example, we instruct the
WAP browser to submit the form data to "processing.asp" for
processing when the "Submit Data" anchor link is selected.
Four
<postfield/> tags has been enclosed in the <go></go>
tags in the above WML example. The <postfield/> tag is used to
specify the name-value pairs to be submitted to the server.
The
<postfield/> tag has two attributes, name and value.
As their names suggest, the name attribute specifies the name
of the parameter to be sent and the value attribute specifies
the value of the parameter.
Notice
the difference between HTML and WML here. In HTML, the name
attribute of the <input> and <select> tags is used to
specify the name of the parameter to be sent, while in WML the name
attribute of the <postfield>
tag is used to do the same thing. In WML, the name
attribute of <input> and <select> is used to specify the
name of the variable for storing the form data.
At
the beginning of the above WML document, a value is assigned to the
my_temp_id variable. When the
"Submit Data" anchor link is clicked, it is sent to the
server as part of the form. We use it to simulate the function of a
hidden field in HTML.
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