Posting Form Data

indexadjustmentInternet και Εφαρμογές Web

13 Νοε 2013 (πριν από 4 χρόνια και 4 μήνες)

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Posting Form Data

Pp 167..., Corejava

Sending Info from Browser to Server

When user clicks Submit button, text in text fields
and clickbox settings, etc, are sent back to web

Web server calls a program that processes user

Many techs enable web servers to call programs

Java servlets

JavaServer Faces

Microsoft ASP

CGI scripts in Perl, C++, or whatever language

Will call them all “scripts”!!!

not nice!!

Commands (“methods”) to send info
back to server

We won't discuss server
side scripts but just
how to send info to server

Two commands commonly used are POST and

GET is easier, simply attach params to the end
of the URL



For example, Yahoo has a script, py/, at
the host

Scripts requires 2 params, addr and csz

You separate the params by an & (ampersand)
and encode the parameters using URL Encoding

Replace all spaces with a +

Replace all nonalphanumeric chars by a % followed by
a 2
digit hex number (ASCII code)

S. Main is S%2e+Main

Because hex 2e is the period in ASCII code

Try requesting

POST command

GET is easy but often limited (visible, short)

In POST, you don't attach params to a URL

Instead, you get an output stream from the

Then write name/value pairs to the output

Still have to URL
encode the values and
separate them with & character

Generic Example of POST

URL url = new URL(“

URLConnection connection = url.openConnection();

connection.setDoOutput(true); //default is input from server to

PrintWriter out = new

//PrintWriter good for sending text to server

out.print(name1 + “=” + URLEncoder.encode(value1, “UTF
8”) + “&”);

out.print(name2 + “=” + URLEncoder.encode(value2, “UTF


Then, call getInputStream and read the server resposne.

See the PostTest example.