AdvancED Flex 4

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As you can see from the previous example, you make a service call to retrieve the XML and once you

retrieve the results You set the name space:

var georss:Namespace = new Namespace("http://www.georss.org/georss");

Yoou can than access the results.

Creating a Proxy

The lack of crossdomain.xml can create a scenario where your Flex application works fine on your local

machine but not on your server. The solution for the lack of a crossdomain.xml file is to use a proxy to

connect to the data source and have Flash connect to the proxy instead of the data source directly. By

connecting to a proxy instead of the service, you can access services that don’t allow direct access for

Flash. Web pages can access other open APIs and expose the data for the Flash player. The reason that

using proxy works is that the Flash player allows accessing services from the same domain without the

need to install a cross-domain policy.

There are a few ways to use proxies; one is to create a server-side script to connect to the data source.

Following are three open source examples of proxies that can be used for RESTful POST and GET

methods, as well as for downloading binary data such as SWF files from a remote server. The proxy

scripts will be available for download from the friendsofED site (www.friendsofed.com) as part of the

example files that accompany this book.

PHP proxy

When using a server with PHP, you can usea lightweight open source PHP proxy script that handles two

types of data: RESTful methods of GET and PUT and binary data such as SWF files or images. Keep in

mind that PHP supports the CURL method in order for this script to work.

The following example loads XML/text:

http://yourserver.com/proxy.php?url= 

http://yourserver.com/blog/index.xml

This example loads a SWF (binary data) file:

http://yourserver.com/proxy.php?url= 

http://yourserver.com/files/some.swf& 

mimeType=application/x-shockwave-flash

Here’s the complete code:

<?php

// PHP Proxy

// Responds to both HTTP GET and POST requests

// Author: Abdul Qabiz

// March 31st, 2006

// Get the url of to be proxied

$url = ($_POST['url']) ? $_POST['url'] : $_GET['url'];

$headers = ($_POST['headers'])?$_POST['headers']:$_GET['headers'];

$mimeType =($_POST['mimeType'])?$_POST['mimeType']: 

$_GET['mimeType'];

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//Start the Curl session

$session = curl_init($url);

// If it's a POST, put the POST data in the body

if ($_POST['url']) {

$postvars = '';

while ($element = current($_POST)) {

$postvars .= key($_POST).'='.$element.'&';

next($_POST);

}

curl_setopt ($session, CURLOPT_POST, true);

curl_setopt ($session, CURLOPT_POSTFIELDS, $postvars);

}

// Don't return HTTP headers. Do return the contents of the call

curl_setopt($session,CURLOPT_HEADER,($headers=="true")?true:false);

curl_setopt($session, CURLOPT_FOLLOWLOCATION, true);

//curl_setopt($ch, CURLOPT_TIMEOUT, 4);

curl_setopt($session, CURLOPT_RETURNTRANSFER, true);

// Make the call

$response = curl_exec($session);

if ($mimeType != "")

{

// The web service returns XML.

// Set the Content-Type appropriately

header("Content-Type: ".$mimeType);

}

echo $response;

curl_close($session);

?>

You first get the URL using either POST or GET, then you set the curl request and make the call and

return the XML.

ASP Proxy

When using a server with ASP technology, you can use a lightweight open source ASP proxy script. This

proxy can be used for RESTful services as well as binary data.

Usage:

http://yourserver.com/proxy.asp?url=<url_encoded_desitnation_url> 

[&mimeType=<mimeType>]

Example of using the ASP proxy to download binary data: http://yourserver.com/proxy.asp?url=

http://someserver/1.jpg&mimeType=image/jpg.

Following is an open source script for a server that supports ASP:

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<%

set objHttp = Server.CreateObject("Msxml2.ServerXMLHTTP")

strURL = Request("url")"

objHttp.open "GET", strURL, False

objHttp.Send

If objHttp.status = 200 Then

Response.Expires = 90

Response.ContentType = Request("mimeType")

Response.BinaryWrite objHttp.responseBody

set objHttp = Nothing

End If

%>

The ASP example is pretty straightforward. You set the server URL we are accessing and then we paste

the content on the page.

JSP Proxy

Using JSP technology is similar to ASP. You can set the following proxy to be used for RESTful services

as well as binary data.

The following is an open source script for a server that supports JSP:

<%@ page language="java" contentType="text/html; charset=utf-8"

pageEncoding="utf-8"

import="java.io.BufferedReader,

java.io.InputStreamReader,

java.io.IOException,

java.io.InputStream,

java.net.MalformedURLException,

java.net.URL,

java.net.URLConnection"

private String contentURL;

public static final String CONTENT_URL_NAME = "contentURL";

// get the url through the request:

If (contentURL == null) {

contentURL = (String)request.getAttribute(CONTENT_URL_NAME);

if (contentURL == null) {

contentURL=(String)request.getParameter(CONTENT_URL_NAME);

}

}

if (contentURL == null) {

throw new ServletException("A content URL must be provided, 

as a"'" + CONTENT_URL_NAME + 

"'" request attribute or request parameter.");

URL url = null;

}

try {