Flex and Web Services

Its always fun to work with Web service in Flex. Those pesky headers! Found a couple of terrific links on the subject. Now its easy :-)
http://www.actionscript.org/forums/showthread.php3?t=195916&highlight=e4x+faq
http://craigkaminsky.blogspot.com/2009/05/flex-3-make-net-namespaces-in-soap-xml.html

Just to put some code behind this....

Here is part of the feed:

<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
<feed xml:base="http://www.placespr.com/WebDataService1.svc/" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns="http://www.w3.org/2005/Atom">
<title type="text">ptg_categories</title>
<id>http://www.placespr.com/webdataservice1.svc/ptg_categories</id>
<updated>2009-11-22T15:26:36Z</updated>
<link rel="self" title="ptg_categories" href="ptg_categories" />
<entry>
<id>http://www.placespr.com/WebDataService1.svc/ptg_categories(1)</id>
<title type="text" />
<updated>2009-11-22T15:26:36Z</updated>
<author>
<name />
</author>
<link rel="edit" title="ptg_categories" href="ptg_categories(1)" />
<category term="ponce_1000Model.ptg_categories" scheme="http://schemas.microsoft.com/ado/2007/08/dataservices/scheme" />
<content type="application/xml">
<m:properties>
<d:cat_id m:type="Edm.Int32">1</d:cat_id>
<d:name m:null="true" />
<d:service>hotels.asmx</d:service>
<d:icon>/images/icons/hotels.gif</d:icon>
<d:ordering m:type="Edm.Int32">1</d:ordering>
<d:counting m:type="Edm.Int32">75</d:counting>
</m:properties>
</content>
</entry>
......


and here is the modified code from these excellent links:

private function getCategoriesResult(evt:ResultEvent):void {
var respXML:XML = evt.result as XML;

var xmlSource:String = respXML.toXMLString();
//Strip off the headers
xmlSource = xmlSource.replace(/<[^!?]?[^>]+?>/g, removeNamspaces); // will invoke the function detailed below
var cleanXML:XML = XML(xmlSource);
for each( var item:XML in cleanXML.entry ) // looping over the reportHistory elements to act on them
{
trace( "name: " + item.content.properties.service);
}
}

// Web service response cleaner function
private function removeNamspaces(...rest):String
{
rest[0] = rest[0].replace(/xmlns[^"]+\"[^"]+\"/g, "");
var attrs:Array = rest[0].match(/\"[^"]*\"/g);
rest[0] = rest[0].replace(/\"[^"]*\"/g, "%attribute value%");
rest[0] = rest[0].replace(/(<\/?|\s)\w+\:/g, "$1");
while (rest[0].indexOf("%attribute value%") > 0)
{
rest[0] = rest[0].replace("%attribute value%", attrs.shift());
}
return rest[0];
}

IE8 Vista Problem

I'll not br rotten about Microsoft, since I develop on Windows .. but sometimes!!

I found I could not open IE, out of the blue. Spent a frustrating couple of hours troubleshooting. All to do with security updates and IE settins. The solution which worked of me is as follows:

Open internet explorer and go to menu TOOLS, than to INTERNET OPTIONS. Open the CONNECTION tab,and click on SETTINGS. You then uncheck the 'use of proxy server for this connection' and click ok .

AlivePDF

Its been a hectic time with project work. Much to share particularly with regards the ArcGIS Flex API and the open source OpenScales Flex library.

Just a quick mention today on AlivePDF. Historically, I've had to generate PDF's in PHP. AlivePDF is based on the PHP library FPDF. It makes generating PDF's from Flex very straighforward. Alex Britez has written a simple example here.

Open Source GIS Clients

I have had a number of companies recently approach me about open source GIS options. This has something to do with my recently published articles. One interesting area has been an investigation into Flex GIS clients. Openlayers is the premier Web 2.0 GIS client; well supported, a rich library filled with an array of functionality .. but written in Javascript. Now I have nothing against Javascript, its free, has a big community behind it and runs in the browser. But I'm a Flex developer. I prefer it because .. it has an excellent IDE which makes for easy debugging, developing sophisticated interactive application is both quick and easy, applications run the same in all browsers, actionscript is object oriented. Actionscript is just nicer and easier to work with .. in my view.

So enough. Anybody who argues against these opinions I would not oppose. Its just how I feel about it. Anyway, the whole Flex GIS open source client issue. I have worked with Modest Maps for sometime now to develop mostly consumer maps. Stop right there! Consumer maps? The world of online maps remains somewhat split. GIS maps and consumer maps. Consumer maps I define as the use of basemaps - tiles which are derived from satellite images or vector road maps for example - to build mash ups; video, imagery, text using, often, the addition of map markers for access (or clickable icons geospatially placed on the map). Here is a simple example. Google, Yahoo, Bing, mapquest offer largely API's for developing consumer maps.

So what are online GIS maps. A simple question? Well maybe. GIS has moved from the desktop to the Web. It was very much a niche market. Geography type nerds generating applications and analyses in large part for government (a generalisation but close to reality). The frustration for GIS vendors was how do they broaden the market. ESRI and the other key private vendors struggled to sell into the enterprise. They still do in fact.

Suddenly google maps arrived on the scene. It shook the mapping industry to its core. Internet maps were everywhere. Its worth noting that Mapquest preceded Google, but the fanfare (and $) waited for Googles arrival. Suddenly the other GIS vendors needed to react. ESRI produced rival online products. But with a GIS twist.

So here we are today. A plethora of consumer map APIs. And ESRI sitting in a somewhat awkward position offering free API's hooking easily into their own server product(s) ArcGIS (not so easily into other providers). Offering consumer and GIS API functionality. With a focus to sell their complete stack to those interested. Their purpose is to make money.

So how about those of us wanting to build online GIS maps, but avoid the high cost of the private vendor solutions? The open source GIS stack is very mature. But how about Flex clients?

I've spent some time looking at the options. Base requirements include:

- Rendering both WFS and WMS in combination
- Overlays of these services on various basemaps
- Drawing tools for line point and polygons
- Identify functionality

I looked at both Modest Maps and OpenScales. Though not its focus there has been some work done on Modest Maps toward some level of interaction with spatial servers. I added a WMS layer at:

http://www.flexmappers.com/mapserving/mapservingWMS/

Note, I had to make some tweeks to the WMS provider, provided with the library.

Openscales is less mature. But very impressive for how long development has been underway. I built the following map application:
http://www.flexmappers.com/mapserving/openscales.html

It supplies much of the base functionality I was looking to include. WMS is proving a little challenging (but i suspect a style tag is mssing from the tile request) and the map interaction is not a smooth as Modest maps. Only openstreetmap is provided, but I am looking to port code from Modest maps to add this functionality.

Ultimately Flex should simply be rendering the points, lines, and polygons supplied by the server.

I am interested to see how easy it might be to port from one library to the other. Either way, Openscales is a very interesting project. One well worth supporting.

Flex and PHP POST

I always forget the syntax when trying to get around the Flex sandbox and use PHP. On the Flex side we need the following:

[Bindable]private var pr_url:String;

..
private function init():void
{
..
pr_url = "url to SOAP service for example";
pr.send();
}

..

<mx:HTTPService id="pr" resultFormat="e4x" result="getMonths_result(event);" fault="getMonths_fault(event);" method="POST" url="http://www.flexmappers.com/puertorico/test.php">
<mx:request xmlns="">
<url>
{pr_url}
</url>
</mx:request>
</mx:HTTPService>

On the PHP side:

<?php

header('Content-Type: text/xml');
$url = $_POST["url"];

$data = file_get_contents($url);
echo $data;
?>

OpenScales

While becoming increasingly more impressed with Openlayers I came across OpenScales. A porting of sorts of Openlayers to Actionscript 3.0. Some key links below:

My OpenStreetmap, WMS, WFS Test
http://www.flexmappers.com/openscales

Code Examples
http://openscales.org/svn/openscales/trunk/openscales-fx-examples/src/main/flex/

Demo
http://openscales.org/openscales.swf

api
http://openscales.org/mvn-site/
http://openscales.org/mvn-site/openscales-core/asdoc/index.html

GetCapabilities Test
http://openscales.org/proxy.php?url=http://sigma.openplans.org/geoserver/ows?service=WFS%26request%3DGetCapabilities

PostGIS

Here is an excellent guide to working with PostGIS. Some of my additional notes:

Load Shapefile to PostGIS

a) DB Connect:
psql -d gisdb -h localhost -U matt

b) Generate sql file from shapefile:

C:\Program files\PostgreSQL\8.2\bin>shp2pgsql.exe data\states > states.sql

c) Use pgAdmin to ru sql (tools -> query tool. In query tool open->go to the states.sql

Paul Ramsey wrote PostGIS. I recently shared some emails with him. Thought part of the discussion worth reprinting:

Q. What is the difference between PostGIS and ArcSDE?

A. At a very high level (or perhaps this is a very low level), PostGIS /
PostgreSQL is a database, and ArcSDE is not. ArcSDE is a "spatial
middleware", it runs as a separate process and talks to the real
database below it. PostGIS is a "dynamically loadable runtime" inside
the PostgreSQL process -- it runs inside the same address space as
PostgreSQL, from the point of view of the computer, it's the all the
same program.

PostGIS should be viewed in exactly the same way relative to
PostgreSQL as Oracle Spatial should vis-a-vis Oracle, SQL Server
Spatial vis-a-vis SQL Server, Informix Spatial Extender vis-a-vis
Informix, etc, etc, etc. It works exactly the same way as all those
other in-process spatial type extensions to relational databases. So,
call it an "extension", a "spatial type", a "data blade", etc.
Unfortunately, years of marketing by various vendors have muddied the
terminological water surrounding type extension mechanisms.

The most important functional differences with SDE have nothing to do
with spatial database functionality and everything to do with ESRI
product placement and marketing. You'll find that ESRI products talk
more directly to ArcSDE than they do to PostGIS (or Oracle Spatial or
SQL Server Spatial, for that matter) because ESRI is interested in
selling their whole stack (desktop + server + web apps) to their
clients, not just the ArcGIS component. It's a non-trivial benefit for a customer that (a) already has a lot of ESRI software and (b) can afford the maintenance overhead in dollars, time and expertise that ArcSDE extracts.