FMS 调用 WEBSERVICE（2）

The design goal of any web service is to allow both developers and companies to share data easily. What makes this possible is the ability to output information in standard XML format so that programs written in different languages can communicate with the same service. You can also use your favorite language and platform to interface with Macromedia Flash Media Server 2 from Adobe.

Web services on the server side allow you to interact with your production servers without ever exposing the connection. By being free to develop in the language you want and still communicate with Flash Media Server,all you need to do is create a web service.

Flash Media Server 2 has some limitations on how web services handle complex data (objects) or an array returned by a web service. After some serious head scratching,I have attempted to draw out some of these limitations and describe to what extent you can still manipulate complex data types.

By way of example—a web service providing a weather forecast using the Web Service Description Language (WSDL)—this article attempts to explain not only how web services work in Flash Media Server 2 but detail some of the challenges you face when dealing with complex data types.

In this section,I will go over the interface and the parameters required for the remote method.

There are many free web services on the Internet (XMethods,?WebserviceX.net,and so on). I will use one of the WebserviceX.net services for this article (see Figure 1).

The end user simply submits a five-digit ZIP code to the service. There's no real error handling built in. When results are displayed,the Next and Prev buttons step the user through the upcoming days in the forecast.

Because there is a limit to the amount of data that Flash Media Server can receive from a web service,you may get mixed results with this weather forcast application. This web service provides a seven-day forecast but you will notice that,in most cases,you get a five-day forecast due to this limitation. The other result you may receive is an "Unable to connect to endpoint" message.

Note:?If you do receive an "Unable to connect to endpoint" message,enter a new ZIP code and try again. There is no need to recompile the client application or unload the server ASC file. Alternate between ZIP codes 33021,77077,33004,33309,77079,94105,10286,and 97070. Of course,you can use your own ZIP code—just remember that this is a free service and is not always available.

Point your browser to the following URL,which shows the XML structure definition for the Weather Forecast WSDL (see Listing 1). You should be able to see other methods that you could use,like?GetWeatherByPlaceName,which requires a parameter?PlaceName?of type?string:

For this exercise,I will focus on?GetWeatherByZipCode,which requires a parameter of type?string.

Listing 1.?Weather Forecast WSDL

On the server side,make sure you start by loading the?WebServices?class with the following:

In this particular example,you are using remote method invocation (RMI) from the client to the server methodgetWeather:

Then you need a var of type?string?and?array?as well as the path to your service:

Instantiate the?WebServices?class as follows,passing in the path to your service:

Keep in mind that the?WebServices?class of Flash Media Server 2 provides you with two event handlers:?onLoad?andonFault?for both the WSDL and the result.

So you could use the following:

Once your?WebService?object is set,you need to fire an event on it using a function provided by the web services provider. Pointing your browser to the WSDL URL,you can view the XML definition as well as other descriptions. This allows you to view all available methods and their corresponding results.

As shown in Listing 1,pointing the browser to the URL reveals which methods are available to call within the XML code definition presented by the browser and how they will return the results.

Currently,you are concerned with the?GetWeatherByZipCode?method:

Once your method is called,you need to parse the result when?onResult?is triggered:

This process is rather elementary. All you're doing is working around the current?WebServices?class to handle an array. You use a "for in" loop to grab each element in the xmlNodes—part of the Details result—and pass it into the?aDetailarray you created earlier:

Once you have passed in all nodes,you can manipulate the array directly. Keep in mind that every web service returns results in its own way,so it is important to find a way to unfold your result. I have found that the most reliable way is to use the "for in" loop. Applying a "for in" loop showed some promise to the wealth of data returned. I then found other objects and set up "for in" loops in them,as well,until I had all the data I needed.

Note:?If you handle the processing on the client side,the "for in" loops will read backwards. Therefore,it is important to reverse the array (using?array.reverse()),once you have pushed the nodes into the array,to correct the order.

At this point you could use just the array to do what you want but my main objective is to get the data into its proposed XML format:

Push each node into the?Detailing?string and send to the client:

As you may be able to determine in Figure 1,I used three buttons ("Prev," "Next," and "Get Forecast"),a text input field (z_text),and a text area (T_text):

• prev?button has the label "prev"
• dnxt?has the label "next"
• B?has the label "Get Forecast"
• z_text?input field is for the ZIP code
• T_text?text area displays the output information

In the Main.as class I have the following:

which passes results to its own?ReturnForcast?method:

Once?ReturnFunction?uses the Flash Media Server string to create your XML,you can manipulate it into an array to be processed by?showWeather(). As I stated earlier,you could have also just sent the initial array from the server:

To make the actual remote method call from the client,use the?B("Get Forecast")?button's?click?event:

Your final client-side code should look like this:

Your final server-side code should look like this:

Where to go from here

This simple example should provide you with a better idea of the web services limitations that you will encounter. Having taken the time to explore the possibilities,however,you can see that when you use Flash Media Server 2,you have the freedom to interface with not only any language but with any result set as well.

For more information,check out the following resources for various technologies:

• .NET:?Top Five ASP.NET Web Services Tips?(Alex Ferrara,O'Reilly)
• ColdFusion:?Publishing Web Services?(from?Developing ColdFusion MX Applications with CFML,ColdFusion LiveDocs)
• ColdFusion:?Programming ColdFusion MX: Web Services?(from?Programming ColdFusion MX,2nd Edition,O'Reilly)
• Java:?Developing Web Services with Java 2 Platform,Enterprise Edition (J2EE) 1.4 Platform?(Qusay H. Mahmoud,Sun Developer Network)
• PHP:?Creating and Consuming Web Services with PHP?(Jean-Luc David,XML.com)
• Ruby:?REST on Rails?(Matt Biddulph,XML.com)

You may also wish to read up on?XML-RPC,a "spec and set of implementations that allow software running on disparate operating systems,running in different environments to make procedure calls over the Internet."