More About HTML More About WML More About Web Services
Visual DataFlex Web Application Server is capable of doing more than just providing HTML pages to an internet browser. It can also be used to provide Web Services. By making simple URL requests you can support XML based web services using established standard technologies such as as XML, WSDL and SOAP. The Visual DataFlex Web Application Server dynamically generates the WSDL and a set of HTML test pages based on the exposed Web Service methods, letting you concentrate on the functionality of your Web Service rather than low level Web Service details. The Web Service samples are divided in three.
This sample demonstrates a few simple services and how you can easily expose VDF object methods as Web Services. You can extend this sample by creating your own object method and simply publishing it from within the Studio. The Visual DataFlex Web Application Server automatically takes care of the rest, including keeping the WSDL and HTML test pages up to date. You can access the sample from within your browser using the HTML test pages, or you can use a SOAP client such as Visual DataFlex or Microsoft .NET to access the sample using the SOAP protocol. Simply point your SOAP client generator to the WSDL.
HTML Test Page: TestService.wsoThe second sample demonstrates a little more complex Web Service scenario, passing and returning different sets of complex data utilizing struct types and arrays. It allows you to retrieve detailed order information for example.
While many Web Services work with simple data types such as Integer, String and Date, some Web Services may require more complex data. Struct types and arrays are ideally suited for such Web Services. You can define complex struct types, such as a complete order, containing among other things, all order line items as well as shipping address and so forth. The Visual DataFlex Web Application Server automatically takes care of describing your data structure to Web Service clients through the WSDL, allowing various Web Service clients to easily use your Web Service.
HTML Test Page: CustomerAndOrderInfo.wso
WSDL: CustomerAndOrderInfo.wso?WSDL
The third sample demonstrates an alternative for passing and returning complex set of data as pure XML, utilizing the cXmlDomDocument class in Visual DataFlex.
As a lower level alternative to the use of struct types and arrays for complex parameters, you can specify data to be passed as pure XML using cXmlDomDocument objects. This is a very flexible and powerful method which lets you take complete control over each parameter and the return value. Using XmlHandle as a parameter type and/or return type, gives you the flexibility of this powerful feature on individual parameters while also preserving the built-in type serialization/deserialization rules for other parameters and/or the return value using the familiar fundamental VDF data types such as Integer, String and Date, as well as struct types and arrays.
In most cases it's both easier and better to use Struct types and arrays for working with complex data. But sometimes you just need that little extra low-level control and flexibility over a particular parameter or return value, and that's when XmlHandle can be useful.
This sample contains a Web Service to create and return a customer list as pure XML.
HTML Test Page: CustomerXML.wso
WSDL: CustomerXML.wso?WSDL
If you are running a web application that provides web services you will want to run the application with Process Pooling enabled. When Process Pooling is disabled, each web service request requires that a new process gets loaded, initialized, run and then closed. When Process Pooling is enabled a web service request can use a process that is loaded and running in a pool eliminating the time required to load, initialize and close. This is obviously much faster.
You can enable or disable Process Pooling in an application by changing the web application's properties within the Web Application Administrator Utility.
When process pooling is enabled, you have instances of your web application running in a pool. Because these instances have open tables, you will not be able to alter your tables while these processes are running. In other words, you cannot open a table in exclusive mode within the Database Builder utility. Trying to open the table will result in an error. If you need to change the tables, you will need to temporarily disable the Web Application. Web Applications can be enabled and disabled using the Web Application Administrator Utility. Alternately, you may wish to disable process pooling during early development process when you are still changing your tables. If you do this, remember to turn process pooling on before deploying the application (and before running any performance tests).
In this sample, Process Pooling is disabled. This is done to allow you to try out all of the features of Database Builder without needing to disable and re-enable the application. Remember that you would always want to turn process pooling back on before deploying an application that provides web services.
More About HTML More About WML More About Web Services