McAlister Merchant
Microsoft Corporation
March 2001
Applies To: Microsoft Visual FoxPro 7.0
Summary:
Web Services can be available anywhere. You can either create them
yourself or access them over the Web from wherever they happen to be
published. You can use Visual FoxPro to create Web Services, and if you
register them in IntelliSense, Visual FoxPro makes it possible for you
to access them almost automatically. You also can use Visual FoxPro to
access Web Services created in other languages. (6 printed pages)
Contents
Introduction
Web Services
Establishing a Virtual Directory
Creating a Project
Creating a COM Server
Creating and Publishing a Web Service
Registering a Web Service
Using a Web Service
Introduction
Creating
Web Services using Microsoft® Visual FoxPro® 7.0 is a complex process
that involves using Microsoft® Internet Information Services (IIS),
Visual FoxPro COM servers, and Simple Object Access Protocols (SOAP).
You can use IIS, which installs automatically with Visual FoxPro, to
create a virtual directory that references the location on your hard
disk where you place your services.
Then, you can use the Project
manager to create or to compile COM objects. When the COM objects are
created, you can use the Visual FoxPro Web Services wizard to publish
them in your virtual directory.
You can use the IntelliSense
manager to register Web Services with Visual FoxPro, so that the
placement of the Web Service and necessary calling routines in code is
expedited.
This paper walks you through the processes involved
in making Web Services of your existing COM servers and preparing Web
Services for use. From a COM server, you create a very simple Web
Service that is accessible by anyone through HTTP. This Web Service
provides a simple report of the current directory and how many .jpg
files are there.
Web Services
Web
Services extend the accessibility to your own COM servers, as well as
making Web Services from other developers accessible to you through your
browser.
Web Services provide functionality and access to data
between platforms and across diverse connections. You create and use Web
Services to provide or to gain functionality from wherever it happens
to reside. The most important aspect of Web Services is that, because of
the way they use the HTTP protocol and the SOAP proxy, functionality is
available through firewalls. Because HTTP and SOAP are platform
agnostic, Web Services are also platform agnostic. In some cases, this
can provide functionality that was unavailable under COM alone.
To
publish a Web Service, you must create a virtual directory in IIS, and
then create or copy a COM server from which you generate a Web Service
to your virtual directory.
Establishing a Virtual Directory
You
must create or identify a directory into which you will place your Web
Services. Although you can use an existing directory, you might want to
create a separate place on your hard disk to store these files, making
it easier to manage your Web Service files.
To create the virtual directory:
- Create a folder named Web Services in the main Visual FoxPro directory (C:\Program Files\Microsoft Visual FoxPro 7).
- In the Administrative Tools folder of the Microsoft Windows® control panel, double click the Internet Services Manager shortcut.
- The Internet Information Services window opens, displaying a tree in the left pane that shows your hard disk. Expand this node to see available sub folders.
- Select the Default Web Site node in the Tree pane
- From the right-click menu, select New, and click Virtual Directory. This opens the Virtual Directory Creation wizard.
- Follow the steps in the wizard, and specify the Web Services folder that you created earlier as your virtual directory.
You
have created a virtual directory that references the Web Services
folder in which you will store all the Web Services files you create.
Creating a Project
The
Project manager is the most fundamental application-building tool in
Visual FoxPro. Within a Visual FoxPro project, you can assemble
documents of all types, data, classes, code, and other file types. A
project provides access to all the components you might want to include
in a server and contains them for compilation. In this example, you use
the project to compile your Web Service.
To create a project:
- In the File menu, select New.
- In the New dialog box, select Project, and click New file.
- In the Create dialog box, select the Web Services folder you created earlier, and name your project myWServ1.
- Click Save.
Now,
you have created your project in the Web Services folder. This makes it
possible for you to save and compile the project to the correct folder
automatically when you have finished adding components to it.
Creating a COM Server
Because,
a Web Service is a .dll or .exe file, you must use a COM server as the
basis for your Web Service. A COM server in Visual FoxPro is a file with
.dll or .exe extension containing a class built as OLEPUBLIC from a
project. Objects specified as OLEPUBLIC are accessible by Automation
clients. From the .dll file, a new .wsdl file will be generated when you
publish the Web Service. This .wsdl file has the necessary XML code
that describes the classes in the .dll and references which .dll file is
the driving force behind that particular Web Service.
For this
COM server example, you will create a custom class that reports some
very simple information. In this process, you will write a program that
creates the class with two methods and compile the project containing it
into both a COM server and then a published Web Service.
To create a simple class:
- In the File menu, select New.
- In the New dialog box, select Project, and click New file. This opens the Project Manager.
- In the All tab of the Project Manager, expand Code, select Programs, and then click New.
- Copy the following code into the code edit window.
*-- returns curdir() and number of JPEG files
DEFINE CLASS showem AS session OLEPUBLIC
Name = "showem"
PROCEDURE justshow
howmany=ADIR(afilArry,"*.jpg")
IF howmany <1
fileNm="no"
ELSE
fileNm=ALLTRIM(STR(howmany))
ENDIF
X = "about " + CURDIR() + " ... "
Y = "There are " + fileNm + " JPEG files here."
RETURN x + y
ENDPROC
ENDDEFINE
This program defines one class, showem, which has one method, justshow.
- Close the edit window. In the Save As dialog box, name the program myWServ1, and click Save.
- Make sure myWServ1 is set to Main. (You can tell if it is set to Main, because it will be in bold font.) If it is not, in the Project Manager, right-click myWServ1 and click Set Main in the shortcut menu.
To compile the COM server:
- In the Project Manager, click the Build button.
- Select Single-threaded COM server.
- Click OK, and accept the name myWServ1.
Visual FoxPro will compile the
myWServ1 file into a COM server, after which you can turn this COM server into a Web Service.
Creating and Publishing a Web Service
To
add the components necessary to turn your COM server into a Web
Service, you must compile the COM server as a Web Service. After you
specify the settings, Visual FoxPro creates the XML and SOAP files
necessary to turn your server into a Web Service, registers your new Web
Service, and publishes it in your virtual directory.
To compile and publish a Web Service:
- After you have completed the previous procedures and compiled the COM server myWServ1.dll, right-click the Project Manager, and choose Builder from the shortcut menu.
- In the Wizard Selection dialog box, choose Web Services Publisher, and then click OK.
- In the Visual FoxPro Web Services Publisher dialog, use the Ellipsis button (...) to locate myWServ1, and then select the class you want to register from that server. In the COM server you created, myWServ1, you have only one class, showem.
Note It is a good idea to click the Advanced button to make sure the Web Services Publisher
dialog box is referencing the correct files, especially if you have
created similarly-named servers or services in different folders. If the
correct file is not displayed in the drop-down list, use the Ellipsis button (...) to locate the correct file. The IntelliSense scripts
field displays the name under which you (and the SOAP toolkit) will
find this Web Service. After verifying the information in the Advanced Web Services Publisher dialog box, click OK.
- Click the Generate button.
After Visual FoxPro generates the Web Service files, the Web Services
Publishing Results dialog box appears, displaying a list containing the
COM server, .wsdl file, ISAPI or ASP listener, and IntelliSense path
names and compilation results.
At this point, you have created and published your
Web Service. Anyone who has access to the virtual directory you
established earlier can use HTTP to access the Web Service you just
created.
To use this Web Service, someone must write code that
invokes the SOAP client, a listener, and the browser and must employ
several layers of protocol and process. In Visual FoxPro, this is
simplified by registering Web Services in the IntelliSense manager.
Registering a Web Service
You
can register Web Services (both those created by you and those created
by others) in the IntelliSense manager. When you do this, IntelliSense
provides the supporting code whenever you access a registered Web
Service.
To Register a Web Service:
- On the Tools menu, select Intellisense Manager.
- On the Types tab of Intellisense Manager, click the Web Services button to register your new Web Service (your new class also will appear in the Types list).
Now,
IntelliSense will provide your Web Service as an optional selection
whenever you add a strongly typed variable to your Visual FoxPro code.
Using a Web Service
You
use a Web Service the same way you would any COM server to expose
functionality of one application to another application or program. For
example, you can create a Visual FoxPro program that calls the sample
Web Service, myWServ1. In a Visual FoxPro program, declare a strongly
typed variable as in the following line of code, in which you reference
your Web Service, myServ1, by choosing it from the IntelliSense
drop-down list:
LOCAL x AS myWServ1
Visual FoxPro IntelliSense uses the registered information on this Web Service to complete the following lines of code:
x = CREATEOBJECT("MSSOAP.SoapClient")
x.MSSoapInit("http://TheVirtualDisk/web services/ myWServ1.WSDL", , " myWServ1SoapPort")
Then, you call the method of that Web Service just as you do any COM object or class method as in the following code:
? x.justshow()
You can add similar code to access your own or other Web Services to Visual FoxPro programs and applications.
For
more information on Web Services, see "Web Services Overview" in the
Visual FoxPro Help. For more information on COM servers, see "Creating
Automation Servers" in the Visual FoxPro Help.
Prerequisites
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