Introduction
Recently, I have been doing a lot of reading on SOAP
and trying to familiarize myself with the MS SOAP Toolkit (version SP2). The
samples that come with the toolkit are pretty neat, in that they have quite a
bit of C++ samples too. As with any distributed application the fun lies in
passing complex types as arguments to methods over the wire as opposed to
primitive data types. In this article I have provided an implementation of the
ISoapTypeMapper interface in C++ (using ATL)�
for serializing custom objects into XML and sending them over the wire
using SOAP. This article assumes that the reader is familiar with SOAP, ATL and
with the set up of IIS for running the SOAP apps and has the MSSOAP toolkit SP2
installed.
The project
This project, as will be evident, is made up just to
illustrate the implementation of the ISoapTypeMapper interface in C++ for
complex objects. The aim of this article is to show you how to serialize two
COM objects (namely Address and Dealer) into XML and send them over the wire
using SOAP. The description of the two objects is shown below :
- The
Address
object has 5 properties namely "Name", "Street",
"City", "State" and "Zip" all defined as strings.
- The
Dealer
object has 2 properties namely "Id" as string and "Address"
as the above defined "Address" object.
The VC++�
project shows the implementation of these objects and also the
implementation of 2 other objects namely AddressMapper and DealerMapper which actually implement the
ISoapTypeMapper interface
and help in serializing the "Address" and "Dealer" objects
respectively into XML.
There are two VB projects one called
CPlusPlusAddress.vbp and the other Client.vbp. The CPlusPlusAddress.vbp is an
ActiveX DLL project which is the Web Service implementation. It basically
consists of 4 methods whose functionality is defined below:
ProcessAddress - accepts an Address object as parameter and return a String
which is actually a
concatenation of all strings which make up the Address object.
EchoAddress -- accepts an Address object as parameter and returns the same the
Address object.
ProcessDealer -- accepts a Dealer object as parameter and return a String
which is actually a
concatenation of all strings which make up the Dealer object.�������
EchoDealer -- accepts a Dealer object as parameter and returns the same the
Dealer object.
The other VB project Client.vbp is a standard EXE and
invokes the methods exposed the CPlusPlusAddress Web Service.
Getting Started
First compile the C++ project which actually registers
the type mappers and the Address and Dealer COM objects used by the Web Service
and the client. Then compile the CPlusPlusAddress.vbp project and ideally you
will need to generate the .wsdl and .wsml files. But the project contains the
files in the WSDL folder. Make sure create a virtual directory in IIS and name
it CPPAddress. This virtual directory must actually point to the
WSDL folder which contains the wsdl and wsml files. Then compile the Client.vbp
project and you should be able to run the application.
The AddressMapper object
The code for the AddressMapper object is pretty self
explanatory. The workings of the relevant individual methods of the ISoapTypeMapper interface are explained below:
Init() - Since the all properties in Address object
are strings we simply retrieve the string mapper that comes with Soap toolkit
and store it in the m_pStringMapper element.
read() - the read method just reads the values in the
incoming node object and builds an Address object with the values and return
it.
write() - the write methods reads the values of the
individual properties of the Address object and writes the XML to be sent over
the wire.
The DealerMapper object
The workings of the DealerMapper object are similar to
that of the AddressMapper object. The DealerMapper object uses the
AddressMapper object to serialize/deserialize the Address part of the Dealer
object.
Conclusion
The article itself doesn't do much more than describe
the projects that make up the code. The code is very self explanatory. I
decided to do this since I found a lot of queries regarding serializing complex
data types using C++, which went unanswered in the SOAP mailing lists
maintained by Develop Mentor. I spent 2-3 days just trying to find an
implementation on the Internet. I hope this sample helps the other folks like
me who are frustrated (the way I was ) on not being able to find pointers on
doing this using VC++/ATL.
