Performing the Transformation

XML Streams Module User's Guide
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6.3 Performing the Transformation

This transformation example uses a simple object named book. This object simply holds an author name and a book title. For the complete example, see buildspace\examples\xmlstreams\xsltTransform\xsltTransform.cpp.

This example is based on the examples used in Chapter 5.

class book 
{
   public:
     book ();
     book (const RWCString& title, const RWCString& author);
   private:
     RWCString title_;
     RWCString author_;
};

This section discusses the main() function for the example. The explanation is broken into three parts:

creating a book object and serializing it to a file using an XML stream that applies a transformation to make the resulting XML more readable
reading the file back in and restoring the book object using an XML stream that applies a transformation to restore the original XML format
printing out both the original XML streams data for the book object and its more readable, transformed version

6.3.1 Serializing the book Object to a File

First, create a book object and serialize it out to a file. Because the XML format generated by XML streams is difficult to read, you transform the output stream into a more easily-readable format.

int main()
{
   using std::ofstream;                                         //1
   using std::ifstream;
   using std::cout;
   using std::endl;

   book book1("To Love and Be Wise","Josephine Tey");           //2
   book book2;

   XMLPlatformUtils::Initialize();                              //3
   XalanTransformer::initialize();                              //4

   {
     ofstream fout("book.xml");                                 //5
     ifstream script("../XmlStreamOut.xsl");                    //6

     RWObjectOutputStream out =                                 //7
       RWXsltObjectOutputStreamImp::make(fout,script);
     out << book1;                                              //8
     out.flush();                                               //9
   }

`//1`	Indicates that certain variables refer to their counterparts in the STD namespace.
`//2`	Creates two *book* objects, one with data, one to hold the data when you restore the object later on.
`//3`	Initializes the Xerces XML parser, required by the Xalan transformation engine. The use of other XSLT processors may require the initialization of a different parser.
`//4`	Initializes the Xalan transformation engine.
`//5`	Creates an *ofstream* for writing character data to a file.
`//6`	Creates an *ifstream* for reading in the output XSLT stylesheet.
`//7`	Sets up an XML output stream that includes support for a transformation by passing the *ifstream* to the output XSLT stylesheet.
`//8`	Serializes the *book* object to a file.
`//9`	Flushes the output buffer for the XML stream, transforming the XML in the process. You may perform this step explicitly, as it is performed by this line, or you may allow it to occur implicitly when the destructor calls `flush()`, and the output stream goes out of scope. Initialize the processor (in this example, Xalan) only once for a given process, no matter how many transformations are performed.

6.3.2 Restoring the book Object

At this point you have written the book object XML data to the file book.xml. Next you are ready to restore the object, which involves:

reading in the file book.xml
transforming the XML back to the form required by XML streams

restoring the object as book2

   {
     ifstream fin("book.xml");                                  //1
     ifstream script("../XmlStreamIn.xsl");                     //2

     RWObjectInputStream in =                                   //3
       RWXsltObjectInputStreamImp::make(fin,script);
     in >> book2;                                               //4
   }

`//1`	Creates an *ifstream* for reading in the object data.
`//2`	Creates an *ifstream* for reading in the input XSLT stylesheet.
`//3`	Sets up an XML input stream that includes support for a transformation by passing the *ifstream* to the input XSLT stylesheet.
`//4`	Restores the *book* object as the *book2* instance create earlier, transforming the XML back to the expected XML format in the process.

6.3.3 Examining the XML Output

Finally, the example writes to standard out two forms of the serialized object:

the transformed, more readable version

the form created by the XML serialization and expected by XML streams when the object is restored

   {
     ifstream script("../XmlStreamOut.xsl");                   //1
     RWObjectOutputStream out =                                //2
       RWXsltObjectOutputStreamImp::make(cout,script);
     out << book2;                                             //3
   }
   cout << endl;
   {
     RWObjectOutputStream out =                                //4
       RWXmlObjectOutputStreamImp::make(cout);
     out << book2;                                             //5
   }
   return 0;
}

`//1`	Creates an *ifstream* for reading in the output XSLT stylesheet.
`//2`	Sets up an XML output stream that includes support for a transformation by passing the *ifstream* to the output XSLT stylesheet.
`//3`	Streams the transformed version of the *book2* object to standard out.
`//4`	Sets up an XML output stream with no transformation support.
`//5`	Streams the standard XML streams version of the *book2* object to standard `out`.

Here is the resulting output:

With transformation:

<?xml version="1.0" encoding="UTF-8"?>
<book xmlns:rw="http://www.roguewave.com/xmlstream" 
  xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
  xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance"
  xsi:type="book">
    <title xsi:type="xsd:string">To Love and Be Wise</title>
    <author xsi:type="xsd:string">Josephine Tey</author>
</book>

Without transformation:

<?xml version="1.0" standalone="yes"?>
  <rw:nested_object rw:class="book" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" 
xmlns:rw="http://www.roguewave.com/xmlstream">
    <rw:member rw:name="title" xsi:type="xsd:string">To Love and Be
        Wise</rw:member>
    <rw:member rw:name="author" xsi:type="xsd:string">Josephine
        Tey</rw:member>
</rw:nested_object>

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