5.2 Transforming your XML Documents
This section describes how to transform your XML documents.
5.2.1 Overview of the Transformation Process
The following sections illustrate how to perform both character-based and element-based transformations, using an object book.
The steps included in this section include:
adding serialization support (for more information, see
Chapter 3)
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
5.2.2 Adding Serialization Support
The object book holds an author name and a book title.
First, you will instantiate book, and add serialization support. This process is identical for both transformations.
class book
{
public:
book ();
book (const RWCString& title, const RWCString& author);
private:
RWCString title_;
RWCString author_;
};
As described in the example in
Chapter 5, you must add macros to the header and implementation files to prepare the object for serialization.
To the header file, add the macro R
W_DECLARE_VIRTUAL_STREAM_FNS(), which defines the
streamContents() member function:
class book
{
RW_DECLARE_VIRTUAL_STREAM_FNS(book)
public:
book ();
book (const RWCString& title, const RWCString& author);
private:
RWCString title_;
RWCString author_;
};
Add to the header file:
// Add serialization support
RW_DECLARE_STREAMABLE_AS_SELF(book)
RW_DECLARE_STREAMABLE_POINTER(book)
To the implementation file, first add macros that define insertion and extraction operators for the class members:
// Define how book will be serialized
RW_BEGIN_STREAM_CONTENTS(book)
RW_STREAM_ATTR_MEMBER(title,title_)
RW_STREAM_ATTR_MEMBER(author,author_)
RW_END_STREAM_CONTENTS
Then add macros that allow the book object itself to be serialized as a pointer reference:
// Allow a reference to a book to be serialized
RW_DEFINE_STREAMABLE_POINTER(book)
RW_DEFINE_STREAMABLE_AS_SELF(book)
5.2.3 Serializing the book Object to a File
Next, you serialize your book object out to a file. Because the XML format generated by XML streams is difficult to read, transform the output stream into a more readable format.
Each of the following sections considers first a character-based C++ transformation, followed by an element-based C++ transformation.
5.2.3.1 For a Character-based C++ Transformation
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;
MyInStreamTransform inTransform; //3
MyOutStreamTransform outTransform; //4
{
ofstream fout("book.xml"); //5
RWObjectOutputStream out = //6
RWTTransformObjectOutputStreamImp<MyOutStreamTransform>
::make(fout,outTransform);
out << book1; //7
out.flush(); //8
}
5.2.3.2 For an Element-based C++ Transformation
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;
MyInParsedTransform inTransform; //3
MyOutParsedTransform outTransform; //4
{
ofstream fout("book.xml"); //5
RWObjectOutputStream out = //6
RWTParsedObjectOutputStreamImp<MyOutParsedTransform>
::make(fout,outTransform);
out << book1; //7
out.flush(); //8
}
5.2.4 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.xmltransforming the XML back to the form required by XML streams
restoring the object as
book25.2.4.1 For a Character-based C++ Transformation
{
ifstream fin("book.xml"); //1
RWObjectInputStream in = //2
RWTTransformObjectInputStreamImp<MyInStreamTransform>
::make(fin,inTransform);
in >> book2; //3
}
5.2.4.2 For an Element-based C++ Transformation
{
ifstream fin("book.xml"); //1
RWObjectInputStream in = //2
RWTParsedObjectInputStreamImp<MyInParsedTransform>
::make(fin,inTransform);
in >> book2; //3
}
5.2.5 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
5.2.5.1 For a Character-based C++ Transformation
{
RWObjectOutputStream out = //1
RWTTransformObjectOutputStreamImp<MyOutStreamTransform>
::make(cout,outTransform);
out << book2; //2
}
cout << endl;
{
RWObjectOutputStream out = //3
RWXmlObjectOutputStreamImp::make(cout);
out << book2; //4
}
return 0;
}
Here is the resulting output:
With transformation:
<?xml version="1.0" encoding="UTF-8" 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>
Without transformation:
<?xml version="1.0" encoding="UTF-8" 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>
5.2.5.2 For an Element-based C++ Transformation
{
RWObjectOutputStream out = //1
RWTParsedObjectOutputStreamImp<MyOutParsedTransform>
::make(cout,outTransform);
out << book2; //2
}
cout << endl;
{
RWObjectOutputStream out = //3
RWXmlObjectOutputStreamImp::make(cout);
out << book2; //4
}
return 0;
}
Here is the resulting output:
With transformation:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<book xmlns:rw="http://www.roguewave.com/xmlstream"
xsi:type="book"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance">
<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" encoding="UTF-8" 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>